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A nuclear magnetic resonance study of poly(ether ether ketone) and poly(polyphenylene sulfide) Clark, Jane N. 1986

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A NUCLEAR MAGNETIC RESONANCE STUDY OF POLY(ETHER ETHER KETONE) AND POLY(PHENYLENE SULFIDE)  BY  JANE B.Sc.  N.  CLARK  ( E n g . ) , Queen's U n i v e r s i t y  at Kingston,  1983  A THESIS SUBMITTED I N PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE  IN  THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF CHEMISTRY  WE ACCEPT THIS THESIS AS CONFORMING J O THE REQUIRED STANDARD  THE UNIVERSITY OF B R I T I S H COLUMBIA JUNE, 1986  ©  J.N.  Clark,  1986  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of  requirements f o r an advanced degree at the  the  University  o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make it  f r e e l y a v a i l a b l e f o r reference  and  study.  I further  agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may  be granted by  the head o f  department or by h i s or her r e p r e s e n t a t i v e s .  my  It i s  understood t h a t copying or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l gain  s h a l l not be allowed without my  permission.  Department of The U n i v e r s i t y of B r i t i s h 1956 Main Mall Vancouver, Canada V6T  1Y3  Date  E-6  (3/81)  Columbia  written  ii  ABSTRACT  Poly(ether  ether ketone),  are both polymers  PEEK, a n d p o l y ( p h e n y l e n e  o f commercial importance on account o f  t i o n as m a t r i x m a t e r i a l s  for  composites.  sulfide), their  applica-  Amorphous a n d c r y s t a l l i n e  o f b o t h p l a s t i c s have been s t u d i e d by n u c l e a r magnetic resonance troscopy:  high resolution  1 3  C  The h i g h r e s o l u t i o n the a i d of lines  of  Unity  the d i p o l a r  the sample, w i t h the f u l l y  time f o r  experiment  spec-  PMR.  The w i d t h o f  t h e CP/MAS s p e c t r a w e r e s e e n t o b e p r o p o r t i o n a l  of  forms  the polymers were a s s i g n e d  dephasing technique.  The v a r i a b l e - c o n t a c t - t i m e contact  CP/MAS a n d w i d e - l i n e spectra of  PPS,  the to  with  resonance the  crystal-  amorphous s p e c t r a b e i n g t h e  widest.  for  optimum  t h e amorphous f o r m i s  PEEK i n d i c a t e d t h a t  shorter  than that  the  of  the  crystal-  line. Variable  temperature  l i n e w i d t h and s p i n - l a t t i c e  m e a s u r e m e n t s w e r e made o n b o t h t h e c r y s t a l l i n e the polymers.  The t e m p e r a t u r e  and amorphous f o r m s  r a n g e was a m b i e n t t o 4 4 0 K .  s p e c t r a a p p e a r e d as a b r o a d l i n e w i t h a n a r r o w c o m p o n e n t Except  i n t h e c a s e o f PPS a b o v e t h e T g ,  more i n t e n s e . relaxation  Partially  times  for  t h e two components. at a l l  t h a n t h e amorphous.  narrowing at  the glass  The  maximum r e l a x a t i o n t i m e s  the c r y s t a l l i n e  temperature.  All  i n the glass t r a n s i t i o n  showed  samples  region.  the  separate  L i n e w i d t h measurements  The a m o r p h o u s l i n e w i d t h s  transition  proton  t h e b r o a d l i n e was b y f a r  temperatures  of  superimposed.  r e l a x e d s p e c t r a b e l o w Tg i n d i c a t e d  made o n t h e b r o a d l i n e : broader  relaxation  were  s p e c t r a were abrupt displayed  i i i  Differential  s c a n n i n g c a l o r i m e t r y was e m p l o y e d t o c o m p l e m e n t  NMR d a t a . The m e l t i n g ,  glass  t r a n s i t i o n and c r y s t a l l i z a t i o n  the  temperatures  w e r e m e a s u r e d b y DSC. A n a t t e m p t was made t o c o r r e l a t e  the r e s u l t s  morphology and m o l e c u l a r m o t i o n a l b e h a v i o u r  of  of  the study w i t h  t h e two  polymers.  the  iv  TABLE OF CONTENTS  Page  ABSTRACT  ii  L I S T OF TABLES  viii  L I S T OF FIGURES  ix  ACKNOWLEDGEMENTS  xii  1.  2.  INTRODUCTION  1  1.1  General I n t r o d u c t i o n  1  1.2  The O r g a n i z a t i o n o f  the Thesis  MATERIALS 2.1  2.2  2.3  5  6  History  and S y n t h e s i s  6  2.1.1  Poly(ether  6  2.1.2  Poly(phenylene  ether ketone) sulfide)  8  Morphology and P r o p e r t i e s  9  2.2.1  Poly(ether  9  2.2.2  Poly(phenylene  ether ketone) sulfide)  20  The M a t e r i a l s U s e d i n T h i s Work  23  2.3.1  Poly(ether  23  2.3.2  Poly(phenylene  ether ketone) sulfide)  23  V  3.  THERMAL ANALYSIS: DIFFERENTIAL SCANNING CALORIMETRY  24  3.1  Thermal A n a l y s i s Theory  24  3.2  DSC Work b y O t h e r s PEEK a n d PPS  26  3.3  Experimental  26  3.4  Results  and D i s c u s s i o n  28  3.4.1  The G l a s s T r a n s i t i o n  31  3.4.2  Crystallization  33  3.4.3  Melting  35  3.5  4.  . . .  Summary o f DSC Work  HIGH RESOLUTION  1  3  C NMR STUDIES  4.1  Introduction  4.2  Solid State  4.3  4.4  35  37  t o CP/MAS NMR  1 3  C NMR T h e o r y  37  .  40  4.2.1  The E n e r g y I n t e r a c t i o n s  40  4.2.2  The CP/MAS E x p e r i m e n t  45  4.2.3  Variations  o n t h e CP/MAS E x p e r i m e n t  . . .  52  Experimental  54  4.3.1  Rotors  54  4.3.2  Set-Up  55  4.3.3  P u l s e Programs  56  Results  and D i s c u s s i o n  56  4.4.1  Poly(phenylene  sulfide)  56  vi  4.4.2  4.5  5.  ether ketone)  Summary a n d C o n c l u s i o n s  61  o f CP/MAS Work  71  W I D E - L I N E PROTON NMR STUDIES  73  5.1  Introduction  73  5.2  S o l i d S t a t e P r o t o n NMR T h e o r y  t o S o l i d S t a t e P r o t o n NMR  75  5.2.1  L i n e - S h a p e s o f S o l i d S t a t e PMR S p e c t r a  5.2.2  Relaxation  .  .  75 77  5.3  Experimental  86  5.4  Results  87  5.5  5.6  6.  Poly(ether  5.4.1  Line-Shape Results  87  5.4.2  Spin-Lattice Results  93  Discussion  101  5.5.1  Line-Shape Discussion  101  5.5.2  Spin-Lattice  Relaxation Discussion  . . . .  Summary a n d C o n c l u s i o n o f PMR Work  104  108  CONCLUSION  110  6.1  G e n e r a l Remarks  110  6.2  Summary  110  6.3  Suggestions  for  Continuation of  the Study  . . . .  113  Vll  REFERENCES  8.  APPENDICES  1  1  5  120  viii  L I S T OF TABLES  Page Tables  2.1  P h y s i c a l and M e c h a n i c a l P r o p e r t i e s  o f PEEK R e s i n  . . .  20  2.2  P h y s i c a l and M e c h a n i c a l P r o p e r t i e s  o f PPS R e s i n  . . .  22  3.1  DSC R e s u l t s  4.1  The S p e c t r a l A s s i g n m e n t  for  PEEK  4.2  The S p e c t r a l L i n e w i d t h s  for  Crystalline  for  PEEK a n d PPS  30  65  a n d Amorphous  PEEK 4.3  66  Optimum C o n t a c t Time R e s u l t s C r y s t a l l i n e PEEK  f o r Amorphous  5.1  Half Height Linewidths  5.2  Ti V a l u e s f o r  5.3  A c t i v a t i o n Energies  5.4  S p i n - L a t t i c e R e l a x a t i o n Times f o r Components o f PEEK  and 71  o f PMR S p e c t r a  87  PEEK a n d PPS  from Arrhenius  94  Plots  the  98  Individual 100  ix  L I S T OF FIGURES  Page Figures 2.1  Polycondensation reaction of acid chlorides  6  2.2  R e a c t i o n o f b i s f l u o r o p h e n y l k e t o n e and t h e b i s potassium s a l t of bis-4-hydroxyphenyl ketone . . . .  7  2.3  The p o l y m e r i z a t i o n r e a c t i o n o f  poly(phenylene  sulfide)  9  2.4  The r e p e a t i n g u n i t  o f PEEK  10  2.5  The c o n f o r m a t i o n o f t h e c r y s t a l l i n e  2.6  Stacked lamellae  12  2.7  Lamellar  13  2.8  (a) (b)  PEEK c h a i n  . . .  10  growth  Quenched s p h e r u l i t e s F u l l y grown s p h e r u l i t e s  ^  3.1  S e c t i o n a l v i e w o f DSC m e a s u r i n g c e l l  27  3.2  DSC s c a n s o f a m o r p h o u s a n d c r y s t a l l i n e  PEEK  29  3.3  DSC s c a n s o f a m o r p h o u s a n d c r y s t a l l i n e  PPS  30  3.4  S k e t c h o f a DSC g l a s s  3.5  DSC g l a s s PEEK  t r a n s i t i o n curve  t r a n s i t i o n curve f o r  31  annealed  amorphous 32  3.6  DSC c r y s t a l l i z a t i o n  4.1  The i n t e r a c t i o n o f  exotherm f o r  a m o r p h o u s PEEK  two d i p o l a r n u c l e i  . . .  34  i n a magnetic  field  42  4.2  The e f f e c t  of chemical s h i f t  4.3  The c r o s s - p o l a r i z a t i o n  anisotropy  experiment  interaction  .  44 48  X  4.4  The t i m e a v e r a g e d r e s u l t  of a vector  spinning  about  an a x i s  51  4.5  The d i p o l a r  d e p h a s i n g p u l s e sequence  53  4.6  The CP/MAS s p e c t r u m o f c r y s t a l l i n e  4.7  The d i p o l a r  4.8  The CP/MAS s p e c t r a o f PPS, v a r y i n g c r y s t a l l i n i t i e s  4.9  The CP/MAS s p e c t r u m o f c r y s t a l l i n e  4.10  The d i p o l a r  4.11  The CP/MAS s p e c t r a o f a m o r p h o u s a n d  PPS  57  dephased spectrum o f c r y s t a l l i n e  PPS  .  .  58  .  .  59  PEEK  62  dephased spectrum o f c r y s t a l l i n e  PEEK  .  .  crystalline  PEEK  66  4.12  The v a r i a b l e  4.13  Variable  contact  time p l o t s  for  a m o r p h o u s PEEK  4.14  Variable contact c a r b o n o f PEEK  time p l o t s  for  a non-protonated  contact  t i m e s p e c t r a o f PEEK  67 . . .  The i n v e r s i o n r e c o v e r y T ^ e x p e r i m e n t  5.2  The s p i n - s p i n r e l a x a t i o n e f f e c t  5.3  T2,  5.4  The d e p e n d e n c e o f r e l a x a t i o n t i m e s o n t e m p e r a t u r e  5.5  The d e p e n d e n c e o f  t h e FID a t  inverse  1/e  of  .  80 82  the o r i g i n a l value  83  the l o g o f r e l a x a t i o n times  .  temperature  84  85  PMR s p e c t r a o f PEEK a n d PPS a t a m b i e n t t e m p e r a t u r e  5.7  L i n e w i d t h vs temperature f o r c r y s t a l l i n e PEEK L i n e w i d t h vs temperature f o r a m o r p h o u s PEEK  spectra  of  spectra  of  L i n e w i d t h vs temperature c r y s t a l l i n e PPS  for  spectra  L i n e w i d t h vs temperature a m o r p h o u s PPS  for  5.10  .  on  5.6  5.9  69  70  5.1  5.8  63  .  .  88  89 90 of 90 spectra  of 91  xi  5 11  PMR s p e c t r a f o r  5 12  Arrhenius p l o t  for  crystalline  5 13  Arrhenius p l o t  for  a m o r p h o u s PEEK r e l a x a t i o n  5 14  Arrhenius p l o t  for  crystalline  5 15  Arrhenius p l o t  for  a m o r p h o u s PPS r e l a x a t i o n  5 16  A partially  5 17  The T ^ t e m p e r a t u r e p r o f i l e  PEEK a n d PPS a t h i g h  temperature  PEEK r e l a x a t i o n  PPS r e l a x a t i o n  relaxed spectrum o f c r y s t a l l i n e o f benzene  PPS  92 .  .  95  .  .  .  95  .  .  .  96  .  .  .  97  .  .  98 .  106  xii  ACKNOWLEDGEMENTS  Sincere  thanks are expressed t o Dr.  a n d e n c o u r a g e m e n t d u r i n g my c o u r s e a t I Dr.  Herring for his  fellows  o f our research  J a g a n n a t h a n f o r much h e l p a n d g u i d a n c e a n d t o D r .  f o r many k i n d n e s s e s  and a s s i s t a n c e  support  U.B.C.  am i n d e b t e d t o t h e p o s t d o c t o r a l  N.R.  F.G.  i n the p r e p a r a t i o n o f  group:  J.M.  Willis  this  manu-  J.  Rendell  script. Special all A.L.  their  t h a n k s a r e due t o M r .  patient  MacKay f o r I  shops,  and p r a c t i c a l h e l p .  several  invaluable  am v e r y a p p r e c i a t i v e in particular  Finally,  Columbia i s  of  support  I would also l i k e  to thank  for  Dr.  discussions.  K.  the e l e c t r i c a l  Sukul and Mr.  from the Natural  (NSERC), P o l y s a r L t d .  gratefully  D e l i k a t n y and Mr.  the work o f  I m e n t i o n Mr.  financial  Research C o u n c i l  E.J.  acknowledged.  E.  and m e c h a n i c a l  Matter.  Science and  and t h e U n i v e r s i t y  of  Engineering British  1-  1.  1.1  INTRODUCTION  GENERAL INTRODUCTION  Poly(ether (PPS),  (PEEK), and p o l y ( p h e n y l e n e  a r e two s e m i - c r y s t a l l i n e  industrial resins  ether ketone),  interest.  These t h e r m o p l a s t i c s  as t h e m a t r i x m a t e r i a l s  importance  setting resins, fibre  to  the composite  However,  for  industry.  (1)  far  fabrication  from the m i l i t a r y  is  of  thermofor  performance  techniques the  are  impetus  aviation  i n the a p p l i c a t i o n and d e v e l o p -  the metal a l l o y s  (APC-1) b o a s t o f  overcome b y t h e r m o p l a s t i c s ,  it  and i n  of  2  structural  strength-to-weight  The m a n u f a c t u r e r s  b e i n g 30% l i g h t e r  1670 MN m "  disadvantages  aging w i t h fatigue.  The  recent years,  i s b e i n g t h r e a t e n e d . Much o f  exceed the a l l o y s .  and h a v i n g a s t r e n g t h o f Significant  Until  s t r e n g t h and toughness p r o p e r t i e s  the composites  PEEK/carbon f i b r e  composites.  materials.  composites v i e w i t h those o f ratio,  thermosetting  were the e x c l u s i v e m a t r i c e s  i n d u s t r y w h i c h has l o n g been a p i o n e e r  The s t i f f n e s s ,  considerable  advanced composite a p p l i c a t i o n s  composite research i s  m e n t o f new c o m p o s i t e  are r e p l a c i n g  a n d as s u i t a b l e  the thermoset market  thermoplastic  of  as t h e a d v a n t a g e s o f c e r t a i n h i g h  t h e r m o p l a s t i c s become e v i d e n t developed,  for  mainly the epoxies,  composites.  polymers  f o r high-performance  introduction of thermoplastics major  thermoplastic  sulfide),  than  the  aluminum  (2).  of thermosetting resin matrices  especially  of  can be  i n the area o f processing  T h e r m o s e t p r o c e s s i n g i s messy a n d l a b o u r  and  intensive,  - 2 -  requiring  l a r g e volumes o f s o l v e n t and a u t o c l a v i n g w i t h l o n g and  ate cure cycles.  Because t h e r m o s e t c u r i n g i n v o l v e s  between t h e r e s i n and c r o s s l i n k i n g a g e n t , shelf  lives  process  and o f t e n r e q u i r e  required for  and p r e s s u r e s  are needed,  t h e p r e p r e g s have  refrigerated  a thermoplastic,  a chemical  storage.  thus,  the mould c y c l e  There  reaction  limited  i s no  although high  elabor-  curing  temperatures  i s v e r y s h o r t a n d no  solvents  are used. The t w o m a j o r a r e a s o f f a i l u r e w i t h e p o x y / f i b r e space a p p l i c a t i o n s compressive  strength  become b r i t t l e that  interlaminar  and, because t h e r e  i s n o t caused by d e l a m i n a t i o n  (3,5-7).  than t h e i r  a 'state-of-the-art'  stronger,  ( 9 ) . A t 120°C,  and a t  thermoplastic remelted for tive  180°C,  repair  t o be a b l e  t o reuse o f f - c u t s  I n the past, because o f stiffness are r a r e  thermoplastics  the d i f f i c u l t y  far better; some p l a s t i c  to show  have  flow,  fail-  matrices (8).  composite,  In  a  the the  a g e d PEEK c o m p o s i t e was 15%  (9).  One f u r t h e r  (10,11);  is it  that is  advantage o f the p l a s t i c s  economically  the c a n be  attrac-  (1). h a v e f a i l e d as c o m p o s i t e  matrices  i n f i n d i n g a polymer which had b o t h  at high temperatures  tend  they  The t h e r m o p l a s t i c  the thermosets  and r e m o u l d i n g  hot/wet  thermoset counterparts  the humidity  over  aero-  t i m e s as much w a t e r b y w e i g h t as  75% s t r o n g e r  composites  is  in  comparison t e s t s  epoxy/carbon f i b r e  epoxy composite absorbed over t h r e e PEEK s a m p l e  and poor  Various  composites w i t h s t a n d f a t i g u e  crack resistance  against  (3)  thermoset composites  by d e l a m i n a t i o n .  tend t o absorb l e s s water test  fracture  ( 4 ) . When f a t i g u e d ,  and f a i l  thermoplastic  superior ure  are  composites  and good c h e m i c a l r e s i s t a n c e .  i n exhibiting both properties.  adequate PEEK a n d  These t w o p o l y m e r s h a v e  the  PPS  - 3 -  highest  thermal  stabilities  of  today's  engineering p l a s t i c s ,  m a t e l y 50% a b o v e t h e c o m p e t i n g e p o x y r e s i n s t a n c e o f PEEK a n d PPS t o a g g r e s s i v e due t o t h e s e m i - c r y s t a l l i n e amorphous t h e r m o p l a s t i c tance  (8). Just  effect  to revolutionize it  plastics  is  chemical environments  nature of  the polymers.  industry,  the thermoplastics  the thermoset composite  be f u l l y  that  the mechanical p r o p e r t i e s  known i n o r d e r  the performance of  the  (9).  to set r e l i a b l e  chemical  potential  Before  this  of  thermo-  the  confidence  limits  of  the composites:  conditions  and f a t i g u e  tensile  and f l e x u r e  as f u n c t i o n s  and t h e r m a l h i s t o r y  of  and  tests,  f o c u s s e d on t h e m o r p h o l o g y and c r y s t a l resistance  choosing a n a l y t i c a l  course,  (3,5-8,10,14,16).  is  limited  structure  these thermoplastics  techniques.  of  for  research  PEEK a n d PPS, b o t h r e n o w n e d f o r  to the s o l i d s t a t e ,  analysis  of  these  pre-  This,  acid  appears  of  solvent  thermoplastics  t h e one e x c e p t i o n b e i n g a s t u d y o f  dissolved i n concentrated s u l f u r i c X-ray d i f f r a c t i o n  the analysis  The  becomes a p r o b l e m when  Conventional polymer  I n n e a r l y every case,  has  the neat r e s i n s .  t h e m a c r o m o l e c u l e may b e s t u d i e d i n s o l u t i o n .  is not possible  resistance.  of  stress  temperature,  Research on t h e p h y s i c a l polymer c h e m i s t r y o f these p l a s t i c s  supposes t h a t  for  material.  shear s t r e n g t h ,  good s o l v e n t  can  t h e r e s e a r c h w h i c h h a s b e e n done a l r e a d y o n PEEK a n d  physical properties  environmental  resis-  significant  PPS h a s b e e n c o n c e r n e d w i t h t h e e v a l u a t i o n , o f v a r i o u s m e c h a n i c a l  cracking,  is  no  a l s o have the  industry  resis-  (9,13-15)  To d a t e ,  e v a l u a t e d h a s shown s a t i s f a c t o r y  essential  The b u l k o f  The o u t s t a n d i n g  as t h e t h e r m o s e t t i n g c o m p o s i t e s h a v e h a d a  on t h e m e t a l  happen,  (12).  approxi-  PEEK  (17). t o be t h e p r o m i n e n t  research  - 4 technique  for  these m a t e r i a l s  structure  of both polymers,  o f v a r i o u s polymer  (16,18-23).  as w e l l  samples.  Some d i f f e r e n t i a l  i n f r a r e d spectroscopy  (28,29)  r e s u l t s have a l s o been p u b l i s h e d .  (16,27)  resonance  t h e s t u d y o f PEEK a n d PPS f o r , the very  important  solved into  and t h e m o l e c u l a r m o t i o n o f  a l s o an a t t r a c t i v e  the polymer NMR g i v e s  intractible  insight  a n d PPS b y t h i s m e t h o d . plastics (i)  (ii)  are found i n the current  this  Whitaker  and coworkers  resolution (iii)  (32)  by b r o a d - l i n e ,  spin-lattice  a proton  thermo-  poly(ether decoupled  acid.  The  analy-  press.  (24) p u b l i s h e d a s o l i d s t a t e ,  spectrum o f  S c h l i c k a n d McGarvey sulfide)  in  structure  s t u d y o f PEEK  study of a  the polymer d i s s o l v e d i n s u l f u r i c  spectrum i s  dis-  literature:  i n strong acids which includes  of  has  polymer  o f NMR w o r k o n t h e s e  ether ketone)  sis  the  research of  ( 1 7 ) h a v e done a s o l u b i l i t y  spectrum of  into  in  p o l y m e r s w h i c h c a n n o t be had b y  Karasz e t a l .  l^C  the technique  t o d a t e t h e r e has been l i t t l e  Three r e p o r t s  (8,  technique  sample need n o t be  any o t h e r method. There has been c o n s i d e r a b l e s y s t e m s u s i n g NMR ( 3 0 ) b u t  estimates  spectroscopy  l i k e X-ray d i f f r a c t i o n ,  analysis.  crystal  scanning c a l o r i m e t r y  and m e c h a n i c a l  (NMR) i s  advantage t h a t  solution for  has y i e l d e d t h e  as p e r c e n t c r y s t a l l i n i t y  24-26),  Nuclear magnetic  It  high-  PEEK. s t u d i e d the dynamics o f  p r o t o n magnetic  resonance,  poly(phenylene determining  r e l a x a t i o n t i m e s a n d s e c o n d moments as f u n c t i o n s  of  temperature. The w o r k i n t h i s  thesis  and h i g h r e s o l u t i o n ,  i s unique  in that  it  analyzes  spectra for both crystalline  broad-line,  and amorphous  -  5  -  s a m p l e s o f PEEK a n d PPS.  1.2  THE ORGANIZATION OF THE THESIS  Chapter  2 discusses  two t h e r m o p l a s t i c s  the h i s t o r y ,  s t u d y o f PEEK a n d PPS:  (i)  s o l i d s t a t e NMR, a n d ( i i i )  thermal analysis,  high resolution,  broad-line  3  plastics  p r o t o n magnetic  the m a t e r i a l s .  as f u n c t i o n s  of  to  resonance.  the 1 3  s p e c t r o s c o p y and i t s  application proton  C  Chapter  Chapter 4 focusses  5 d e a l s w i t h t h e use o f b r o a d - l i n e  The s i x t h a n d f i n a l  project.  of  (ii)  t o examine t h e morphology and m o l e c u l a r m o t i o n s  i n the thesis  the  techniques  high resolution ^ C solid state  resonance  of  applied three d i s t i n c t  the thermal analysis  a n d PPS. C h a p t e r  and p r o p e r t i e s  studied.  This research project  3 presents  synthesis  on  t o PEEK  magnetic of  the  temperature. chapter  s e r v e s t o summarize t h e w o r k  a n d makes s u g g e s t i o n s  for  the c o n t i n u a t i o n o f  presented  this  - 6 2.  2.1  HISTORY AND  2.1.1  MATERIALS  SYNTHESIS  Poly(ether ether ketone)  In the 1960's, researchers of three major p l a s t i c s companies reported the synthesis of polyetherketones:  ( i ) Bonner of du Pont, ( i i )  Goodman et a l . of ICI and ( i i i ) Farnham et a l . of Union Carbide Bonner and Goodman performed a polycondensation (Figure 2.1)  (33).  of a c i d chlorides  and Farnham et a l . reacted bis-4-fluorophenyl ketone  the potassium s a l t of bis-1-hydroxyphenylketone i n sulpholane 2.2). The p r i n c i p a l problem i n the synthesis was once formed, the polymer was  with  (Figure  that of solvent, for,  insoluble i n most organic solvents.  As a  r e s u l t , a polymer of high molecular weight could not be obtained. This d i f f i c u l t y was  l a t e r solved, i n one case by using l i q u i d HF as the  solvent and i n a another by carrying out the reaction i n a r y l sulfones at 280-340°C, j u s t below the melting point of the polyetherketone  C^o^C^coci N  —'  N  —'  AICI in CH CI at 20°C 3  2  2  ~®-co-®-oFigure 2.1:  Polycondensation  (33).  reaction of acid chlorides.  n  - 7 -  F-@-CO-@-F  +  KO-@>-COH^OK ~230°C  in sulpholane  --©-co-0-0n Figure 2.2:  Reaction of bisfluorophenyl ketone and the b i s potassium s a l t of bis-4-hydroxyphenyl ketone.  Because o f i t s e x c e l l e n t initial  development  applications. for  light  chemical and e n v i r o n m e n t a l  o f c o m m e r c i a l PEEK was d i r e c t e d t o w a r d s w i r e  I t was d u r i n g t h i s w o r k t h a t  weight  resistance, the  structural  the great potential  c o m p o s i t e s was r e c o g n i z e d .  o f forms.  The n e a t  thermoplastic  amorphous f i l m a n d i n s e m i - c r y s t a l l i n e posites,  A P C - 1 a n d APC-2  as r e i n f o r c e m e n t ; consolidated  resin  o f PEEK  I n 1981 I C I  i n t r o d u c e d PEEK t o t h e m a r k e t u n d e r t h e t r a d e name o f V i c t r e x , in a variety  available  i s s o l d as a n  powder o r p e l l e t s .  (aromatic polymer composite)  The PEEK com-  use carbon  t h e y a r e o b t a i n e d as p r e p r e g t a p e a n d f i l a m e n t ,  sheets.  coating  fibre a n d as  - 8 -  2.1.2  Poly(phenylene s u l f i d e )  Poly(phenylene ketone). Crafts  In fact,  sulfide)  significantly  predates poly(ether  ether  as e a r l y as 1888 t h e r e was a r e p o r t b y F r i e d e l  o f a c e r t a i n r e a c t i o n b y - p r o d u c t w h i c h i s now t h o u g h t  and  t o b e PPS  ( 1 5 ) . I n 1898 G r e n v r e s s e r e c o r d e d f o r m a t i o n o f a n i n s o l u b l e  r e s i n by the  r e a c t i o n o f benzene w i t h s u l f u r  chloride  i n the presence o f aluminum  ( 1 6 ) . T h e r e was n o f u r t h e r p r o g r e s s u n t i l Ontario,  published  Sulfide Resins"  "A D r y S y n t h e s i s  physical  synthesis proposed by Macallum,  consistent  o f Aromatic  Phenylene  (31). This  author  s t r e n g t h o f some o f t h e r e s i n s .  though i n t e r e s t i n g ,  The  was o f n o u s e  because t h e r e a c t i o n c o u l d n o t be c o n t r o l l e d  to obtain a  product.  I n 1967 Edmonds a n d H i l l poly(phenylene  sulfide)  w i t h sodium s u l f i d e substitution,  patented,  f o r the P h i l l i p s  synthesis process which reacts  in a polar  organic  solvent.  w i t h N a C l f o r m e d as a b y - p r o d u c t .  Six years  later,  i n 1973 P h i l l i p s  product w i t h a slogan:  "Ryton,  R y t o n i s made f o r t w o d i f f e r e n t the general mid-performance m e t a l s where a l i g h t e r , required.  the p l a s t i c markets.  composites.  Company,  a  p-dichlorobenzene  There i s a n u c l e o p h i l i c (See F i g u r e  2.3)  b e g a n p r o d u c i n g PPS c o m m e r c i a l l y ,  u s i n g t h e t r a d e name o f " R y t o n " . The P h i l l i p s  is  Sulfides:  i n the Journal o f Organic Chemistry  noted the " s a t i s f a c t o r y "  industrially  1948 when M a c a l l u m i n L o n d o n ,  brochures promote  that  thinks  i t ' s a metal".  The p r i m a r y m a r k e t PPS c o m p o s i t e s  c h e a p e r o r more e n v i r o n m e n t a l l y  the  are  is  that  replacing  resistant  part  The s e c o n d a r y m a r k e t i s i n e l e c t r i c a l m a t e r i a l s w h e r e  c o m b i n a t i o n o f good o v e r a l l  insulative  properties,  of  flame r e s i s t a n c e  the and  - 9 -  CI  CI  SNa  solvent  ;  SNa •  Na  CI  CI  CI  CI n Figure 2.3:  The  polymerization reaction of poly(phenylene  t h e r m a l s t a b i l i t y make PPS  sulfide).  a e x c e l l e n t choice f o r wire coatings  and  e n c a p s u l a t i o n ( 1 5 ) . PEEK i s a l s o u s e d i n s i m i l i a r e l e c t r i c a l a p p l i c a tions .  2.2  MORPHOLOGY AND  2.2.1  Poly(ether ether ketone)  The  PROPERTIES  r e p e a t i n g u n i t of p o l y ( e t h e r ether ketone) i s comprised of  t h r e e a r y l groups j o i n e d by e t h e r and ketone l i n k a g e s , w i t h an e t h e r - t o k e t o n e r a t i o o f 2:1. The  (See F i g u r e  2.4).  c o m m e r c i a l polymer i s r e p o r t e d as h a v i n g w e i g h t average mole-  c u l a r w e i g h t s r a n g i n g from 2 . 0 x l 0  4  to 3 . 9 x l 0  4  g mol"  1  (17,34).  - 10 -  0  Figure 2 . 4 :  Peek i s  The r e p e a t i n g u n i t  of poly(ether  a semi-crystalline  polymer.  n  ether  ketone)  The c r y s t a l  s t r u c t u r e has  d e t e r m i n e d by X - r a y s c a t t e r i n g and i s p r e s e n t e d and d i s c u s s e d i n literature yields  (18,19,20,21,23,35).  an e s t i m a t e  The l a t t i c e poly(phenylene able  in  the  of  lattice  t h e two t y p e s o f  the percent  crystallinity  s t r u c t u r e was f i r s t  oxide),  orthorhombic u n i t  The X - r a y d i f f r a c t i o n of  the  technique  (18).  t h o u g h t t o be i d e n t i c a l  l i n k i n g groups p r e s e n t  (20).  structure  '«  Figure 2.5  Figure  2.5:  *!  The c o n f o r m a t i o n o f  the c r y s t a l l i n e  that  proposed  shows  i i  10.0 A  to  to account  124°  i i  also  of  indistinguish-  Subsequent work c o n f i r m e d t h e  c e l l but modified the c e l l  the  sample.  t h e e t h e r and k e t o n e groups b e i n g  cell  been  PEEK c h a i n .  the  for  - 11 -  conformation of  the c r y s t a l l i z e d chain.  k e t o n e and e t h e r  links  of-plane  (20,36).  tilting  is  The c r y s t a l l i n i t y crystalline.  l i n e phase. data  ( 2 3 , 3 5 ) b u t on t h e i r  crystalline.  a m o r p h o u s t o a b o u t 40% X-ray  peaks d i v i d e d by t h e t o t a l  scan y i e l d s  own, appear  out-  the f r a c t i o n of  insufficient  for  area  crystal-  support reliable  estimates. p o l y m e r has two d i s t i n c t  The c h a i n s o f  i n a completely  random f a s h i o n .  Rodriguez  to a bucketful  strength of  this  analogy l i e s  "worms" b u t  also  i n t h e i r motion,  important  consideration  addition,  it  is  for  of crystalline  popular  and i s  this  o f v e r y l o n g t h i n worms.  The  of  is  as t h e  as t h e b u c k e t phase i s  dictates  the f o r m a t i o n of  These l a m e l l a e is  that just  frequency  is  the  considerably  an o r d e r e d lamellae  are stacked,  i l l u s t r a t e d by the simple  the an In and  squirm-  heated. more  a question of greater uncertainty  of c r y s t a l l i n e  theory  material.  amorphous r e g i o n s ;  com-  increases w i t h temperature,  the c r y s t a l l i n e  The d e f i n i t i o n  The c u r r e n t l y  (37) humorously b u t a p t l y  segmental Brownian motion i s  t h e worms becomes more v i g o r o u s  and  coiled  i n the e x p l a n a t i o n o f polymer p r o p e r t i e s .  degree o f m o t i o n i n the polymer  to describe  amorphous  n o t o n l y i n t h e random p o s i t i o n s  an a p p r o p r i a t e p a r a l l e l  The m o r p h o l o g y o f  phases:  t h e amorphous phase a r e i n d i s o r d e r ,  t h e amorphous p o l y m e r  debate.  the  show some  i s u s u a l l y assessed by w i d e - a n g l e  the d i f f r a c t o m e t e r  A semi-crystalline  difficult  likely  D e n s i t y and i n f r a r e d r e f l e c t i o n have been used t o  crystallinity  ing of  from f u l l y  the area of the c r y s t a l l i n e  i n t e g r a t e d under  pares  and t h e a r y l r i n g s  o f PEEK v a r i e s  Crystallinity  scattering;  X-ray  124°,  The a v e r a g e b o n d a n g l e f o r  and  structure. or  platelets  separated by schematic  diagram  - 12 of Figure  2.6.  CRYSTALLINE  Figure 2.6:  Stacked lamellae showing c r y s t a l l i n e (38).  and amorphous regions  I t i s now assumed t h a t t h e r e i s c h a i n f o l d i n g i n the l a m e l l a e , although  the e v i d e n c e f o r t h i s i s n o t c o n c l u s i v e . The f o l d i n g i s n o t  t h o u g h t t o be a b s o l u t e l y r e g u l a r : a m o l e c u l e may  l e a v e a l a m e l l a and r e -  e n t e r a t a d i f f e r e n t l o c a t i o n o r c o i l randomly i n t h e amorphous phase. The l a m e l l a r t h i c k n e s s depends upon the t e m p e r a t u r e a t w h i c h c r y s t a l l i z a t i o n o c c u r s . B l u n d e l l and Osborn have e s t i m a t e d l a m e l l a r t h i c k n e s s e s o f PEEK from s m a l l - a n g l e X-ray s c a t t e r i n g d a t a and show t h a t the t h i c k ness i n c r e a s e s from 20 A t o 59 A w i t h v a r i a t i o n o f t h e c r y s t a l l i z a t i o n t e m p e r a t u r e from 200°C t o 320°C ( 3 5 ) . The l a m e l l a r f o r m a t i o n b e g i n s a t a n u c l e a t i o n s i t e and branches r a d i a l l y outward u n t i l the g r o w i n g edge meets the boundary o f a n o t h e r c r y s t a l l i z i n g r e g i o n o r u n t i l the m a t e r i a l i s quenched.  (See F i g u r e 2.7.)  These l a r g e r c r y s t a l l i n e s t r u c t u r e s a r e  - 13 -  called spherulites. or,  i f one meets t h e o t h e r ,  chains this  T h e y may b e c i r c u l a r  are tangential  polygonal  or spherical  [Figure  2.8(b)).  to the growth d i r e c t i o n ;  [Figure  2.8(a)],  The p o l y m e r  an attempt  to  illustrate  i s made i n F i g u r e 2 . 7 .  a Figure 2 . 7 :  (a) (b)  Lamellar growth, r a d i a l l y outward, Growing f i b r i l t i p ( 3 9 ) .  Figure 2 . 8 :  (a) (b)  Quenched spherulites. Boundaries formed where spherulites meet ( 3 9 ) .  Spherulites scopy.  Blundell  spherulites  o f t e n grow l a r g e  enough t o be obseved b y o p t i c a l  a n d O s b o r n i n a s t u d y o f PEEK m o r p h o l o g y  of radii  13 t o 22 pm. The l a r g e r  micro-  (35) report  a r e f o u n d i n t h e samples  - 14 -  annealed at higher polarized light, The t w i s t  temperatures.  exhibit  of  These s p h e r u l i t e s ,  the c h a r a c t e r i s t i c  the r i b b o n - l i k e  n u c l e u s causes a l t e r n a t e  constructive  the t r a n s m i t t e d p o l a r i z e d l i g h t . birefringence  fibrils  lists  the three  tion,  crystallization  important  engineering resins  (12),  reports  polarity  j o i n e d by ether  or ketone linkages,  to maintain r i g i d i t y  are a t  the  top  i n the repeating u n i t the rings provide  i n the macromolecular  PEEK h a s a r e l a t i v e l y  335°C.  and Van d e r Waals f o r c e s  The t h e r m a l s t a b i l i t y  become d e g r a d e d b y c h a i n s c i s s o n o r a i r  is  that  oxidation at  is  due t o  of aryl the  are the  rings  necessary  c h a i n . A second the polymer the h i g h  not  processing  narrow p r o c e s s i n g range o f  360°C  the onset o f  in  to  (40). The g l a s s  transition  amorphous phase o f (T„),  on  Temperature  extraordinarily high,  t o be c o n s i d e r e d i n t h e r m a l s t a b i l i t y  temperatures.  transi-  i n a r e c e n t paper Laboratory  20)  220°C.  such a h i g h v a l u e . the polymer;  the  T a b l e 2 . 1 , (page  Polyetheretherketones  of  400°C  of  positive  o f PEEK: g l a s s  Woodhams,  the Underwriters  aromatic nature  factor  transitions  o f PEEK i s  Strong i n t e r c h a i n a t t r a c t i o n s ,  stiffness  interference  show a  the m a t e r i a l .  and m e l t i n g p o i n t .  w i t h a UL r a t i n g o f  for  of  temperature  The m e l t i n g t e m p e r a t u r e  responsible  and d e s t r u c t i v e  the  n a t u r e o f PEEK h a s s i g n i f i c a n t b e a r i n g o n  19 c o m m e r c i a l p l a s t i c s .  the l i s t ,  pattern.  as t h e y g r o w away f r o m  PEEK s p h e r u l i t e s  p h y s i c a l and mechanical p r o p e r t i e s  of  Maltese cross  (35).  The s e m i - c r y s t a l l i n e  Index f o r  when v i e w e d b y  indicates  the polymer.  Below t h e g l a s s  free  rotation  transition  t h e p o l y m e r c h a i n s e g m e n t s do n o t h a v e s u f f i c i e n t  the  temperature  e n e r g y t o move  - 15 -  p a s t each o t h e r . to allow for glass  A c e r t a i n amount o f e n e r g y i s n e e d e d t o c r e a t e  t h e r o t a t i o n o r d i f f u s i o n o f t h e p o l y m e r c h a i n . As  transition  barrier  temperature  is  become more f r e q u e n t .  instantaneous,  t h e jumps o v e r  Because t h e s e m o l e c u l a r  t h e new e q u i l i b r i u m  r e l a x a t i o n time of  temperature  approached,  the molecular  Quite d i f f e r e n t phase t r a n s i t i o n ,  the molecule.  is  reached;  is  transition  is  thermodynamic v a r i a b l e s .  tive  the Gibbs f r e e  of  heat capacity  exhibits  not  increment the  transition  which i s  a first  a second o r d e r  For example,  energy w i t h respect  are  time is  the p a r t i a l  to temperature  an a b r u p t change a t t h e g l a s s  order  transition  c h a r a c t e r i z e d b y an a b r u p t change i n t h e second d e r i v a t i v e primary  rotation  unhindered.  from the m e l t i n g p o i n t ,  the glass  this  Above t h e g l a s s  chain r o t a t i o n  the  an  'hole'  the  rotations  a c e r t a i n p e r i o d o f t i m e must e l a p s e a f t e r  i n temperature before natural  a  of  the  second d e r i v a shows  that  transition  temperature. It  is  important  to note t h a t  the glass  transition  temperature  dependent upon the o b s e r v a t i o n frequency used i n the experiment. m e a s u r e m e n t made b y t h e r m a l a n a l y s i s i n dynamic m e c h a n i c a l or d i e l e c t r i c period which is troscopy, transition  critical  a higher  (41).  is  a function of  spectroscopy,  For example,  it  the  gives  t i o n temperature  energy d i s s i p a t e d against  time to r e l a x .  increasing temperature.  the mechanical  loss  oscillation  a higher  t e m p e r a t u r e b e c a u s e when p e r t u r b e d a t a f a s t e r  a t i o n time decreases w i t h  rate;  i n dynamic m e c h a n i c a l  frequency of the o s c i l l a t i o n s  t a n g l e d polymer m o l e c u l e s have l e s s  A  the heating is  rate  At the glass  spec-  apparent the  The m o l e c u l a r  relax-  transi-  ( o f t e n e x p r e s s e d as t h e r a t i o  the energy s t o r e d i n the sample,  is  t a n 5)  of of  the  - 16 -  stressed polymer ing the e f f e c t stress  is  is  of  at  the stress  The g l a s s  uncoiling of  minimizing the a b i l i t y analogous manner,  practical  it  higher ether  considerthe  intermolecular  of  the forces,  I n a somewhat  a function of  the  frequency tempera-  (30). is  a u s e f u l parameter  the temperature  for  at which the  the  poly-  where t h e m a t e r i a l changes f r o m t h e o f t h e PEEK c h a i n makes  of  the r e s u l t i n g polymer  data claims  considerably account of  thereby  that  increasing the chain  is  flexible.  less  80% o f  transition  its  the f i b r e  s t r e n g t h even t o  temperature  a r e many e m p i r i c a l  for  rules  (2);  this  is  approximately  ratio  is  2/3  true  200°C, on  transi-  i n the composite.  the estimation of glass  t u r e s . One w h i c h h o l d s r e m a r k a b l y r a t i o which is  reinforcement  stiff-  Provisional  t h e c r y s t a l l i n e p h a s e w h i c h does n o t u n d e r g o a g l a s s  t i o n and a l s o because o f  PEEK, t h i s  further  PEEK r e t a i n s  above t h e g l a s s  the polymer.  rotation  t r a n s i t i o n t e m p e r a t u r e may b e made b y r e d u c i n g t h e p r o p o r t i o n i n the chain,  of  glassy  of  n e s s . However,  t h e h i g h Tg (144°C)  most  A polymer  linkages  product  field  The s t i f f n e s s  and e x p l a i n s  at which  t r a n s i t i o n appears a t h i g h e r  indicates  are a l t e r e d ,  the rubbery s t a t e .  difficult  the unique p o i n t  t r a n s i t i o n temperature  meric properties to  is  o f the system t o s t o r e energy.  The g l a s s  of reasons;  explained by  and above t h e T g , b y u n c o i l i n g  i s hindered by the  i n a stronger magnetic The g l a s s  is  system: below the Tg,  t h e Tg m e a s u r e d b y NMR i s  the spectrometer.  tures  transition  the molecules  This  on t h e polymer  s t o r e d by bond d i s t o r t i o n s  the chains.  of  t h e maximum ( 3 7 ) .  transition  i n many c a s e s i s  tempera-  the K e l v i n  f o r unsymmetrical polymeric  There  Tg/T  chains.  0.69.  The t h i r d t e m p e r a t u r e  t o be d i s c u s s e d i n t h e c h a r a c t e r i z a t i o n  of  m  For  - 17 -  semi-crystalline  polymers  is  the c r y s t a l l i z a t i o n  temperature.  T .  mechanism and morphology o f c r y s t a l l i z a t i o n have a l r e a d y been earlier  in this  section.  d e f i n e d as t h a t  The c r y s t a l l i z a t i o n  temperature  temperature at which the c r y s t a l l i z a t i o n  mum. T h e o r e t i c a l l y ,  the c r y s t a l l i z a t i o n  temperature o f  is  s h o u l d b e t h e same as t h e m e l t i n g t e m p e r a t u r e  (T )  this  I n polymeric  is  ever, This  true  for  any s i m p l e o r g a n i c  crystallization supercooling  molecular  ture,  a large driving force  induce c r y s t a l l i z a t i o n . the molecules  in a crystal  conformation.  In industry temperature of material  is  conversely,  it  required, it  is  is  t o know t h e  substance; systems,  how-  point.  matrices.  the c r y s t a l l i n e  One o f  thermoplastics of  is  For example,  plastic  the f a b r i c a t e d  m  if  is  c  temperato  a n amorphous  it  which i s  the unique advantages that  (T -T )  long  crystallization  c a r e m u s t be t a k e n n o t t o h e a t  desired c r y s t a l l i n i t y .  line properties  that  too sluggish to allow the chains  m o u l d e d a m o r p h o u s p a r t may t h e n b e a n n e a l e d i n o r d e r  crystalline  maxi-  substance  Below t h e c r y s t a l l i z a t i o n  is very important  thermoplastic  if  is  i s necessary because the polymer c h a i n s have such  the motion o f  orient  for  loosely  does n o t o c c u r u n t i l w e l l b e l o w t h e m e l t i n g  r e l a x a t i o n times t h a t  required to  compound.  m  discussed  rate  any  The  c  above t h e T  required,  the  to develop  the  of  the  t h e end u s e r can t a i l o r  c  and  semithe  crystal-  item through the simple process  of  annealing. The d e n s i t i e s  o f amorphous and c r y s t a l l i n e  m~  kg m"  3  and 1,400  smaller  3  respectively  d e n s i t y because  it  (18).  has a g r e a t e r  ments a r e sometimes used t o e s t i m a t e  PEEK a r e r e p o r t e d as 1 , 2 6 5  The a m o r p h o u s s a m p l e h a s f r e e volume.  Density  kg  a  measure-  the f r a c t i o n o f c r y s t a l l i n i t y  of  a  - 18 -  sample.  The c r y s t a l l i n e  structure,  d e n s i t y must be c a l c u l a t e d f r o m t h e  determined by X - r a y c r y s t a l l o g r a p h y ;  can be measured Tensile  strength  the f a b r i c a t e d  limit. ing,  is  a w i d e l y quoted parameter  failure fiber the  before  o t h e r modes o f  is  failure:  the y i e l d s t r e s s  tends  occurs  Fracture o f PEEK ( 8 ) . failure cross  toughness  section.  composites  cause  In addition,  the y i e l d stress  is  (34).  the c r y s t a l l i n e  is is  on  well  with  report  t h e amorphous and 90±1  The c r y s t a l l i n e to  for  a useful  Kemmish a n d Hay  phase o f  the  improve the s t r e n g t h o f sample i s  smaller  the  (38).  The  regions  PEEK r e t a i n s m o s t  s t r e n g t h does d r o p above T g ;  180°C,  and i s u s u a l l y  crack-  often contingent  Although at high temperatures  Toughness  stress  i n t h e amorphous and t h e n t h e c r y s t a l l i n e  the t e n s i l e  150°C t o  is  t e a r and f a t i g u e .  sample  The e l o n g a t i o n o f  of  Nevertheless,  t o a c t as a r e i n f o r c e m e n t  begin to break apart.  increase  reached.  o f PEEK r e s i n as 5 9 ± 1 MPa f o r  polymer  stiffness,  is  PEEK, t h e f a i l u r e  impact,  a 32% c r y s t a l l i n e  extension f i r s t  tensile  a r o u t i n e measurement w h i c h c o r r e l a t e s  MPa f o r  material.  the  of  applica-  i n v o l v e d s u c h as f a t i g u e ,  strength l i m i t  like  s t r e n g t h modulus. it  factors  at  and damaging e n v i r o n m e n t s w h i c h  the u l t i m a t e  composite matrices  fiber  material  i n the assessment  although i n p r a c t i c a l  item almost never y i e l d s  concentrations,  parameter because  its  of polymers,  There are always o t h e r  stress  t h e amorphous  directly.  the mechanical p r o p e r t i e s tions  crystal  in a  of  temperature  t h e s t r e n g t h d r o p s b y 64% ( 4 2 ) . one o f t h e p a r t i c u l a r l y  a measure o f  due t o a d i f f e r e n t  features  t h e e n e r g y a b s o r b e d on i m p a c t  e x p r e s s e d as e n e r g y p e r u n i t  PEEK c o m p o s i t e s  outstanding  a r e much t o u g h e r mode o f f a i l u r e .  area of  the  crack  than corresponding T a b l e 2 . 1 shows  at  the  epoxy  - 19 -  results point  of  the recent  Charpy t e s t  s t u d y o f Kemmich a n d Hay w h i c h e m p l o y s t h e  to determine  varying crystallinity.  the f r a c t u r e  t o u g h n e s s o f PEEK s a m p l e s  U n a g e d , a m o r p h o u s PEEK i s many t i m e s t o u g h e r  the c r y s t a l l i n e  f o r m . The amorphous shows a d u c t i l e  the c r y s t a l l i n e  exhibits  teristics,  crystallinity  trade-off  a brittle  failure.  s h o u l d be k e p t  low.  The i d e a l c r y s t a l l i n i t y  of  than  f a i l u r e mode w h i l e  For good toughness Unfortunately  because samples o f l o w c r y s t a l l i n i t y  solvent attack.  three  charac-  there  is  a r e most v u l n e r a b l e  a to  depends upon t h e end use o f  the  plastic. Solvent remarkably tests  resistance  impervious  are o f primary  a t room t e m p e r a t u r e , conditions  of  the c r y s t a l l i n e  to nearly a l l importance:  s a m p l e s show PEEK t o  aggressive  after  environments.  properties solvents: stripper kerosene, of  its  solvent  tests  show no s i g n i f i c a n t  o f PEEK c o m p o s i t e s a f t e r Genklene,  acetone,  (Ardox 2526) . A f t e r or  synthetic  original  of  the  effect  methyl e t h y l ketone, one m o n t h o f  quite  l o w e r i n g t h e Tg a n d material. i n the  mechanical  immersion i n a wide v a r i e t y  lubrication oil,  strength  Table 2.1 presents ketone).  similiar  show u p t a k e s o f 0.05% t o 0.2% ( 1 0 ) . W a t e r a b s o r p t i o n i s  reducing the elevated temperature p r o p e r t i e s  aging  humidity,  Epoxies under  u n d e s i r a b l e b e c a u s e t h e w a t e r a c t s as a p l a s t i c i z e r ,  Other  Humid  24 h r s a t 40% r e l a t i v e  PEEK a b s o r b s 0.14% m o i s t u r e .  be  of  c y c l o h e x a n e and  immersion i n h y d r a u l i c  the composite s t i l l  paintfluid,  r e t a i n e d 95%  (9). a summary o f  the p r o p e r t i e s  of poly(ether  ether  - 20 Table 2.1:  Physical and Mechanical Properties of PEEK Resin  -^©-o-@-o-®-c--  Chemical structure  o. melting point  340°C  613K  Tg glass t r a n s i t i o n  144 °C  417K< )  T  173°C  446K  T  m  c  crystallization  density:  crystalline amorphous  1,400 kg n T 1,265 kg m"  (18)  90 MPa 59 MPa  (34)  3 3  t e n s i l e strength^*) : fracture t o u g h n e s s ^ :  d  crystalline amorphous  c r y s t a l l i n e (30%) 3.0 kJ m" b r i t t l e f a i l u r e amorphous 85 kJ m"^ d u c t i l e f a i l u r e ( ^) 3  3  water absorption^ )  0.14%  0  (a)  s t r a i n rate 2 x 10"^ s,  (b)  charpy t e s t .  (c)  24 h, 40% humidity.  (d)  Table 3.1  2.2.2  Poly(phenylene  (10)  sulfide)  Most of the t h e o r e t i c a l aspects of the above section apply equally well to PPS as to PEEK. The structure of PPS i s somewhat simpler than that of PEEK; the repeating unit consists of a r y l groups linked by s u l f u r atoms. Light scattering studies indicate that the molecular weight of the v i r g i n r e s i n i s moderate, about 17,000 g mol"* (15). ever, when the powdered r e s i n i s heated i n a i r to temperatures  How-  ranging  - 21 -  f r o m 175 t o  280°C, a ' c u r i n g '  r e a c t i o n t a k e s p l a c e and t h r o u g h a combi-  nation of oxidation,  c r o s s - l i n k i n g and c h a i n e x t e n s i o n ,  weight  The c u r i n g p h e n o m e n o n ,  is  is  increased.  certainly  a n a d v a n t a g e as i t  the molecular weight of  the p l a s t i c  The maximum a t t a i n a b l e it  is  show t h a t ,  like  angles  in aliphatic  PEEK, t h e u n i t  t o each o t h e r  sulfur  polymers  PPS h a s somewhat l o w e r occurs a t about 282"C; 87°C;  and a g a i n ,  g  t h e r m i s maximum a t above t h e g l a s s  m  MPa f o r is  density  to  cell  is  X-ray  of  (16)  suggests  transition  orthorhombic,  o f the phenylene  ratio  temperatures  is  each  PEEK,  the c r y s t a l l i n e  polymer network.  are  110° j u s t  as  equals  2/3.  melting  approximately  The c r y s t a l l i z a t i o n  endo-  crystallizes  readily  temperature. is  quite  similar  t o PEEK, t h e c r y s t a l l i n e  regions  is  amorphous. a little  less  than that  o f PEEK,  the unannealed specimen ( 1 6 ) .  instead of having a r e i n f o r c i n g  The f r a c t u r e  However,  cell  groups  t h a n PEEK;  t r a n s i t i o n appears a t  a n d 47 MPa f o r  that  PEEK;  diffraction  the t r e n d normally observed i n s e m i - c r y s t a l l i n e  Brady  available.  applications.  o f PPS e x c e e d s t h a t  The p l a n e s  s t r e n g t h o f PPS i s  the annealed,  opposite  specific  (22).  a b o u t 8% more d e n s e t h a n t h e The t e n s i l e  controlling  122°C a n d t h e a m o r p h o u s p l a s t i c  transition  The m a t e r i a l  a simple method o f  and t h e s u l f u r bond a n g l e  the glass  the T / T  understood,  the v i r g i n r e s i n .  c o n t a i n i n g four-monomeric u n i t s . at r i g h t  for  molecular  though not w e l l  crystallinity  a b o u t 65%, o b t a i n e d f o r  studies  provides  the  o f PPS i n t r o d u c e toughness  i n an i n t e r l a m i n a r  for  interfacial  PPS r e s i n a l o n e  fracture  c o m p o s i t e s made w i t h PEEK, PPS, p o l y s u l f o n e  effect  test  of carbon  and epoxy m a t r i c e s ,  This  polymers. as  strain is  51  in in  the  not fibre t h e PPS  - 22 was only s l i g h t l y less tough than the PEEK and f a r superior to both other p l a s t i c s (4). PPS excels i n resistance to moisture uptake. Water absorption a f t e r 24 hours at room temperature was less than 0.02% of the i n i t i a l weight (10), much less than any of the other matrix thermoplastics. The environmental resistance of PPS i s an important s e l l i n g feature; PPS has excellent applications f o r pumps, valves and regulators which are i n contact with corrosive f l u i d s . Tests show PPS undamaged by any solvent at room temperature, although,  a f t e r extended exposure o f 6 months or  more at above Tg temperatures, some strong acids and organic solvents are capable o f damaging PPS (43). Table 2.2 presents a summary of the properties of poly(phenylene sulfide).  Table 2 . 2 :  Physical and Mechanical Properties of PPS Resin  Chemical structure T  m  282°C  melting point  Tg glass t r a n s i t i o n T  c  crystallization  density:  water absorption (24 h, ASTM D570) <> a  121°C  crystalline amorphous  t e n s i l e strength:  Table 3.1.  87°C  annealed unannealed  555K 360K< ) a  394K  1,430 kg m" 1,320 kg m"  3  3  < > 22  47 MPa 51 MPa  < >  <0.02%  (10)  16  - 23 -  2.3  THE MATERIALS USED I N THIS WORK  2.3.1  Poly(ether  ether  ketone)  Two f o r m s o f PEEK w e r e s t u d i e d , m a t e r i a l u s e d as " c r y s t a l l i n e " v i a Dr.  amorphous a n d c r y s t a l l i n e .  was o b t a i n e d f r o m I C I A m e r i c a s ,  G r e g Luoma o f D e f e n c e R e s e a r c h E s t a b l i s h m e n t  was i n t h e f o r m o f a l i g h t distribution  grey powder,  thickness. glass  as a t r a n s l u s c e n t ,  This  transition  it  brittle  a n d t u r n i n g opaque b e i g e  2.3.2  Poly(phenylene  The c r y s t a l l i n e Company,  It  flexible  f i l m of  Plastics,  3 mil  nominal  a m o r p h o u s . Upon h e a t i n g a b o v e  readily  crystallized,  b e c o m i n g more  colour.  PPS was m a n u f a c t u r e d b y t h e P h i l l i p s Luoma as a v e r y f i n e ,  was a v i r g i n r e s i n  from the r e a c t i o n solvent  Petroleum  f l o u r y powder  i n the form which i s  of  isolated  (15).  The a m o r p h o u s c o m p o s i t e m a t e r i a l was d o n a t e d b y A m e r i c a n T h e r m o plastics  Corporation,  a subsidiary  c o m p o s i t e was 40% g l a s s - f i l l e d , brown p e l l e t s  the  sulfide)  a g a i n s u p p l i e d by Dr.  pale beige colour. directly  amber,  in  size  (9).  f i l m was assumed f u l l y temperature,  It  The p o w d e r was  The a m o r p h o u s PEEK s a m p l e was p u r c h a s e d f r o m W e s t l a k e Pennsylvania,  Delaware,  (DREP).  w i t h a wide p a r t i c l e  ( a p p r o x i m a t e l y 0 . 0 1 t o 1 mm d i a m e t e r ) .  assumed t o b e a b o u t 35% c r y s t a l l i n e  Pacific  The  of Phillips  processed i n t o  h a v i n g an average d i a m e t e r  P e t r o l e u m Company. irregularly  of about  3 mm.  shaped,  The  - 24 -  III.  3.1  THERMAL ANALYSIS:  DIFFERENTIAL SCANNING CALORIMETRY  THERMAL ANALYSIS THEORY  Thermal a n a l y s i s has, ment o f  some m a t e r i a l  (44).  Differential  large  family  DSC i s  of  thermal a n a l y t i c a l  (DTA) t e c h n i q u e .  of  (DSC) i s j u s t  techniques.  DSC d i f f e r s  one m e t h o d i n  Thermal  1960s,  informathe  i n t e m p e r a t u r e between a sample and a r e f e r e n c e m a t e r i a l  to maintain i t  rate.  a t t h e same t e m p e r a t u r e  as t h e r e f e r e n c e .  that  high temperature  r e p l a c e d t h e DTA m e t h o d ,  mine g l a s s capacities,  The m o s t  the scanning  save p e r h a p s  sampl lau-  transicurves.  for  some  applications.  Polymer c h e m i s t s were q u i c k t o r e c o g n i z e science.  when  the  i n DSC t h e e n t h a l p y o f  c a n be o b t a i n e d d i r e c t l y by i n t e g r a t i o n o f  DSC h a s now g e n e r a l l y  dif-  On t h e o t h e r h a n d , DSC u s e s a s e r v o  o f h e a t w h i c h m u s t be a d d e d t o  d a b l e a d v a n t a g e o f DSC o v e r DTA i s  a  Analysis  i n t h e p a r a m e t e r m e a s u r e d . DTA r e c o r d s  system t o measure t h e q u a n t i t y  polymer  temperature"  f r o m DTA n o t so much i n t h e f i n a l  both are heated at a constant  polymer  measure  Developed i n the  t h e much o l d e r D i f f e r e n t i a l  t i o n gained but rather  tions  come t o mean " t h e  r e s p o n s e t o a programmed change o f  Scanning C a l o r i m e t r y  an o f f - s h o o t  ference  as a g e n e r a l t e r m ,  For n e a r l y  transitions,  two decades,  melting points,  thermal degradation,  t h e v a l u e o f DSC t o  DSC h a s b e e n e m p l o y e d t o crystallization  and m i s c i b i l i t i e s  kinetics,  o f many,  deter heat  varied  systems.  The s i g n a l  o b t a i n e d b y DSC i s p r o p o r t i o n a l  to  the d i f f e r e n c e  in  th  - 25 heat capacity of temperature  t h e sample and t h e r e f e r e n c e c e l l .  The g l a s s  i s marked b y a change i n t h e h e a t c a p a c i t y o f  a n d o n t h e DSC s c a n t h i s  a p p e a r s as a s u d d e n e n d o t h e r m i c  the  As t h e p o l y m e r u n d e r g o e s t h e c h a n g e f r o m a g l a s s  solution,  the  increase  i n the heat  is  The m e l t i n g p o i n t  (T ) It  i s p o s s i b l e because the o r d i n a t e the heating rate of  yields tion.  t h e DSC c e l l  converted into units  Generally  in units it  is  the  is  t h e same way as f o r  converts enthalpy.  to  at  is  in units  the u n i t s  is,  power.  o f power  (the units to  of  of  are  heat  temperature  the enthalpy o f  is  of  This  the  transi-  It  Is  t h e peak shape and p o s i t i o n a r e e f f e c t e d b y essentially  the  indepen-  t e m p e r a t u r e and e n t h a l p y a r e a r r i v e d a t  the melting t r a n s i t i o n .  t h e DSC s c a n i s t h e more s t a b l e  Again,  constant,  that  the  rate.  The c r y s t a l l i z a t i o n  temperature,  t h e DSC c u r v e  the curve w i t h respect  of energy,  for  the endothermic peak a r e a .  is  the  s i m p l e t o o b t a i n an e s t i m a t e  i n t e g r a t e d v a l u e o f t h e peaks  dent of the h e a t i n g  an  l a t e n t heat  e x p r e s s e d as J o u l e s p e r g r a m o f s a m p l e .  worth noting that while scanning r a t e ,  rubbery  t a k e n as t h e t e m p e r a t u r e  of energy-per-degree  The i n t e g r a t i o n o f  a value  of  additional  is  m  the m e l t i n g enthalpy by i n t e g r a t i o n o f  capacity).  the  i n d i c a t e d b y an e n d o t h e r m i c peak on  w h i c h t h e t h e p e a k maximum o c c u r s .  readily  to a  f r e e d o m above Tg causes  t h e DSC s c a n b e c a u s e t h e p o l y m e r r e q u i r e s  If  in  capacity.  The m e l t i n g t r a n s i t i o n  change o f p h a s e .  material  shift  baseline.  introduction of rotational  transition  the  crystallization  e x o t h e r m i c because t h e amorphous semi-crystalline  the c r y s t a l l i z a t i o n  maximum a n d a n e s t i m a t e  At  f o r m w h i c h has  temperature  of the c r y s t a l l i z a t i o n  i n much  is  polymer  lower  taken from the  enthalpy  i s made b y  peak  - 26 -  integration of  3.2  the peak  area.  PREVIOUS DSC WORK ON PEEK AND PPS  Other w o r k e r s have used D i f f e r e n t i a l study of poly(ether  ether ketone)  Kemmish a n d Hay ( 3 4 ) crystalline  found heat capacities  a l s o examined the e f f e c t  t r a n s i t i o n curve.  diffraction  and p o l y ( p h e n y l e n e of  Yoda ( 2 5 )  to study the e f f e c t s  melting temperatures  and p o o r e r  of physical  in  t h e amorphous  and  and  fusion.  a g i n g on t h e f o r m  e m p l o y e d DSC a l o n g w i t h  c r y s t a l l i z a t i o n were f o u n d i n 1000 t o  of  X-ray  o f r a d i a t i o n o n a m o r p h o u s PEEK.  samples w h i c h had been g i v e n r a d i a t i o n doses o f  the  sulfide).  PEEK a n d t h e r e s p e c t i v e h e a t s o f c r y s t a l l i z a t i o n  These a u t h o r s the glass  Scanning C a l o r i m e t r y  Lower  the  5000 M r a d i n a 2  MeV e l e c t r o n b e a m . The DSC t e c h n i q u e was u s e d b y I t o  and P o r t e r  (26)  to  study  d r a w i n g t e m p e r a t u r e o f PPS: s a m p l e s w h i c h w e r e d r a w n a t l o w tures,  below the glass  crystallinity remained  3.3  while  transition,  were observed t o have  t h e undrawn and h i g h t e m p e r a t u r e  the  tempera-  stress-induced  drawn  samples  amorphous.  EXPERIMENTAL  The t h e r m a l a n a l y s i s o f Dr.  R.C.  Thompson o f  o f PEEK a n d PPS was p e r f o r m e d o n t h e  the Department o f Chemistry,  U.B.C.  equipment  This  equip-  - 27 -  m e n t was c o m p r i s e d o f a M e t t l e r tial it  scanning calorimeter  cell  TC-10A p r o c e s s o r a n d a DSC-20  o f t h e same make. The d a t a was p l o t t e d  was c o l l e c t e d b y a S w i s s M a t r i x p r i n t e r .  retained for  the numerical evaluation of  e n c a p s u l a t e d i n aluminum pans.  differen-  The m o s t r e c e n t  the events.  as  s c a n was  The s a m p l e s  were  The s a m p l e w e i g h t s w e r e k n o w n t o a n a c c u -  r a c y o f ± 0 . 0 2 mg, a n d v a r i e d f r o m a b o u t 8 t o 28 mg. A n e m p t y p a n was u s e d as t h e r e f e r e n c e Figure  standard.  3 . 1 shows a c r o s s - s e c t i o n a l  num s e n s o r a t  the l e f t  diagram o f  measures t h e t e m p e r a t u r e o f  the c e l l .  D  C  heater  x 0 D  C  T  Figure  3.1:  Pt  sensor  AT  signal  S e c t i o n a l v i e w o f DSC m e a s u r i n g  p u r g e g a s inlet  cell.  plati-  the furnace while  reference pan  sample pan  The  the  - 28 -  thermopile  l o c a t e d on t h e d i s k between t h e sample and r e f e r e n c e  records  the temperature  flow to  the  gradient  and t r i g g e r s  an a d j u s t m e n t  min"-'- f r o m 35°C t o a t  specified, least  50°C above t h e m e l t i n g  of  indium,  l e a d and z i n c and t h e h e a t  temperature c a l i b r a t i o n runs,  s a m p l e was c o n s i s t e n t  o b t a i n the Tg, T ,  3.4  the  of  indium. the  In  a  indium  m  values  as w e l l  TC-10A p r o c e s s o r was u s e d as t h e c r y s t a l l i z a t i o n  to  and  RESULTS AND DISCUSSION  Richardson  thermal analysis,  (45) w r i t e s :  "Even r e l a t i v e l y  t y p i f i e d by s c a l e l e s s  i n polymer c h a r a c t e r i z a t i o n ;  often sufficient ultimate  to  properties  c r u d e methods have p r o v e d o f  great  i s p r e s e n t and hence what  is  the  be."  a n a l y s i s b y DSC. The p r i m a r y o b j e c t i v e s  quantitative  i n t h e use o f  thermal  were to establish  of  t h e presence o r absence o f a peak  i n f e r what s t r u c t u r e will  ordinates,  I n t h i s w o r k no a t t e m p t was made t o do s e r i o u s  (i)  fusion  enthalpies.  J.M.  value  10 K  t o w i t h i n ± 0 . 1 K.  and T  c  of  f l o w c a l i b r a t i o n was  the temperature  The s o f t w a r e p r o v i d e d b y t h e M e t t l e r  melting  heat  point.  made u s i n g t h e h e a t o f f u s i o n o f a n e x a c t l y k n o w n mass o f of  the  t h e s a m p l e was h e a t e d a t a r a t e  The p l a t i n u m t h e r m a l s e n s o r was c a l i b r a t e d a g a i n s t  series  of  sample.  Unless otherwise  temperatures  pans  the p r i n c i p a l  transition  temperatures,  thermal  analysis  - 29 -  (ii)  to determine q u a l i t a t i v e l y amorphous,  (iii)  to detect  the annealing o f  The DSC a n a l y s i s w h i c h were f u r t h e r  K.min" ). 1  for  t h e s a m p l e was c r y s t a l l i n e  or  and  from the v a r i a b l e  Figures  if  t h e amorphous samples a f t e r  removal  t e m p e r a t u r e NMR p r o b e .  provided insight  into  the nature  of  the  samples  s t u d i e d b y NMR.  3.2 and 3.3  show DSC s c a n s o f PEEK a n d PPS ( h e a t i n g r a t e  Table 3.1 l i s t s  PEEK a n d PPS.  the t r a n s i t i o n temperatures  The t a b u l a t e d number r e p r e s e n t s  over 4 experiments.  and  4  enthalpies  the average  taken  The t e m p e r a t u r e m e a s u r e m e n t s w e r e c o n s i s t e n t  to  w i t h i n ± 0 . 5 ° C a n d t h e e n t h a l p y v a l u e s v a r i e d b y a b o u t 10%. I n some c a s e s , literature.  the  Variations  thermal h i s t o r i e s  of  transition likely  temperatures  reflect  differ  from those of  varying molecular weights  t h e samples r a t h e r  t h a n an a c t u a l e r r o r  in  measurements.  t -  Figure  3.2:  DSC s c a n o f PEEK (a) amorphous (heating rate 4 K min" ). 1  (b)  *40°C  crystalline  and the  the  - 30 -  X- m °c A  Figure 3.3:  DSC scan of PPS (a) amorphous (heating rate 4 K min" ).  (b) crystalline  1  Table 3.1:  DSC Results f o r PEEK and PPS.  PEEK  PPS  T  g  [°C]  143 5  87 2  T  c  r c ]  173 1  121 7  22 9  25 4  340 3  282 0  43 1  42 9  AH T  [°C]  m  AH  [Jg" ] 1  C  m  [Jg'l]  - 31 -  3.4.1  The G l a s s T r a n s i t i o n  The f i r s t a n d PPS, i s the p o i n t point  of  event,  the glass  only  transition.  i n f l e c t i o n of  the t r a n s i t i o n  of a typical  visible  Temperature  is  i n t h e a m o r p h o u s s a m p l e s o f b o t h PEEK The t r a n s i t i o n t e m p e r a t u r e  is  t a k e n as  the curved drop i n heat c a p a c i t y ;  at  this  50% c o m p l e t e  Tg c u r v e and t h e p o i n t s  (46)  Figure  3.4  shows t h e  c a l c u l a t e d by the  sketch  Mettler  processor.  T  Figure  3.4:  S k e t c h o f a DSC g l a s s  transition  curve.  Samples w h i c h w e r e a n n e a l e d i n t h e T g r e g i o n e x h i b i t istic  e n d o t h e r m i c p e a k o b s e r v e d b y Kemmish a n d Hay ( 3 4 ) .  presents held at  the glass  transition  the  character-  Figure  3.5  o f a n a m o r p h o u s PEEK s a m p l e w h i c h h a d  137°C i n t h e NMR p r o b e .  The e n d o t h e r m i c p e a k i s  quite  been  - 32 -  pronounced. plastics  to superheat,  "catch-up"  height while  common t o a g r e a t many a m o r p h o u s  (47). The a n n e a l i n g a l l o w s  which tends the  T h i s phenomenon i s  of  period of  the peak i s  t h e maximum o f  20°C b e l o w  formation of a lower enthalpy  and t h e e n d o t h e r m i c peak above Tg the glass  thermo-  as i t  returns  represents  to equilibrium.  a f u n c t i o n o f a n n e a l i n g t i m e and  glass,  The  temperature,  the peak g e n e r a l l y occurs a t a t e m p e r a t u r e  15  to  T„.  I I  J  Figure  3.5:  DSC g l a s s 137°.  transition  curve f o r  a m o r p h o u s PEEK a n n e a l e d  at  - 33 -  3.4.2  Crystallization  The s e c o n d t h e r m a l e v e n t i s samples;  it  is  the c r y s t a l l i z a t i o n  l i z a t i o n exotherm i s Tg.  also exhibited only  smaller  for  e x o t h e r m . The a r e a o f  lization work,  is  seen.  the c o r r e c t baseline  the l i n e s  of  the baseline  assumption t h a t  (baseline  type 8 ) .  Figure  Implicit  c  above T , c  d e s i r e d i n t h i s work, In actual fact,  it  is  3.6  in this  temperatures below T ,  and a t t e m p e r a t u r e s  the l i n e s  fully  the assumption i s  shows a n  the end o f enthalpy,  fully  crystallized.  For the  "  [H(amor.,  the enthalpy  Thus,  to f i n d a true  x  is  the  amorphous accuracy  difference at  the  - H(cryst.,  T )] 2  -  2  at  crystallization  t h e amorphous  d u r i n g t h e c r y s t a l l i z a t i o n must be  T )  the  adequate.  T  ^cryst  of  choice of baseline  t h e c h a n g e i n e n t h a l p y due t o h e a t i n g o f regions  peak  and t h e c o m p l e t e l y c r y s t a l l i z e d p o l y m e r ,  the endothermic peak.  crystalline  either  illustration  t h e sample i s  the i n t e g r a t e d area i s  the endotherm,  on  as p a r t  b e t w e e n t h e amorphous p o l y m e r a t t h e o n s e t o f c r y s t a l l i z a t i o n beginning of  this  t h e n b e i n g c u r v e d t o meet b e n e a t h t h e  construction. at  crystal-  In  (44).  maximum. T h i s p e a k i n t e g r a t i o n c a l c u l a t i o n was a v a i l a b l e Mettler processing  crystal-  problem i n c a l c u l a t i n g the enthalpy of  the determination of  the event,  the  no e x o t h e r m i s  t h e b a s e l i n e was f o u n d b y t h e e x t r a p o l a t i o n o f  side of  amorphous  samples w h i c h have b e e n a n n e a l e d above  I n a s a m p l e o f maximum c r y s t a l l i n i t y , The m o s t d i f f i c u l t  i n the  and  subtracted:  T  2  [/ xC dT + / Tl T  (l-x)C  p c  p a  dT]  X  (3.1)  - 34 -  Figure  3.6:  T]_ t o T2 i s temperature, regions  DSC c r y s t a l l i z a t i o n  the range o f C  p c  and x i s  and C  p a  e x o t h e r m f o r a m o r p h o u s PPS.  the c r y s t a l l i z a t i o n  endotherm,  are the heat c a p a c i t i e s  the c r y s t a l l i n e  weight  of  the  T  is  c  the  pea  amorphous  f r a c t i o n which i s  a  function  temperature. For the f u l l y therm i s  23 J g " l  a m o r p h o u s PEEK s a m p l e ,  the  integration of  which agrees v e r y w e l l w i t h t h a t  of  22 J  the  g"  1  exo-  - 35 -  previously  reported  (34).  B e c a u s e t h e a m o r p h o u s PPS was o n l y a v a i l a b l e AH  C  value,  expressed i n J g "  1  of  s a m p l e , was a d j u s t e d t o t h e  f r a c t i o n o f PPS i n t h e g l a s s / P P S  3.4.3  and t h e  polymers.  event,  weight  composite.  polymers  (crystallized  I n simple c r y s t a l l i n e  temperatures  the broadness  of  systems, and t h i s  t h e DSC c u r v e .  356°C, p e a k i n g a t  of  peak a t  the melting  any sample c o n t a i n s  the baseline  i n the  crystal-  regions which  The m e l t i n g o f PEEK i s  340°C. and f o r  a melting  temperature.  range o f m e l t i n g p o i n t s  the heat o f f u s i o n o f  the c r y s t a l l i z a t i o n  evident  a DSC s c a n r e c o r d s  is  is  melt  f r o m 265°  t h e same t y p e o f e r r o r s  as due  SUMMARY OF DSC WORK  sulfide)  established values of glass  to  these m e l t i n g peaks y i e l d s  a s s u m p t i o n s a r e made.  DSC m e a s u r e m e n t s o f p o l y ( e t h e r  in  from  the polymers. Again, j u s t  exotherm c a l c u l a t i o n ,  Since  reflected  detected  PPS, t h e r a n g e  2 9 8 ° C , p e a k i n g a t 2 8 2 ° C . The i n t e g r a t i o n o f crude estimate  is  i n t h e c o u r s e o f t h e DSC s c a n )  materials,  distinctive  are imperfect  at various  300°C t o  the melting t r a n s i t i o n ,  'amorphous'  e n d o t h e r m as a s h a r p ,  3.5  the  Melting  The f i n a l line  as a c o m p o s i t e ,  ether ketone) transition,  and  poly(phenylene  crystallization  and  a in to  - 36 -  melting point  temperatures  for  these p a r t i c u l a r  w i t h i n the ranges found i n the l i t e r a t u r e . of  samples.  Estimates  The v a l u e s  of  the  it  provided  were  enthalpies  f u s i o n a n d o f c r y s t a l l i z a t i o n w e r e a l s o made. The m o s t i m p o r t a n t  simple q u a l i t a t i v e  aspect o f  t h i s w o r k was t h a t  way t o d e t e r m i n e  the thermal h i s t o r y  of  a  the  polymer  show no g l a s s  transi-  samples: (i)  Samples c r y s t a l l i z e d  to the f u l l e s t  t i o n or c r y s t a l l i z a t i o n (ii)  extent  exotherm.  C o m p l e t e l y amorphous samples e x h i b i t b o t h t h e e v e n t s a b s e n t  in  (i). (iii)  Samples w h i c h have undergone a n n e a l i n g a t o r j u s t b e l o w t h e show a s h a r p e n d o t h e r m i c  spike  immediately a f t e r  the glass  Tg transi-  tion. (iv)  Samples w h i c h h a v e b e e n a n n e a l e d a t h i g h e r reduced c r y s t a l l i z a t i o n  exotherm.  temperatures have  a  - 37 -  4.  4.1  HIGH RESOLUTION  1 3  C NMR STUDIES  INTRODUCTION TO CP/MAS NMR  The a p p l i c a t i o n o f h i g h r e s o l u t i o n n u c l e a r m a g n e t i c r e s o n a n c e the study o f p l a s t i c s  began i n the l a t e  1950's.  S o l u t i o n NMR s t u d i e s  s m a l l m o l e c u l e s w e r e w e l l u n d e r w a y when p o l y m e r c h e m i s t s c h a r a c t e r i z e m a c r o m o l e c u l e s b y NMR s p e c t r o s c o p y ; prisingly  successful.  limited to solutions solvents)  until  However, h i g h r e s o l u t i o n , (polymer melts or polymers  1975 when S c h a e f e r a n d S t e j s k a l  breakthrough to high resolution, CP/MAS e x p e r i m e n t .  tropic  shift  broadening,  tems.  zeolites, Synthetic  materials  dramatic the  decoupling,  the  angle  individual  i n massive d i p o l a r  and a n i s o -  distinguishable. poly(methyl  Polymers were t h e p r i m a r y  the h i g h r e s o l u t i o n technique.  samples  During the  t h e CP/MAS e x p e r i m e n t h a s b e e n a p p l i e d t o a w i d e r a n g e polymers  o f many t y p e s , w o o d , c e l l u l o s e ,  organo-metallic  lignin,  complexes and v a r i o u s b i o l o g i c a l  p o l y m e r s h a v e c o n t i n u e d t o b e among t h e m o s t  f o r NMR s t u d i e s .  sur-  were  dubbed "magic of  to  organic  ( 4 8 ) made t h e  s t u d i e d by Schaefer and S t e j s k a l were  and s o l i d p o l y s t y r e n e .  solid material: soils,  the signals  w e r e now c l e a r l y  used i n the p i o n e e r i n g o f ten years,  studies  dissolved in  and a t e c h n i q u e  which had h i t h e r t o been l o s t  The s a m p l e s f i r s t methacrylate)  polymer  of  began  C NMR s p e c t r o s c o p y o f s o l i d s ,  The s p e c t r a w e r e a m a z i n g ;  carbon types,  first  t h e r e s u l t s were  The new e x p e r i m e n t r e q u i r e d p r o t o n  proton-carbon cross-polarization, spinning".  1 3  to  No d o u b t t h e c o n t i n u e d i n t e r e s t  last  of coals, sys-  popular  i n and a p p l i -  - 38 c a t i o n o f NMR i s nature,  their  are widely  due t o t h e  inherent  suitability  and m o d i f i c a t i o n s  s i d e band s u p p r e s s i o n ,  h a v e b e e n made t o  r e l a x a t i o n t i m e measurement, All  the  time,  'off-angle', of  slow  these employ The  i n the  High r e s o l u t i o n , f o r polymer  study.  provides  1 3  C NMR i s  a very attractive  method  i n f o r m a t i o n about the chemical  the morphology and the m o l e c u l a r m o t i o n o f tacticity  dis-  chapter.  solid state,  It  the  first  t h e above e x p e r i m e n t s were used i n t h i s w o r k and w i l l be  the  which  original  contact  now a r o u t i n e m e t h o d o n many i n s t r u m e n t s .  cussed subsequently  spectra  variable  d o u b l e r e s o n a n c e a n d 2D e x p e r i m e n t s .  CP/MAS t e c h n i q u e ,  cases,  macromolecular  available.  p r o c e d u r e p r e s e n t e d by Schaefer and S t e j s k a l :  three of  their  immense c o m m e r c i a l i m p o r t a n c e a n d t h e n u m e r o u s t y p e s  Many e x t e n s i o n s  spinning,  of  the sample,  and,  structure,  in  special  o f t h e p o l y m e r c a n a l s o be i n f e r r e d f r o m CP/MAS  (49).  Spectra of  s o l u b l e polymers are g e n e r a l l y obtained i n the  solution  s t a t e b e f o r e c o l l e c t i o n o f a h i g h r e s o l u t i o n s o l i d spectrum and i t usual that  the chemical s h i f t s  found i n s o l u t i o n spectra are  similar  those of  Differences,  to  informative.  the s o l i d .  For example,  may c a u s e t h e s p l i t t i n g tion;  atoms e q u i v a l e n t  lattice shape, give occur  solid state effects  of a s i g n a l which i s  different  into  s y s t e m . The u l t i m a t e  material  goal of  sites  of  solu-  the  Line-  the  frequencies  in  in  environments.  investigations  t h e m o r p h o l o g y and t h e m o t i o n a l  i n the polymer  c a n be  f o u n d as a s i n g l e t  electronic  r e l a x a t i o n and c r o s s - p o l a r i z a t i o n  quite  in a crystalline  i n s o l u t i o n can occupy d i f f e r e n t  and thus e x p e r i e n c e  insight  when o b s e r v e d ,  is  polymers which  these studies  is  to  - 39 correlate  the molecular  properties. the s h i f t  Thus,  for  example,  from d u c t i l e  terephthalate)  dynamics o f  the m a t e r i a l w i t h  Sefcik et a l .  to b r i t t l e  is  molecular motion i n the m i d - k i l o h e r t z  mechanical  (50) have suggested  impact f a i l u r e  caused by a n n e a l i n g ,  its  of  related to frequency  poly(ethylene  the disappearance  results,  compatibility concern.  that  of polymeric blends.  one o f c o n s i d e r a b l e  interest  The n a t u r e and i s  d e s i g n o f new b l e n d s .  may b e a d i f f i c u l t  In general,  parameter  t u r e may e x h i b i t compatibility  (i)  of blend compatibility:  o f one p o l y m e r  u s e d t h e CP/MAS t e c h n i q u e s  p o l y (phenylene o x i d e ) . r e l a x a t i o n times) Because o f  of  may show ( i i )  to study blends  obtained f o r blends of  of polystyrene  the T ^ s  in al.  and  (rotating  frame  the  ( w i t h i n a r a n g e o f a b o u t 1 n m ) . The p r o -  However,  different  polymers.  Therefore,  not absolutely complete,  this  from  the proton T i ^ s  t h e s e two p o l y m e r s c o r r e s p o n d e d t o t h e  individual if  partial  the p r o t o n T i ^ s are v e r y dependent upon  those measured f o r p o l y ( p h e n y l e n e - o x i d e ) .  an e x t e n s i v e ,  mix-  t h e p r o t o n s a t t a c h e d t o c a r b o n atoms were measured.  spin diffusion,  the  employed.  Schaefer e t  t o n T^pS m e a s u r e d f o r p o l y s t y r e n e w e r e f o u n d t o b e q u i t e  of  is  appear  type are found dispersed  By c r o s s - p o l a r i z a t i o n ,  immediate magnetic environment  values  compati-  the polymer  the second, w i t h m i x i n g only a t the r e g i o n b o u n d a r i e s ) . (51)  more  t o d e t e r m i n e as t h e r e s u l t s  complete homogeneity or i t  (small regions  industrial  lead to  technique  and  blend  the degree o f b l e n d  t o b e somewhat d e p e n d e n t u p o n w h i c h i n v e s t i g a t i v e There a r e two c l a s s i f i c a t i o n s  of  unique  also of  The u n d e r s t a n d i n g o f p o l y m e r m i s c i b i l i t y w i l l  effective bility  is  is  of  range.  A s e c o n d a r e a o f p o l y m e r s w h e r e s o l i d s t a t e NMR y i e l d s helpful  that  agreement  averaged indicated  m i x i n g between t h e two  chains.  - 40 -  S o l i d s t a t e NMR i s intractible  polymers  of particular  s u c h as PEEK, PPS o r p o l y i m i d e s ,  thermosetting network polymers, o f Garroway the study of  (52,53)  its  ability  as p r o v i d i n g  4.2  4.2.1  the cured r e s i n s .  o n DGEBA e p o x y r e s i n s  these m a t e r i a l s  are i n s o l u b l e ,  advantage i n the study  and t h e r e f o r e  to determine  is  and a l s o  The e a r l y  The E n e r g y  1 3  C  is worthy of note.  Generally,  severely c u r t a i l e d by the f a c t  solid state  the s t r u c t u r e  of these macromolecules, the  as  for  well  systems.  Interactions  o f an a t o m i c n u c l e u s o f s p i n 1/2 of  p l a c e d i n a mag-  f i e l d are determined by a s e r i e s  (i)  t h e Zeeman i n t e r a c t i o n o f t h e m a g n e t i c n u c l e u s w i t h t h e  interactions: magnetic  (Z).  the I n t e r a c t i o n of  the nuclear  surrounding magnetic n u c l e i (iii)  the  (iv)  the scalar  i n t e r a c t i o n due t o  dipole w i t h the dipoles  of  any  (D).  the chemical s h i f t  coupling interaction  The s p i n H a m i l t o n i a n f o r follows:  they  CP/MAS NMR i s h i g h l y v a l u e d  netic  (ii)  that  NMR THEORY  The e n e r g y l e v e l s  field  for  CP/MAS w o r k  i n f o r m a t i o n about t h e morphology and m o t i o n o f  SOLID STATE  of  anisotropy  (CSA),  and  (SC).  s u c h a s y s t e m c o u l d t h e n b e e x p r e s s e d as  - 41 -  H  4.2.1a  The Zeeman  -  H  Generally,  order of  10^ t o  it  is  10^ Hz.  two d i s t i n c t  7hH, where 7 i s the magnetic  It  levels.  the p r i n c i p a l  is  ( o f s p i n 1/2)  The d i f f e r e n c e  strength.  ratio,  ration.  the population difference  For t h i s  spectrum of  4.2.1b  as t h e f i e l d  improved s i g n a l - t o - n o i s e  The d i p o l a r  (either  (8)  the the  to  split  this  increases also  constant  is  and H  interaction  is  linear  so d o e s t h e e n e r g y  sepa-  increases between the  f i e l d usually results  is  in  two a  ratio.  Interaction  has i t s  own l o c a l  or negatively)  neighbouring dipoles. the angle  field  i n t e r a c t i o n a r i s e s when a m a g n e t i c n u c l e u s  as a d i p o l e , postively  a strength in  Planck's  presence o f o t h e r n u c l e i w h i c h a l s o have n o n - z e r o nucleus,  interac-  between these energy l e v e l s  reason a h i g h e r magnetic  The N u c l e a r D i p o l e  t h e above  i n a magnetic  The m a g n i t u d e o f  strength;  levels.  one o f  h is  w i t h the f i e l d Thus,  (4.1)  S C  t h e Zeeman i n t e r a c t i o n w h i c h c a u s e s  the gyromagnetic  field  + H  C S  has t h e g r e a t e s t m a g n i t u d e ,  energy o f a magnetic nucleus into  + H  D  Interaction  The Zeeman i n t e r a c t i o n tions.  + H  Z  The m a g n i t u d e o f  between the p r i n c i p a l  this  magnetic  in  the  s p i n . A magnetic  f i e l d and t h i s  to the net  is  field  contributes  f i e l d experienced by  the  c o n t r i b u t i o n depends  upon  field,  H, a n d t h e  inter-  - 42  dipole vector,  and i s  between the d i p o l e s  -  inversely proportional  3 (rj^)•  Thus,  t o t h e cube o f  the c o n t r i b u t i o n  t h e f i e l d o f d i p o l e k may b e w r i t t e n  j (B ) z  the  distance  of dipole j  to  as:  j B  z  -  <1 - 3cos 0>  (4.2)  z  r k j 3  w h e r e fi  z  is  t h e m a g n e t i c moment a n d t h e  average over molecular m o t i o n . this  interaction.  the complete must be  Figure  The f i g u r e  interaction,  angular brackets  Figure 4.1 gives  a vector  denote  schematic  shows o n l y one s u c h i n t e r a c t i o n ,  the e f f e c t  of a l l  but  of for  the dipoles which surround  included.  4.1:  the  The i n t e r a c t i o n o f t w o d i p o l a r n u c l e i , j , k i n presence of a s t r o n g magnetic f i e l d , B . Q  the  k  - 43  In a realistic  case,  -  d i p o l e k w o u l d be o f a  1 3  C nucleus  and j , o f  a  13  proton.  • -C nuclei L  ,  t h e case o f  are s u f f i c i e n t l y  the ^ C n u c l e i , 3  O n l y t h e C-H d i p o l e this  the  1 3  C  dilute  i n n a t u r a l abundance t h a t  dipole  i n t e r a c t i o n c a n be  i n t e r a c t i o n needs t o be c o n s i d e r e d .  i n t e r a c t i o n c a n be as l a r g e as 10-* Hz ( 4 9 ) .  i n a s o l i d sample i s positions  of  the surrounding proton dipoles,  different  magnetic  f i e l d and c o r r e s p o n d i n g l y  resonance frequency. resonance s i g n a l  4.2.1c  The f i n a l  i n the  magnetic  is  Anisotropy  reason,  diagnostic'  is  the chemical s h i f t  introduces  but  a n i s o t r o p y becomes  The a r r a n g e m e n t o f  the n u c l e i  In solid state  a problem of  the chemical s h i f t  the chemical s h i f t  a  atom the  slightly  different the  ^ C 3  the e l e c t r o n s  external  interaction and t h e  is  very  molecular  the observed atom.  are c e r t a i n l y  the r a p i d tumbling of molecules  dependence o f  This  from the  exceedingly useful  Chemical s h i f t s  r e s o l u t i o n s o l u t i o n spectroscopy.  uid state  responds t o a  u p o n t h e atoms b o n d e d t o  the chemical s h i f t technique.  C  of  Interaction  dependent upon the chemical environment o f  this  each e x p e r i e n c e s  due t o t h e s h i e l d i n g o f t h e n u c l e i  particularly  1 3  d e f i n e d by  to broaden g r e a t l y  f i e l d by the surrounding e l e c t r o n s .  structure,  The m a g n i t u d e  solid.  The C h e m i c a l S h i f t  The CSA i s  effect  ignored.  Because each  i n a unique magnetic environment,  in  as a  'chemical  a key p o i n t  spectroscopy  l i n e broadening. averages a l l  the  For  in  high  however, I n the  liq-  directional  i n the s o l i d state the e f f e c t  of  apparent. about a nucleus  i s never  spherical  - 44 -  since  it  depends upon t h e n a t u r e and p o s i t i o n o f  which the electron d i s t r i b u t i o n example,  the e l e c t r o n i c a l l y  i n Figure 4.2.  is highly  directional.  highly directional  The i n t e r a c t i o n o f  t h e m o l e c u l a r bonds Consider,  in  for  c a r b o n y l b o n d , as  shown  the electrons w i t h the nucleus  varies  O  II  _A_  c=o  JL  Hi  H-  Figure 4.2:  ( a ) The t w o e x t r e m e o r i e n t a t i o n s the a p p l i e d magnetic f i e l d .  pect  to  to  The c h e m i c a l s h i f t a n i s o t r o p y p a t t e r n a r i s i n g f r o m t h e random d i s t r i b u t i o n s o f o r i e n t a t i o n s i n a p o l y c r y s t a l l i n e sample.  (c)  t h e s o l u t i o n spectrum showing an i s o t r o p i c  frequency  the p r i n c i p a l  shielding  t h e bond r e l a t i v e  (b)  markedly w i t h the angle of the bond, r e l a t i v e The r e s o n a n c e  of  factor  is  a function of  field.  a so t h a t  "j  to the p r i n c i p a l  2  J B  0  field.  (l-aj)  res-  the bond determines  the resonance c o n d i t i o n o f  r /  (49).  the bond o r i e n t a t i o n w i t h  The o r i e n t a t i o n o f  -  signal  the nucleus  the  is:  (4-3)  - 45  where B  is  Q  the p r i n c i p a l magnetic  netic  s h i e l d i n g which i s  shift  value 6 is  resonance  -  f i e l d a n d trj  t h e c o m p o n e n t o f mag-  a l i g n e d along the f i e l d d i r e c t i o n .  e x p r e s s e d as t h e d i f f e r e n c e  "j — -  =  " "TMS  x  The  chemical  i n ppm b e t w e e n »>j a n d  f r e q u e n c y o f some s t a n d a r d m a t e r i a l  S  is  (usually  10  the  TMS):  ,  (4.4)  6  "TMS  The v a l u e o f c i p a l magnetic 1 3  C  6 is  field.  atoms i n n e u t r a l  4.2.Id  The S c a l a r  The s c a l a r considerably  The s h i f t solids  is  Coupling  anisotropies  to  the s t r e n g t h o f  typically  of the order o f  200 ppm  the  smaller  prin-  experienced by (54).  Interaction  or s p i n - s p i n c o u p l i n g i n t e r a c t i o n between n u c l e i  be n e g l e c t e d i n t h i s  4.2.2  linearly proportional  than the other treatment  interactions  is  of equation 4 . 1 . I t  may  o f s o l i d s t a t e NMR.  The CP/MAS E x p e r i m e n t  The a i m o f solid state the l i q u i d average out  is  the h i g h r e s o l u t i o n ,  NMR s p e c t r o s c o p i s t w o r k i n g i n  t o mimic t h e random m o t i o n s w h i c h a r e c h a r a c t e r i s t i c  state.  In liquids,  the d i p o l e - d i p o l e  these  isotropic  interactions  motions  the of  serve very w e l l  and t h e c h e m i c a l  shift  to  - 46 -  anisotropy which,  i n the s o l i d s t a t e ,  are the source o f extreme  line  broadening. There are e s s e n t i a l l y (i)  c r o s s - p o l a r i z a t i o n which a l l e v i a t e s  from the d i l u t e carbon n u c l e i , spinning,  4.2.2a  1 3  that  C n u c l e i and a l s o  and ( i i )  t h e weak  the long r e l a x a t i o n time o f  h i g h power d e c o u p l i n g and ( i i i )  abundance o f  the proton.  assures  two  1 3  are r a r e l y  dipole effect.  d i s a d v a n t a g e because i t The  1 3  the  the  leads  magic  signal the  angle  interactions.  --'C n u c l e u s  that  siderably lattice than f o r  is  is  of  i n so c l o s e a p r o x i m i t y the n a t u r a l  for  is  than the p r o t o n r e l a x a t i o n . is  the  for  1 3  c o l l e c t i o n of  also  a  the  moment  the s e n s i t i v i t y  of  reduced.  The  sec-  C nucleus  is  con-  For c a r b o n ,  t h e T^  A long relaxation  s p e c t r a because i t  exhibit  The m a g n e t i z a -  t y p i c a l l y b e t w e e n 10 a n d 100 t i m e s (55).  it  c a r b o n NMR.  the magnetic  further  relaxation rate of  as t o  the proton 6 from  t h e p r o t o n moment,  a p r o t o n i n t h e same m o l e c u l e  inefficient  a vis  hundredth  abundance i s  t h e m a g n e t i c moment.  to proton spectroscopy  r e l a x a t i o n time)  one  advantage because  t o a v e r y low s e n s i t i v i t y  a quarter  the s p i n - l a t t i c e  slower  1.11%,  d e p e n d e n t o n t h e moment a n d s i n c e  c a r b o n NMR r e l a t i v e ond i s  is  a great  C n u c l e u s has o t h e r drawbacks v i s  linearly J  C nucleus  However,  o f v i e w o f NMR. The f i r s t is  1 3  Such a l o w a b u n d a n c e i s  C nuclei  any h o m o n u c l e a r  tion  the problems o f  experiment:  Cross-Polarization  of  point  t h e CP/MAS  b o t h o f which reduce the l i n e broadening  The n a t u r a l  of  t h r e e components o f  necessitates  (spinlonger time  is  t h e use  of  - 47  long recovery All  times between pulse  these d i f f i c u l t i e s  essence o f  -  sequences.  are e l i m i n a t e d by c r o s s - p o l a r i z a t i o n .  the c r o s s - p o l a r i z a t i o n experiment  is  z a t i o n from the abundant p r o t o n s p i n system t o system.  For the t r a n s f e r  to occur,  This  a n d t h e 1-H n u c l e i ,  locking the spins  (56)  it  simply  H H  t o each o t h e r  -  t h e two s p i n  the  i n the x ' , y '  C  1 3  ^ C 3  refercondition  (4.5) C  where 7  and 7 are the respective gyromagnetic r a t i o s H C represent the appropriate l o c k i n g f i e l d along the y'  H  of  systems  H  1 3  l  carbon  stated:  7  H  magneti-  abundant  r e f e r r e d t o as t h e H a r t m a n n - H a h n is  L  X  of  achieved by matching the energies  This matching is  and m a t h e m a t i c a l l y ,  the less  the energies o f  m u s t b e t h e same.  ence p l a n e .  is  the t r a n s f e r  The  1 3  and H and ^-H a x i s . Since  C 7 / 7 - 4 / 1 , one may r e a d i l y see t h a t t h e l o c k i n g f i e l d o f t h e c a r H C bons must be 4 t i m e s t h a t o f t h e h y d r o g e n l o c k i n g f i e l d . I n t h i s matched 1 3  X  1 3  condition,  the energy r e q u i r e d f o r  the p r o t o n s p i n - f l i p  is  identical  to  13 that  for  a  C spin-flip.  spin distribution little  of  The d i l u t e  the protons,  but  s y s t e m a d o p t s t h e more  favourable  t h e much l a r g e r p r o t o n s y s t e m  is  a f f e c t e d by the carbon system.  Figure 4.3  illustrates  the procedure  for  the  cross-polarization  experiment: (a)  shows t h e i n i t i a l  p r i n c i p a l magnetic x'  proton magnetization aligned along H ,  f i e l d before  d i r e c t i o n which t i p s  0  the  t h e a p p l i c a t i o n o f a 90° p u l s e a l o n g  the magnetization to the y '  axis,  (b)  and  (c)  the  - 48 -  a  Figure 4 . 3 :  b  e  d  The cross-polarization experiment, showing the behaviour of the and C magnetization vectors and the corresponding pulse sequence ( 5 7 ) . 1 3  (a) (b) (c) (d) (e)  i n i t i a l proton magnetization along Z. application of the spin locking pulse. increase i n C magnetization. acquire C FID. recycle time. 1 3  1 3  - 49  -  show t h e a p p l i c a t i o n o f t h e H a r t m a n n - H a h n m a t c h e d " r . f . p r o t o n and c a r b o n m a g n e t i z a t i o n a l o n g t h e y ' when t h e s p i n systems a r e l o c k e d ,  axis.  the amplitude  of  tion builds  up b y s p i n e n e r g y t r a n s f e r  (c).  t h e ^ C m a g n e t i z a t i o n has reached i t s  After  the decay o f no p u l s e s spins  to  is  the carbon magnetization.  are applied to e i t h e r their  duration of  removed,  of  is  time,  from (b)  to  to allow acquisition (e),  during  relaxation of  repetition of  the carbon spin l o c k i n g pulse  the  a p p r o x i m a t e maximum,  The d e l a y t i m e ,  equilibrium values before  lock  the carbon magnetiza-  s p i n system, permits  and t h e optimum l e n g t h o f t h e c o n t a c t transfer  (d),  to  During this  from the p r o t o n s ,  3  the carbon spin l o c k i n g pulse  pulse  of which the  the sequence.  c a l l e d the contact  time,  t i m e depends upon t h e r a t e o f  the magnetization from the proton to the carbon  The  the  spin  systems.  4.2.2b  Dipolar  Decoupling  The d i p o l e - d i p o l e s t a t e NMR. I n t h e  interaction experiment,  is it  a major broadening f a c t o r is  the heteronuclear  dipole  a c t i o n between t h e p r o t o n and t h e 1 C d i p o l e s w h i c h causes t h e Dipolar  decoupling is  of broadening.  is  causing t r a n s i t i o n s  The i n d u c e d s p i n f l i p p i n g  a v e r a g e d t o z e r o and t h e r e  dipole.  employed t o e l i m i n a t e  A strong decoupling f i e l d  the p r o t o n resonance, states.  successfully  is  is  applied at  inter-  this  type  the frequency  between the p r o t o n  sufficiently  solid  broaden-  3  ing.  of  rapid that  i s no e n e r g y i n t e r a c t i o n w i t h  of  spin the the  dipole  - 50 4.2.2c  Magic Angle  Spinning  M a g i c a n g l e s a m p l e s p i n n i n g r e m o v e s t h e l i n e b r o a d e n i n g due t o chemical s h i f t that  a n i s o t r o p y as w e l l  as r e s i d u a l  dipole coupling.  t h e CSA d e p e n d s o n t h e c h e m i c a l s h i e l d i n g f a c t o r ,  direction of  the p r i n c i p a l  magnetic  field,  r e l a t e d to s h i e l d i n g along the p r i n c i p a l  B .  This  Q  axes o f  o, zz  in  the  Recall the  s h i e l d i n g c a n be  the molecule  by:  3  °zz  where  is  the nuclear  the angle between B  axial  symmetry,  zz  the  uid spectra,  —  a  a  s  Q  ±  (4.6)  e  2  points  along the  For example,  ith  axis,  i n a molecule  can be e x p r e s s e d  c o s ^ + aj_ s i n ^ 2  Q  and  a . CT (|  z  z  =  <a>  shielding,  the a n i s o t r o p i c  3  -  (a  c a n a l s o b e w r i t t e n as  - a) L  with as:  the  component:  + a  (4.8)  a  t h e same as i s  is  1/3  2Z  and  (4.7)  2  and an a n i s o t r o p i c  isotropic  and a  o  zz  a  where a i s  c  •* o± a n d a3 - a ; a  2  the angle between B  sum o f a n i s o t r o p i c  a  and t h e a x i s .  Q  er^ = a  a  where # i s  I i i-1  s h i e l d i n g when B  6^ i s  let  "  observed i n the  p a r t w h i c h may b e e x p r e s s e d  (3cos ^ 2  -  1)  liqas:  (4.9)  - 51 -  This expression indicates  t h e dependence o f  term ( 3 c o s # - l ) .  this  2  54.7°,  the a n i s o t r o p i c  rotation of  if  term were s e t t o z e r o ,  contribution  that  shift is  if  t o t h e CSA w o u l d d i s a p p e a r .  t h e sample about an a x i s o f  a v e r a g e s e v e r y a n g l e <j> t o  tively this  Thus,  the a n i s o t r o p i c  54.7°  54.7°.  to  <j> w e r e Rapid  ( t h e magic a n g l e )  Figure 4.4 helps  on t h e  effec-  illustrate  concept.  z  R  Y  X  Figure 4.4:  Thus, the  The t i m e a v e r a g e d r e s u l t a x i s R (55).  the chemical s h i f t  isotropic  tion  spectrum.  rate  u  rates  sr  shift  o f a v e c t o r AB s p i n n i n g  observed i s  and t h e s o l i d s t a t e  'magically'  are o f t e n not p r a c t i c a l l y  reduced to  only  spectrum then resembles a s o l u -  For complete removal o f the a n i s o t r o p i c  must exceed the w i d t h o f  about  CSA,  t h e CSA p o w d e r p a t t e r n .  possible.  However,  rates  the  Such of  spinning spinning  less  than  - 52 -  half  t h a t value work q u i t e w e l l  ning sideband' tions  of  4.2.3  ^  s  r  signals  flank  to narrow the l i n e w i d t h s ,  the p r i n c i p a l  signal at  though  frequency  'spin-  separa-  .  Variations  o n t h e CP/MAS  Experiment  A h o s t o f NMR e x p e r i m e n t s h a v e b e e n d e v i s e d w h i c h a r e b a s e d u p o n t h e CP/MAS t e c h n i q u e . and v a r i a b l e  4.2.3a  contact  Dipolar  (59);  time.  of dipolar  the purpose o f  protonated carbon signals differs  from t h a t  of  d e p h a s i n g was d e v e l o p e d b y O p e l l a a n d F r e y the experiment  acquisition  The r e s u l t previously 1/r , 3  effect  is  the conventional  stated,  (Figure  that  is  the d i s t i n c t i o n  from the non-protonated.  a delay without proton decoupling is spectral  The p u l s e  CP/MAS e x p e r i m e n t  interaction  is  during the delay without  decoupling.  The s t r o n g  carbon magnetization.  the  sequence  i n one  respect, the  4.5).  the protonated carbon signals  on carbons bonded t o  of  introduced immediately before  the d i p o l a r  carbons,  dephasing  Dephasing  The p r o c e d u r e i n 1979  Two e m p l o y e d i n t h i s w o r k a r e d i p o l a r  the protons  The e f f e c t  are surpressed.  inversely  dependent  i s much w e a k e r o n t h e  upon  dipole-dipole  causes r a p i d dephasing o f  the  non-protonated  where t h e c a r b o n and h y d r o g e n n u c l e i a r e s u f f i c i e n t l y  far  As  - 53 -  90° PULSE  I  Figure 4.5:  apart,  The d i p o l a r d e p h a s i n g p u l s e before acquisition.  sequence s h o v i n g t h e  because t h e q u a t e r n a r y carbons e x p e r i e n c e v e r y l i t t l e  by d i p o l a r  delay  dephasing  interactions.  In addition to  internuclear  reduced by molecular motion.  It  distance, is  for  dipolar  this  carbons o f m e t h y l groups prone t o r o t a t i o n , dipolar  dephased  4.2.3c  The V a r i a b l e  The v a r i a b l e  interaction  reason t h a t will  is  signals  o f t e n appear  in  from the  spectrum.  C o n t a c t Time  contact  Experiment  time experiment  is  similiar  to the  dipolar  the  - 54 -  dephasing experiment  in that  it  provides  i n f o r m a t i o n about the  t i o n and immediate environment o f the carbon n u c l e i . polarization  technique,  the s p i n - l a t t i c e protons.  r e l a x a t i o n time  of  i n t e n s i t y versus  contact  C magnetization  involves  each w i t h a d i f f e r e n t  t y p e o f c a r b o n atom i n t h e  4.3  1 3  is  i n the r o t a t i n g frame  The e x p e r i m e n t a l p r o c e d u r e  CP/MAS s p e c t r a , plots  the rate of  I n the  contact  collecting time.  time are obtained,  protona-  cross-  dependent  (T^^)  of  the  a series  From t h e s e one p l o t  on  of  spectra, for  each  molecule.  EXPERIMENTAL  The h i g h r e s o l u t i o n CP/MAS e x p e r i m e n t s w e r e c a r r i e d o u t u s i n g B r u k e r CXP 200 MHz p u l s e d F o u r i e r the a p p r o p r i a t e l y  transform spectrometer,  equipped  t u n e d p r o b e c a p a b l e o f magic a n g l e sample  a with  rotation.  The o p e r a t i n g f r e q u e n c i e s w e r e 200 MHz f o r p r o t o n r e s o n a n c e a n d 5 0 . 3 MHz for  1 3  C  nuclei.  The c o n v e n t i o n a l CP/MAS s p e c t r a w e r e o b t a i n e d u s i n g t h e p u l s e sequence r e p o r t e d i n t h e l i t e r a t u r e a l s o shown i n F i g u r e 4 . 3  4.3.1  and Appendix  (54).  (The p u l s e  routine sequence  I.)  Rotors  The r o t o r s  u s e d i n t h i s w o r k w e r e t h e Beams-Andrew t y p e made  D e l r i n or of boron n i t r i d e .  The s t r o n g r e s o n a n c e s i g n a l  of  Delrin,  of  is  -  poly(oxymethylene), nal  for  at  t h e CP/MAS w o r k .  The b o r o n n i t r i d e  The p o w d e r e d c r y s t a l l i n e  ter f i l l  the r o t o r s . as t h e  the r o t o r  4.3.2  r o t o r has t h e  aesthetic  s a m p l e s o f PPS a n d PEEK w e r e p a c k e d  of the r o t o r s ,  disks  firmly  o f t h e same d i a m e -  a n d a s t a c k o f s u c h d i s k s was made  The s m a l l a m o r p h o u s PPS p e l l e t s w e r e p a c k e d c l o s e l y  a n d KBr u s e d t o f i l l  i n t h e gaps b e t w e e n t h e  to into  pellets.  Set-up  All  t h e s p e c t r a were o b t a i n e d w i t h the B r u k e r  programme.  L i q u i d b e n z e n e was u s e d f o r  and t u n i n g o f  the  t h e c a r b o n and p r o t o n t r a n s m i t t e r s .  benzene p r o t o n s u n t i l  the Fourier  s o f t w a r e CXPNMR  initial  accomplished by maximizing the off-resonance  free  spectrometer  M a g n e t s h i m m i n g was i n d u c t i o n decay o f  The 1 8 0 " p r o t o n p u l s e  e s t a b l i s h e d by a d j u s t i n g the p r o t o n gain o f the t r a n s m i t t e r FID appeared l e v e l w i t h t h e b a s e l i n e . assumed t o b e h a l f length for  the value of  The 90° p u l s e  t h e 180° p u l s e  t h e s e e x p e r i m e n t s was 6  length.  . The c o r r e c t  fields  o f 40G f o r  the  a n d 10G f o r  the  line-  l e n g t h was  until  l e n g t h was The 9 0 "  setting for  H a r t m a n n - H a h n c o n d i t i o n was a c h i e v e d u s i n g a s a m p l e o f External  set-up  t r a n s f o r m o f t h e FID y i e l d e d a  w i d t h o f a b o u t 3 0 - 4 0 Hz a t h a l f h e i g h t .  for  sig-  signal.  The PEEK f i l m was p u n c h e d i n t o  inside  the r o t o r .  -  8 8 . 9 ppm f r o m TMS was u s e d as t h e r e f e r e n c e  a d v a n t a g e o f h a v i n g no c a r b o n  into  55  the  then pulse the  adamantane.  the p r o t o n s were  required  spin-locking. The m a g i c a n g l e a d j u s t m e n t was made u s i n g p o w d e r e d K B r ,  following  - 56 -  t h e method o f Frye and M a c i e l  4.3.3  Pulse  programs  Appendix I  contains  and d e l a y times f o r  t h e p u l s e programs and g i v e s  contact  to eliminate baseline  nal-to-noise  (ii)  the dipolar  time experiments.  The n u m b e r o f ratio  the pulse  e a c h t y p e o f e x p e r i m e n t as p e r f o r m e d :  v e n t i o n a l CP/MAS e x p e r i m e n t , variable  (60).  All  and i n t e n s i t y  transients  (FIDs) were c o l l e c t e d  filled  to  programmes u s e d phase  artifacts.  i n blocks  Fourier  correct  of size  2K.  The f r e e  The F I D was  and e x p o n e n t i a l  transformation of  t h e FID t o  the  phasing.  then  RESULTS AND DISCUSSION  Poly(phenylene  sulfide)  The s p e c t r u m o f p o l y ( p h e n y l e n e quite  zero  multiplication  phased w i t h b o t h z e r o and f i r s t  order  sig-  induction  The r e s u l t i n g s p e c t r u m was  4.4.1  the  alternation  f r e q u e n c y d o m a i n was t h e n p e r f o r m e d .  4.4  con-  accumulated v a r i e d w i t h the d e s i r e d  32K a n d t h e b a s e l i n e  r o u t i n e s were a p p l i e d .  the  dephasing and ( i i i )  and t h e e x p e r i m e n t a l c o n d i t i o n s .  decays  (i)  lengths  straight  carbon atoms,  forward.  sulfide),  PPS c o n t a i n s  shown i n F i g u r e 4 . 6 ,  o n l y two m a g n e t i c a l l y  t h e d e c o u p l e d s p e c t r u m shows o n l y t w o p e a k s ,  is  distinctive at  1 2 9 . 1 ppm  - 57 -  and a t  1 3 1 . 5 ppm. The s p e c t r u m I s  spectrum of c r y s t a l l i n e the spinning rate of  dipolar  turned off, of  Figure 4.7(a)  shows t h e n o r m a l  PPS a n d t h e s p e c t r u m i n 4 . 7 ( b ) , a d e l a y o f 40 (is was  Before data acquistion,  spin-locking.  During t h i s  with  spectrum, w h i l e , a t i o n pathways,  is  dipolar  The  attenuated i n the  t h e q u a t e r n a r y c a r b o n s w h i c h have no e f f i c i e n t show e s s e n t i a l l y  cates conclusively  that  c a r b o n s o f PPS a n d t h a t the protonated  CP/MAS  d e p h a s i n g t i m e when t h e d e c o u p l e r  seen t o be s i g n i f i c a n t l y  no d e c r e a s e o f  intensity.  t h e p e a k a t 1 3 1 . 5 ppm i s  due t o t h e  the peak a t  correctly  1 2 9 . 1 ppm i s  This  4.6:  dephased relaxindi-  quaternary assigned  carbons.  S o l i d s t a t e CP/MAS s p e c t r u m o f s p i n n i n g sidebands ( * ) .  crystalline  is  signal  -A Figure  a  introduced,  the r e l a x a t i o n o f the p r o t o n a t e d carbons occurs.  these carbons  measure  t h e t w o s p e c t r a l p e a k s was made w i t h t h e a i d o f  spectrum of c r y s t a l l i n e  without  CP/MAS  kHz.  dephasing experiment.  dephasing.  conventional  PPS. The s p i n n i n g s i d e b a n d s w e r e u s e d t o  3.0  The a s s i g n m e n t o f  the simple,  PPS s h o w i n g  to  - 58 -  1 2  Figure 4.7:  (a) (b) (c)  The r e p e a t i n g u n i t o f PPS. The c o n v e n t i o n a l CP/MAS s p e c t r u m o f c r y s t a l l i n e PPS. The d i p o l a r d e p h a s e d s p e c t r u m o f c r y s t a l l i n e PPS ( d e l a y - 40 / i s ) .  Figure 4.8(a) PPS c o m p o s i t e . line  It  shows t h e h i g h r e s o l u t i o n s p e c t r u m o f is  considerably broader  composite  samples  powder  (Figure 4.8d).  phous,  showed a l i n e w i d t h o f  c  amorphous  than the spectrum of  crystal-  PPS. A l i n e w i d t h c o m p a r i s o n was made b y m e a s u r i n g t h e w i d t h s  t h r e e PPS g l a s s  T  the  The f i r s t  (Figure 4.8a,b,c) sample  15 ppm. Sample  a n d e x h i b i t e d no c r y s t a l l i z a t i o n  width of clearly  this  time.  The A H  C  of  this  the  crystalline  intermediate  above t h e g l a s s  amor-  ( c ) was a n n e a l e d a b o v e  e x o t h e r m i n a DSC s c a n ;  s e e n . The s e c o n d f o r m ( b ) was o f  crystalline  assumed t o be f u l l y  s a m p l e was 8 . 9 ppm. The t w o d i s t i n c t  prepared by annealing j u s t limited  (a),  and the  of  transition  the  spectral peaks  are  crystallinity, temperature  s a m p l e was 4 . 7 J / g , w h i c h i s  for  slightly  a  less  - 59 -  than h a l f  of  the c y s t a l l i z a t i o n  linewidth of average o f  this  of the other  crystallinity,  two f o r m s .  two peak w i d t h s were d i s t i n g u i s h i b l e  the  line  linewidth  Figure  At what i s  1 3 1 . 5 ppm a n d 2 . 3 3 ppm f o r  is  4.8:  first  a m o r p h o u s PPS. The  a function of  this  powdered  at half height:  the l i n e  approximate  The PPS v i r g i n r e s i n  i n the spectrum o f  the  at  the f u l l y  t h i r d s a m p l e was f o u n d t o be 1 1 . 4 ppm t h e  the widths  has t h e h i g h e s t  exotherm o f  at  1.45  1 2 9 . 1 ppm.  (d)  sample  ppm  for  Clearly,  crystallinity.  S o l i d s t a t e CP/MAS s p e c t r a o f PPS: (a) amorphous ( b ) and ( c ) intermediate c r y s t a l l i n t i e s (d) f u l l y c r y s t a l l i n e powder.  glance,  expected.  this  pattern of  The a m o r p h o u s s a m p l e  l i n e w i d t h appears c o n t r a r y is  capable o f g r e a t e r  to  molecular  - 60 -  m o t i o n a n d t h u s t h e a r g u m e n t o f Veeman e t a l . poly(oxymethylene), assumption t h a t that  (61),  m i g h t b e c o n v i n c i n g l y made:  the narrow l i n e  the broad s t r u c t u r e  from the c r y s t a l l i n e  is  that  i n the sample.  There  t h e s t u d y o f Bunn e t a l .  is  terephthalate)  (62)  on p o l y p r o p y l e n e ,  indicate  The m o s t p r e v a l e n t  f o r broadened l i n e s .  the d i s t r i b u t i o n of  I n t h e a m o r p h o u s PPS t h e r e to  factor.  It  other polymer  is  is  the  heterogeneous  range o f is  less  of  in  the  positions ordered  the polymer  of  t h e s e PPS  a  "are the  notably  spectra  the c r y s t a l l i n e  supported by the f i n d i n g o f s i m i l i a r  systems,  time,  is  suggest a s u p e r p o s i t i o n o f  on the narrow d o u b l e t o f  the work o f Dechter  o x i d e and t h e work o f Fyfe e t a l . Contact  it  frequency comparable t o  the line-shape  The l i n e - s h a p e s  b r o a d amorphous s i g n a l theory  that  and  Two f a c t o r s may b e  a much g r e a t e r  auto c o r r e l a t i o n  the l i n e w i d t h ,  informative.  This  (50)  (50).  In addition to  nent.  in  example,  chemical s h i f t s  comes a b o u t when t h e m o l e c u l a r m o t i o n s  decoupling f i e l d "  also  isotropic  is  for  s a m p l e . Homogeneous b r o a d e n i n g may a l s o b e  d e s c r i b e d by an e f f e c t i v e  is  lines.  t h e c a r b o n atoms b e c a u s e t h e m o r p h o l o g y  than i n the c r y s t a l l i n e  line  largely,  by Schaefer e t a l .  responsible  available  is  polymers,  the widest  sample.  and  out."  amorphous p o l y m e r w h i c h e x h i b i t s  b r o a d e n i n g due t o  natural  so much m o t i o n  anisotropy  However s u b s e q u e n t w o r k o n s e m i - c r y s t a l l i n e the study of poly(ethylene  seems a  a n i s o t r o p y broadened  the chemical s h i f t  averaged  "Then i t  on  due t o t h e a m o r p h o u s m a t e r i a l  a chemical s h i f t  regions  t h e amorphous m a t e r i a l but not completely,  is  ...  from research  (64)  on  (63)  on  the compo-  features  in  polyethylene  polyethylene.  as w e l l as s a m p l e c r y s t a l l i n i t y ,  plays a role  in  the  - 61 relative  appearance o f t h e two components  amorphous n u c l e i have f a s t e r obtained using shorter nature.  Because o f  times w i l l  the percent  display greater  crystallinity  be o b t a i n e d b y s i m p l e d e t e r m i n a t i o n o f nents  of  the p r o p o r t i o n s  t o make r e l i a b l e  the  spectra  amorphous  t h e sample can n o t of  i n the spectrum. A complete understanding o f T ^  system i s necessary i n order  Since  r o t a t i o n frame r e l a x a t i o n r a t e s ,  contact  this,  i n the spectra.  t h e t w o compo-  behaviour  estimates  of  of  the  the degree  of  crystallinity.  4.4.2  Poly(ether  ether  ketone)  The h i g h r e s o l u t i o n ^ C s p e c t r u m o f PEEK i s 3  plex  than that  inequivalent this far  larger greater  o f PPS. The r e p e a t i n g u n i t  carbon atoms, repeating unit challenge  for  made i n t h i s w o r k d i f f e r s literature  o f PEEK h a s s e v e n  as shown i n F i g u r e 4 . 9 ( a ) . is  that  the assignment o f  PEEK t h a n f o r  PPS.  magnetically  The c o n s e q u e n c e  of  t h e s p e c t r u m was a  In fact,  the  f r o m t h a t w h i c h was p r e v i o u s l y  assignment  reported in  the  (24).  Figure 4.9(b) trum o f c r y s t a l l i n e a l s o marked i n t h e I n order collected:  c o n s i d e r a b l y more com-  shows t h e c o n v e n t i o n a l h i g h r e s o l u t i o n , PEEK p o w d e r .  t o make t h i s  times.  f i r m the r e s u l t s  assignment o f  t h e peaks  specis  figure.  the d i p o l a r  varied contact  The f i n a l  CP/MAS  a s s i g n m e n t two f u r t h e r  types o f  spectra  dephased spectrum and a s e t o f s p e c t r a The v a r i a b l e  of the d i p o l a r  contact  dephasing  having  time spectra served to experiment.  were  con-  - 62 -  o-<uv-o^(n>-c— 4  3  o  i—| i i — i — r — | — i — i — i — i — | — r 250 200 150  Figure 4 . 9 :  i | i i i i | i i 100 50  n  -j—r-i— 0 PPM  (a) The repeating u n i t of PEEK. (b) The s o l i d state CP/MAS spectrum of c r y s t a l l i n e PEEK. (* denotes the s i g n a l due to d e l r i n ) .  Comparison o f t h e dephased spectrum w i t h t h e c o n v e n t i o n a l cates  a reduction  one i n d i -  i n t h e p e a k a t 1 3 2 . 2 ppm a n d t h e d i s a p p e a r a n c e  peak a t 1 1 9 . 0 ppm. (See F i g u r e 4 . 1 0 . ) protonated carbons:  These p e a k s w e r e a s s i g n e d t o t h e  C - 3 , C - 4 a n d C - 7 . The i n t e n s i t y  ppm was n o t r e m o v e d b u t r e d u c e d b y a b o u t h a l f , protonated carbon also contributes  o f the  of the line  indicating  to the signal.  that  a t 132.2 anon-  - 63 -  I  ~i—i—|—i i i i | i i i i—|—i—i i i | i i i i j i i i i • [ — i i i 250 200 150 100 50 0 PPM Figure 4.10:  ( a ) The c o n v e n t i o n a l CP/MAS s p e c t r u m o f c r y s t a l l i n e PEEK. ( b ) The d i p o l a r d e p h a s e d s p e c t r u m o f PEEK ( d e l a y - 40 p s ) . ( * d e n o t e s t h e s i g n a l due t o d e l r i n ) .  Since t h e r e are seven d i s t i n c t only f i v e  lines  i n the spectrum,  lapped carbon resonances. line  at  1 1 9 . 0 ppm s u g g e s t s  both protonated.  This  line  nated carbons which are is  shifted  slightly  to  c a r b o n atoms i n t h e m o l e c u l e  two o f  For example,  the l i n e s the  contributions is  intensity  represent  and w i d t h o f  f r o m two t y p e s o f  a s c r i b e d t o C-4 a n d C - 7 ,  i n t h e most s i m i l a r lower  likely  the  environments.  f i e l d because i t  is  but  closer  overthe  carbon atoms, two  proto-  Perhaps  to the  C-4  carbonyl.  - 64 -  C-3 i s  the protonated carbon nearest  to  t h e c a r b o n y l and i s  thus  a s s i g n e d t o t h e s i g n a l a t 1 3 2 . 2 ppm. Of t h e n o n - p r o t o n a t e d c a r b o n s , to  the resonance a t  ward.  lowest  field  The c a r b o n y l e x p e r i e n c e s  c a r b o n atoms i n t h e m o l e c u l e .  the assignment o f  ( 1 9 2 . 8 ppm)  the greatest It  is  is  t h e most s t r a i g h t  also the s i g n a l  different  of  The c a r b o n y l s i g n a l  and i s  the lowest  of p-butoxybenzoic  f i e l d resonance  the  intensity.  o f PEEK, w h i l e  nuclei.  s u p p o r t e d b y t h e CP/MAS s p e c t r a o f m o d e l c o m p o u n d s , acids.  least  atom for-  d e s h i e l d i n g o f any o f  T h e r e i s b u t one c a r b o n y l a t o m p e r r e p e a t i n g u n i t a r e two o f each o t h e r m a g n e t i c a l l y  the carbonyl  there  This assignment  is  p-alkoxybenozic  a c i d a p p e a r s a t 1 7 3 . 6 ppm  i n the alkoxybenzoic  acid  spectrum  (65). The m o d e l compounds a r e a l s o o f h e l p remaining carbons:  C-2,  i n the assignment o f  C-5 a n d C-6 t o t h e l i n e s  at  1 3 2 . 2 ppm, 1 5 0 . 8 ppm  a n d 1 5 9 . 3 ppm. C-5 a n d C-6 a r e a t t a c h e d t o t h e e t h e r expected to resonate at higher nance i s  ascribed to  the s i g n a l a t  agrees w i t h the p a r a l l e l (65).  Finally,  ether  links  carbonyl,  a n d t h e C-5 i s  t h e C-6 r e s o n a n c e to  than C-2.  link  Thus,  1 3 2 . 2 ppm. A g a i n ,  assignment o f  by n o t i n g t h a t  1 5 9 . 3 ppm a n d C - 5 ,  frequency  and t h u s t h e C-2  this  the p-alkoxybenzoic  t h e c a r b o n C-6  is  reso-  acid  spectra  i n a r i n g f l a n k e d by  assigned to the lower  field  and t o  signal  w i t h t h a t made b y W h i t a k e r of  differing  two the  at  t h e 1 5 0 . 8 ppm s i g n a l .  The a b o v e a s s i g n m e n t o f t h e CP/MAS s p e c t r u m o f PEEK d o e s n o t  tions  are  assignment  i n t h e r i n g a t t a c h e d t o one e t h e r is  the  et  al.  (24).  Nevertheless,  the peak p o s i -  t h e p u b l i s h e d s p e c t r u m a r e t h e same as i n t h i s w o r k . assumption i s  i n t h e number o f m a g n e t i c a l l y  agree  The  inequivalent  first car-  - 65 -  bons; Whitaker et a l . are  identical  Variable  assume t h a t  t o C-5 a n d C - 4 .  contact  there are only f i v e ,  Table 4 . 1 displays  that  t h e two  t i m e e x p e r i m e n t s were used by w h i t a k e r  assignments. et a l .  t i n g u i s h p r o t o n a t e d and n o n - p r o t o n a t e d c a r b o n atoms, b u t were n o t  C-6 a n d C-7  to  these  spectra  published.  Table 4.1:  Spectral Assignmment f o r PEEK: Comparison of Present Vork with Whitaker et a l . ( 2 4 ) (ppm r e l a t i v e to TMS).  Line Position (ppm)  Assignment  Line P o s i t i o n (ppm)  Assignment*  3  192.8  1  193.5  1  159.3  6  160.0  5,6  150.8  5  151.0  2  132.2  2,3  133.0  4,7  119.0  4,7  118.5  3  from reference  Just line,  dis-  24.  as t h e s p e c t r u m o f a m o r p h o u s PPS i s w i d e r  so t h e a m o r p h o u s PEEK s p e c t r u m i s w i d e r  F i g u r e 4 . 1 1 shows s p e c t r a o f  than the  than the  crystalline.  t h e amorphous and c r y s t a l l i n e  PEEK s a m p l e s  w h i c h w e r e o b t a i n e d u n d e r t h e same c o n d i t i o n s .  The d i f f e r e n c e  i s n o t as p r o n o u n c e d f o r  is not  the f r a c t i o n a l  PEEK as f o r  crystallinity  PPS. T h i s  o f PEEK i s  less  than t h a t  crystal-  in  surprising  widths because  o f PPS (40% v e r -  - 66 -  sus 65%). T a b l e 4 . 2 amorphous  Line  the h a l f height widths  for  the c r y s t a l l i n e  and  spectra.  Figure 4 . 1 1 :  Table 4 . 2 :  lists  ( a ) The s o l i d s t a t e CP/MAS s p e c t r u m o f a m o r p h o u s PEEK. ( b ) The s o l i d s t a t e CP/MAS s p e c t r u m o f c r y s t a l l i n e PEEK.  Spectral  Position (ppm)  linewidths  Assignment  for  crystalline  Crystalline Linewidth (ppm)  a n d a m o r p h o u s PEEK  Amorphous Linewidth (ppm)  192.8  1  21  39  159.3  6  20  45  150.8  5  20  66  132.2  2,3  26  53  119.0  4,7  26  103  Figure 4.12:  Variable contact time CP/MAS spectra of c r y s t a l l i n e PEEK. (* denotes the signal due to d e l r i n ) .  - 68 -  I n the v a r i a b l e  contact  n u c l e i appear w i t h g r e a t e r cross-polarization presents  times  requires  PEEK. E v e n a t as s h o r t are apparent.  i n order  shorter  able contact  a contact  of  signal  of  experiment  t i m e as 0 . 0 1 ms,  t o make f a i r  the c r y s t a l l i n e  identical  the r e l a t i v e  longer carbonyl to  1 ms was a  suit-  performed. conditions the  a comparison between  i n the second s e t ,  acquisition  atten-  conditions. against  the  C-5 a n d C-6 a n d f o r  contact  the  combined  t h e p r o t o n a t e d c a r b o n s C-3 a n d C-4 a r e g i v e n i n A p p e n d i x  from the spectra of Figure 4.12,  the optimum c o n t a c t  the  a n d a m o r p h o u s f o r m s o f PEEK t h e  peak i n t e n s i t y  quaternary carbons,  be m e a s u r e d . However,  ernary  the  served  Due t o a n o v e r l a p w i t h a s p i n n i n g s i d e b a n d t h e c a r b o n y l s i g n a l  that  4.12  on t h e Hartmann-Hahn m a t c h i n g o f  I n order  t i o n was p a i d t o m a i n t a i n i n g  the single  time  This experiment  e x p e r i m e n t s were d u p l i c a t e d and p a r t i c u l a r l y  of  Figure  dependent upon t h e o p e r a t i n g  particularly  time r e s u l t s  because  The q u a t e r n a r y c a r b o n s r e q u i r e  time of a l l .  time i s  p r o t o n and carbon f i e l d s .  time f o r  contact  t h e o t h e r CP/MAS e x p e r i m e n t s  The o p t i m u m c o n t a c t the spectrometer,  times  i s more e f f e c t i v e .  assignment and t o a s c e r t a i n t h a t  time f o r  Log-log plots  contact  carbon  t o d e v e l o p maximum m a g n e t i z a t i o n a n d t h e  the longest contact  confirm the spectral  contact  at  o f p r o t o n a t e d carbons  protonated signals  of  intensity  the protonated  a s e l e c t i o n of spectra from a v a r i a b l e  on c r y s t a l l i n e  contact  time experiment,  it  is  t i m e o f t h e c a r b o n y l exceeds t h a t  of  II.  could  not  concluded the  quat-  carbons.  The s c a t t e r long experimental  of the data points  is  time of twenty hours,  c o n d i t i o n does n o t r e m a i n c o n s t a n t  due t o t w o m a i n f a c t o r s : during which the  and ( i i )  (i)  the  Hartmann-Hahn  the d i f f i c u l t y  in  obtaining  - 69 a good baseline i n the noisy spectra from which to measure the peak heights (the number of scans was l i m i t e d by the length of the experiment) . The data points were f i t a r b i t r a r i l y to a q u i n t i c polynomial. The contact time p r o f i l e s f o r two signals of the amorphous PEEK sample are p l o t t e d i n Figure 4.13. The C-3 and C-4 protonated carbon  z LU r—  Z  .  LU  O  -3.0  -2.0  -1.0  LN OF CONTACT T I M E Figure 4.13:  0.0 [LN  1.0 MSEC]  Variable contact time plots f o r amorphous PEEK: ID C-3, C-4 protonated carbons. A C-6 non-protonated carbon.  magnetization i s seen to reach maximum i n t e n s i t y quickly r e l a t i v e to the quaternary carbon, C-6. A s i m i l i a r trend i s noted i n the spectra of the c r y s t a l l i n e sample. Figure 4.14 compares the contact time p l o t s of the C-5 carbon i n the c r y s t a l l i n e and amorphous samples. The C-5 signal of the c r y s t a l l i n e has the longer optimum contact time.  - 70 0.5  -3.0  -2.0  -1.0  0.0  LN" OF CONTACT T I M E Figure 4.14:  [LN  1.0 MSEC]  Variable contact time plots f o r C-5, non-protonated carbon of PEEK: A amorphous Q crystalline  The r e s u l t s of these experiments indicate that the optimum contact time of protonated carbons i s less than that of non-protonated and that the amorphous form has a s l i g h t l y shorter optimum contact time than the c r y s t a l l i n e . Table 4 . 3  summarizes these findings.  Again, these r e s u l t s are somewhat contrary to expectation since the dipolar interactions which promote e f f i c i e n t c r o s s - p o l a r i z a t i o n are l i k e l y to be stronger i n the c r y s t a l l i n e material because the c r y s t a l l i n e PEEK i s both more r i g i d and more dense than the amorphous. However, as previously mentioned with respect to PPS, the c r o s s - p o l a r i z a t i o n  - 71 -  Table 4 . 3 :  Optimum C o n t a c t Time R e s u l t s PEEK.  Crystalline opt. contact time [msec]  Nucleus  C-3,  f o r Amorphous a n d  C-4  Amorphous opt. contact time [msec]  1.3  0.8  C-5  2.3  1.5  C-6  1.7  1.6  rates  a r e dependent upon the s p i n - l a t t i c e  protons  i n the r o t a t i n g frame.  Crystalline  r e l a x a t i o n times o f  The i n c r e a s e d m o l e c u l a r m o t i o n i n t h e  a m o r p h o u s m a t e r i a l may c a u s e a s h o r t e r  T-^p v a l u e a n d t h u s b e  for  contact  4.5  the  the decreased ^ C s i g n a l a t longer 3  times  responsible  (63).  SUMMARY AND CONCLUSION OF CP/MAS WORK  The h i g h r e s o l u t i o n  li  C  s p e c t r a f o r PEEK a n d PPS i n c r y s t a l l i n e  amorphous f o r m s have b e e n o b t a i n e d .  The a s s i g n m e n t o f t h e s p e c t r u m  e a c h p o l y m e r was made w i t h t h e a i d o f t h e d i p o l a r  dephasing  and of  technique,  PEEK h a v i n g t h e m o r e c o m p l i c a t e d a s s i g n m e n t o f t h e t w o . A comparison o f the c r y s t a l l i n e b o t h cases t h e l a t t e r amorphous l i n e  a n d a m o r p h o u s s p e c t r a shows t h a t  i s considerably broadened;  Is generally  a broadening of  observed f o r s e m i - c r y s t a l l i n e  The s p e c t r a o f PPS h a v i n g i n t e r m e d i a t e  in  the  polymers.  crystallinities  suggest  the  - 72 -  s u p e r p o s i t i o n o f amorphous and c r y s t a l l i n e l i n e - s h a p e s . T h i s i n d i c a t e s t h a t f u r t h e r s t u d i e s o f v a r y i n g c r y s t a l l i n i t i e s e m p l o y i n g s p e c t r a l subt r a c t i o n and l i n e c o n v o l u t i o n would be i n f o r m a t i v e . A l s o , v a r i o u s sequence t e c h n i q u e s  may be used t o i n d i c a t e t h e s e p a r a t e  pulse  components: ( i )  D e c h t e r (63) showed t h a t , i n p o l y e t h y l e n e o x i d e , s p e c t r a o f l o n g r e l a x a t i o n times a r e p r i n c i p a l l y o f c r y s t a l l i n e c h a r a c t e r , ( i i ) H a r r i s and coworkers (66) i n d i c a t e d t h a t a p r e - c o n t a c t t i m e h a d a s i m i l i a r i n polyethylene n/2-r-n/2  effect  t e r e p h t h a l a t e and ( i i i ) F y f e e t a l . (64) u s e d a  sequence f o r p o l y e t h y l e n e w h i c h , a t s h o r t r , y i e l d e d s p e c t r a  of predominantly  amorphous l i n e - s h a p e .  The v a r i a b l e c o n t a c t time e x p e r i m e n t s on PEEK i n d i c a t e d s t r o n g e r d i p o l a r couplings f o r the protonated  than f o r the non-protonated car-  bons . The s h o r t e r optimum c o n t a c t time f o r t h e amorphous PEEK i s e x p l a i n e d as b e i n g due t o t h e f a s t e r r o t a t i n g frame r e l a x a t i o n r a t h e r than t o stronger d i p o l a r i n t e r a c t i o n s . A f u l l Ti  p  r e l a x a t i o n study i s a p r e r e q u i s i t e f o r the i n t e r p r e t a t i o n  o f o t h e r CP/MAS e x p e r i m e n t s .  R e l a x a t i o n s t u d i e s o f C n u c l e i and v a r i 1 3  a b l e t e m p e r a t u r e CP/MAS may a l s o y i e l d i n f o r m a t i v e r e s u l t s .  - 73 -  5.  5.1  WIDE-LINE PROTON NMR STUDIES  INTRODUCTION TO SOLID STATE PROTON NMR  One o f  the e a r l i e s t  studies  of semi-crystalline  l i n e p r o t o n NMR was made b y Pake a n d W i l s o n i n 1953 was a n a t t e m p t  to establish c r y s t a l l i n i t i e s  tetrafluoroethylene tunately,  (Teflon)  though t h e i r  too a r b i t r a r y  commercial  importance,  (62,68,75-78).  report  of  sulfide)  polyethylene  I n the c u r r e n t  literature,  ether ketone),  (68-74)  those o f  major  and p o l y p r o -  t h e r e h a s b e e n no  a n d b u t one  of  from other or  (ii)  o f macromolecules  techniques  to gain exclusive  s o l i d s t a t e p r o t o n NMR s t u d i e s : s e c o n d moment o r  (i)  are  s u c h as d i e l e c t r i c  e x c e p t b y NMR. T h e r e a r e e s s e n t i a l l y  (ii)  used  (32).  spectroscopies  and T 2 ) ,  pioneers;  thermoplastics.  in particular,  t o complement t h e f i n d i n g s  (T]_, T ^ _ ,  simply  crystallinity  Pake a n d W i l s o n w e r e  The g o a l s o f w i d e - l i n e p r o t o n NMR s t u d i e s  t h e use o f  Unfor-  S i n c e t h e 1 9 5 0 ' s many o t h e r r e s e a r c h e r s h a v e  ^H NMR o f p o l y ( e t h e r  not obtainable  and p o l y -  t h e a n a l y s i s was  s t u d i e d have p r i m a r i l y been c o n f i n e d t o  pylene  mechanical  work  analysis.  d i d not c o r r e l a t e w i t h the  NMR i n t h e s t u d y o f s e m i - c r y s t a l l i n e  poly(phenylene  wide-  t o u n d e r t a k e a p r o b l e m o f g r e a t magnitude w h i c h has  n o t y e t been r e s o l v e d .  The p o l y m e r s  Their  of polyethylene  p r i n c i p l e was c o r r e c t ,  d e t e r m i n a t i o n s b y o t h e r methods. However,  wide-line  (67).  b y means o f NMR l i n e - s h a p e  and t h e r e s u l t s  t h e y were t h e f i r s t  polymers by  or  information which t h r e e approaches  relaxation  linewidth  (i)  studies  is to  measurements, and  (iii)  - 74 -  line-shape  analysis.  f o r m e d as f u n c t i o n s the  three  These e x p e r i m e n t s of  functions  o f s o l i d s t a t e PMR a r e t o g i v e  ated the spectra i n t o intensities  polymer c r y s t a l l i n i t y is  the nature  of  two, of  polymers,  line-shape  (67,69,71,72).  One o f  t h e most n o t a b l e  (72).  The s p e c t r a l  line.  Gauss-Lorentz product  the c r y s t a l l i n e  regions  the a r b i t r a r y nature  t i o n of  the line-shape w i t h  Relaxation studies molecular motions  of  the  are  Lorentzian  The b r o a d  two c u r v e s  line  indicate  th  analysis  a n d s e c o n d moment m e a s u r e m e n t s r e f l e c t  varia  the  The t y p e o f e x p e r i m e n t a n d t h e mag-  the frequency of the detected  information from other  techniques, (32).  r e l a x a t i o n t i m e s t u d i e s may p r o v i d e  inhomogeneity of the polymer.  motions.  for molecular  t h e m o t i o n s can o c c a s i o n a l l y be s u r m i s e d  about the s p a t i a l  successes  lines  Problems w i t h t h i s  can y i e l d a c t i v a t i o n energies  polymers,  the  of  t h e d e c o n v o l u t i o n p r o c e s s and t h e  i n the polymer.  a n d , when c o m b i n e d w i t h  separ-  temperature.  s t r e n g t h determine  Relaxation studies  t i o n of  and t h e o t h e r  two t y p e s o f amorphous p h a s e .  include  crystalline  of  t h e components has y i e l d e d an e s t i m a t e  and a medium-width,  origin of  the  Correlation of  line;  field  into  a n a l y s i s has  a narrow,  netic  o  The m o s t  the motions  p r e s e n t e d as t h e sum o f a b r o a d , G a u s s i a n l i n e ;  presence o f  The r e s u l t s  insight  t h r e e o r more c o m p o n e n t s .  t h e w o r k o f Bergmann on p o l y e t h y l e n e  represents  per-  chains.  I n some s e m i - c r y s t a l l i n e  relative  they are  a r e v e r y much i n t e r c o n n e c t e d .  p o l y m e r morphology and t o d e t e r m i n e macromolecular  if  t e m p e r a t u r e o r sample p r e p a r a t i o n .  types of experiments  important  a r e most u s e f u l  the  In  exact  semi-  information  For example,  t w o o r m o r e T i ^ t i m e s b u t o n l y one T^ t i m e  motions  indicates  the spin  detec-  - 75 -  diffusion estimate  i n the system; the size of  the presence o f  the d i f f e r e n t  t h i s phenomenon c a n b e u s e d  crystalline  and amorphous  to  regions  (68,74).  5.2  SOLID STATE PROTON NMR THEORY  5.2.1  L i n e - S h a p e s o f S o l i d S t a t e PMR S p e c t r a  The s p i n H a m i l t o n i a n f o r that  a proton i n a strong magnetic  expressed i n equation 4 . 1 . Like  nuclear  spin of  1/2,  but unlike  nucleus,  is  of  The h o m o n u c l e a r  t h e abundant hydrogen n u c l e i Q  I n the s o l i d s t a t e ,  f i e l d s vary w i t h the p o s i t i o n of  the broad l i n e s which are c h a r a c t e r i s t i c Although the d i p o l a r  of  interaction  and t h i s v a r i a t i o n  local produces  the s o l i d s t a t e p r o t o n  protons,  Gaussian d i s t r i b u t i o n  the d i p o l a r o f resonance  The i n t e r a c t i o n o f homonuclear  i n t e r a c t i o n g e n e r a l l y produces  of a  frequencies.  t w o m a g n e t i c moments  dipole-dipole  spec-  dependent  i n s a m p l e s w h i c h a r e n o t o r i e n t e d a n d / o r w h i c h c o n t a i n a number inequivalent  the  fields  these  Is d i r e c t i o n a l l y  100%  dipolar  to local  the magnitude o f  the n u c l e i  that  The s t r o n g  give r i s e  is  coupling expression  (/*]_, 1 * 2 ) (79):  *-  s  a  dipolar  so much s o ,  i n t h e e q u a t i o n may b e n e g l e c t e d .  which supplement H .  troscopy.  t h e ^H n u c l e u s  the dominant term i n the e q u a t i o n ,  subsequent terms interactions  ratio.  is  t h e p r o t o n has  3  the  abundant and has a l a r g e g y r o m a g n e t i c interaction  the 1 C nucleus,  field  g i v e n by  the  - 76 -  w  where r ^ 2 i-  s  t  n  12  ~  r  "  [ /*l'A*2 "  5  r 2  interdipole  e  c o n s i d e r e d more s i m p l y  distance.  2  is  (Ml-ri2)(A*2* 12>]  < - )  r  5  Equation 5 . 1 can a l s o  be  =  12  -/i -H 2  (5.2)  1 2  t h e f i e l d p r o d u c e d b y s p i n 1 a t s p i n 2 . The w i d t h o f  Gaussian l i n e  is  1  as:  W  where H ^  3  dependent upon the s t r e n g t h o f the d i p o l a r  the  interac-  tions . The t w o c o n v e n t i o n a l ways o f c o n v e y i n g t h e b r o a d n e s s o f  the  a r e b y l i n e w i d t h m e a s u r e m e n t s a n d b y s e c o n d moment c a l c u l a t i o n s . linewidth  is  simply the w i d t h o f the s p e c t r a l  usually  given i n units  moment,  S2, is  of  line  at half  frequency or o f magnetic  calculated  field.  line The  height, The  second  by:  J  r°  7 (W-WQ)^  (w)d«  -CO  S  -  2  (5.3) f°  -00  where f ( w )  is  frequency of  the  f(w)d»  f u n c t i o n of the lineshape  the n u c l e i  and w  i n the e x t e r n a l magnetic  is  D  the angular  field.  Larmor  Alternatively,  t h e s e c o n d moment may be d e t e r m i n e d f r o m t h e F I D w h i c h may be  expressed  as: f(t)  -  Mo(l  - S t /2! 2  2  + S t /4! 4  4  - S t /6! 6  6  +  ...)  (5.4)  - 77 w h e r e S 2 , S 4 , a n d Sg a r e t h e s e c o n d , line.  The h a l f  height  linewidth,  a p u r e l y Gaussian l i n e  1  distance.  dipolar  coupling  generally  Another  rangement presence  2  occurs  is  at very  In this  s  l  the S 2 , for  expression:  o  8  )  2  1  /  ( - )  2  5  the  line  is  the  In a solid,  lattice  is  ( S 2 ) l /  r » l ,  2  where r  c  the average  Conversely,  time  lines  atomic  have the rear-  at high temperatures,  m o t i o n causes complete  c o u p l i n g and s p e c t r a l  for  the  rigid.  is  c  exhibit  averaging of  extreme  5  inter-  l o w t e m p e r a t u r e s when t h e m o t i o n s  situation,  random i s o t r o p i c  2  s e c o n d moment,  s t r o n g e s t when t h e  time which characterizes  dipole-dipole  2 <  * the  is molecular motion.  about a given nucleus. of  a r K  the w i d t h o f  factor  interaction  been " f r o z e n o u t " . correlation  -  2  which determines  dipolar  This  <AH>iy2  are r e l a t e d by the  <AH> /  One f a c t o r  f o u r t h a n d s i x t h moments o f  the  the  narrowing.  Here, ( S 2 ) 1/2, c  « l  and t h e c o r r e l a t i o n  however,  an i n t e r m e d i a t e  spectral  line  retains  n a r r o w e d due t o the  lattice.  of molecular  5.2.2  region i n which  much o f  its  the weakening o f  The e x t e n t  time  of  motion w i t h i n  is very  Gaussian c h a r a c t e r b u t the d i p o l a r  There  In this  ( S 2 )  is  is,  case,  insight  into  the  somewhat  i n t e r a c t i o n by motion  the narrowing gives the  short.  the  in  degree  polymer.  Relaxation  There are  three  types  of relaxation  times  referred  to  in this  work:  - 78 -  (i)  spin-lattice  (iii)  relaxation,  spin-lattice  relaxation,  The o t h e r  Spin-Lattice  A nucleus of energy s t a t e s :  The r a t i o  of  s p i n 1/2  net magnitude o f  the magnetization  adjust  energy spins  to  t h e same number o f s p i n s However,  after  particular  field  s t r e n g t h and t e m p e r a t u r e  the readjustment  of  I n order  for it  is  a nucleus  lower  state,  ings,  c a l l e d the l a t t i c e .  i n the sample.  At  the spin popula-  the spin of  energy  level  populations  spin states  achieved.  the spin population i s not  t h e phenomenon o f s p i n - l a t t i c e  to  field,  and t h e e q u i l i b r i u m Boltzman d i s t r i b u t i o n  The  due  are i n the h i g h e r  some t i m e ,  is  between  the temperature.  i n d u c e d w i t h i n t h e sample i s  a magnetic  there  lower energy spins  a n d t o t h e number o f s p i n s  a sample i s p l a c e d i n t o  If  apparent.  the energy d i f f e r e n c e  t h e Boltzman c o n s t a n t and T,  the p o p u l a t i o n d i f f e r e n c e  as a r e i n t h e l o w e r .  some  possible  the f i e l d .  a B o l t z m a n p o p u l a t i o n d i s t r i b u t i o n becomes  t o e x p ( - A E / k T ) , w h e r e AE i s  are even,  discussed i n  f i e l d has two  the spin w i t h or against  k,  tions  is  Spin-lattice  defined.  placed i n a magnetic  the spin s t a t e s ,  the i n s t a n t  study,  Ti^.  and  T2,  Relaxation  t h e number o f h i g h e r  proportional  to this  t w o a r e more b r i e f l y  alignment of  a r e many n u c l e i ,  spin-spin relaxation,  r e l a x a t i o n i n the r o t a t i n g frame,  w h i c h i s most p e r t i n e n t  d e t a i l below.  5.2.2a  T]_, ( i i )  for  The r e a s o n  immediate  is  the  that  explained  relaxation.  i n the higher  spin state  m u s t g i v e up a q u a n t u m o f e n e r g y , This energy t r a n s f e r  to  'relax'  AE, t o  process  the  to  the  surround-  requires  stimu-  by  - 79  lated emission, Larmor the  that  is,  t h e r e m u s t b e some r e l a x a t i o n m e c h a n i s m a t  frequency which can absorb  system r e a d j u s t s  availablity  of  I n order nucleus,  t h e AE o f e n e r g y .  to equilibrium magnetization  r e l a x a t i o n mechanisms t o be a s u i t a b l e  at  fluctuating  fields  of  f r o m an u n p a i r e d e l e c t r o n ,  a particularly  effective  The s p i n l a t t i c e  dM  the  1/2  its  the nucleus. motions  interactions.  Such  i n the  The f i e l d  solid  fluctu-  ( s u c h as f o u n d i n p a r a m a g n e t i c  relaxation  relaxation  which  a spin  one a n d  of  from the various  the d i p o l a r  the  frequency.  magnetic  t h e Larmor f r e q u e n c y  at  a measure o f  r e l a x a t i o n mechanism f o r  arise primarily  w h i c h cause f l u c t u a t i o n s  The r a t e  is  t h e Larmor  t h e f i e l d m u s t be a t i m e - v a r y i n g ,  f r e q u e n c y must c o r r e s p o n d t o  ations  -  O2),  is  mechanism.  time  is  defined  (M  z  z  -  as  M ) D  (5.6) dt  where M and M  0  z  is  is  the net magnetization of  the magnetization at  ing s p i n system, the e q u i l i b r i u m  at  large  the r e l a x i n g  r , (equilibrium).  Thus,  time  in a  t,  relax1/e  of  magnetization.  the most s t r a i g h t  different  forward of  techniques these  method w h i c h employs a 1 8 0 ° - T - 9 0 ° p u l s e the magnetization along the z a x i s . magnetization p a r t i a l l y magnetization  s p i n system a t  a t i m e T]_, t h e m a g n e t i z a t i o n h a s r e c o v e r e d t o  T h e r e a r e a number o f One o f  Tl  into  recovers,  the xy plane  to  is  used f o r  the  inversion  sequence.  allow  final for  its  time  pulse of  90°  detection.  T^.  recovery  The 1 8 0 ° p u l s e  During the w a i t i n g  and t h e  measuring  r,  inverts  the  tips The  the  recycle  - 80 -  t i m e between sequences  is  typically  5 times the s p i n - l a t t i c e  relaxation  time. Figure  Figure  5.1:  5 . 1 shows a s c h e m a t i c r e p r e s e n t a t i o n o f t h e e x p e r i m e n t .  The  (a) A schematic r e p r e s e n t a t i o n o f the i n v e r s i o n recovery sequence f o r s p i n - l a t t i c e r e l a x a t i o n t i m e measurements (T >T >r ). 3  2  x  ( b ) The c o r r e s p o n d i n g  magnetizaton i s  spectra.  r e l a t e d t o t h e T^ v a l u e as shown i n e q u a t i o n  5.7:  M(r) M  0  1 - 2exp  (-r/Ti)  (5.7)  - 81 -  where M ( r ) against  is  the magnetization at  r gives  a line  Spin d i f f u s i o n relaxation  times  of slope  is  this  o n l y one i s  The f i r s t  t h e T^ r e l a x a t i o n , time.  to material  relaxation times.  is  trivial,  process  diffusion.)  of  5.2.2b  Spin-Spin  all  it  is,  is  often  reasons  t h e T^s a r e  spin-lattice  Usually,  a  finite  transitions.  to thermal conduction  strong dipole-dipole  spins relax  During  energy can propagate  energy-conserving  The f i n a l  result  a t t h e same  for  coinciden-  i n the s p i n system f o r  i s more a n a l o g o u s  couplings of  the  than  maintain  energy  rate.  Relaxation  Spin-spin relaxation precessing magnetization  is  the l a t t i c e  the primary  i n the xy plane  t i o n s between the n u c l e a r energy to  that  "flip-flop"  the communication between the s p i n s . that  However,  of  system  the presence o f s p i n d i f f u s i o n .  Within this period,  this  propagation is  ln[1-M(r)/Mo]  There a r e two p o s s i b l e  s p i n energy remains  between n u c l e i by a s e r i e s ( I n a sense,  of  1/Tj_.  observed.  t h e same. The s e c o n d i s  period of  a plot  i n two component s y s t e m s . A two component  phenomenon.  tally  Thus,  a n i m p o r t a n t phenomenon i n t h e c o n s i d e r a t i o n  n a t u r a l l y has two s p i n - l a t t i c e t h e case t h a t  t i m e r.  factor (Figure  i n t h e decay o f 5.2).  Direct  spins promote r e l a x a t i o n w i t h o u t  the  interac-  loss  of  s y s t e m . The a c t u a l d e c a y o f t h e m a g n e t i z a t i o n  in  * the xy plane  (T2)  relaxation time, field  depends upon t h r e e (ii)  inhomogeniety,  factors  (80):  (i)  t h e s p i n - s p i n r e l a x a t i o n and ( i i i ) 7AH . Q  the the  spin-lattice magnetic  - 82 -  VT * -  l  2  I n the s o l i d s t a t e ,  X  T^»T . 2  is  is  + VT + 2  field,  t h e case t h a t  represents  time at which the free  t,  Figure  5.2:  is  to set T  2  (Figure  2  5.3).  given a f a i r l y  *  1/T  t,  3  (5.8)  0  2  « 1/T . 2  i n d u c t i o n decay i s  Thus, 1/e  the spin-spin  An a l t e r n a t e  convention for  maximum.  It  t o n o t e t h a t because t h e T  width of  the spectrum i n the frequency domain,  s e c o n d moment d a t a p r o v i d e  of  T  2  its  relaxation  1  any c u r v e  as t h e t i m e a t w h i c h t h e m a g n e t i z a t i o n d e c a y i s i s necessary  homoge-  t,  A schematic r e p r e s e n t a t i o n of effect ( t > t > t ) .  maximum v a l u e  7AH  As a r e s u l t ,  neous m a g n e t i c the  it  /2T  similar  information.  2  1/e  determines  type of  the  spin-spin relaxation  the line and  - 83 -  — T — 2  Figure  5.2.2c  5.3:  T , for  spin-spin r e l a x a t i o n time, is the time required t h e FID t o decay t o 1/e o f t h e o r i g i n a l v a l u e .  2  Spin-Lattice  Relaxation  The s p i n - l a t t i c e essentially yields  i n the Rotating  relaxation  i n the r o t a t i n g frame experiment  t h e same as t h e n o r m a l T^ e x p e r i m e n t .  D  field,  typically  of  is  is  measurement  the Larmor  frequency  t h e o r d e r o f MHz. The f o r m e r r e s p o n d s  m o t i o n a t much s l o w e r f r e q u e n c i e s ,  of  the order  frame r e l a x a t i o n t i m e ,  Tip,  magnetization which i s  locked to a radio  o f k H z . The  the c h a r a c t e r i s t i c  rotating  decay time o f  frequency  field  to  i n the  the  spin  rotating  plane.  5.2.2d  The D e p e n d e n c e o f R e l a x a t i o n o n  Figure for  The l a t t e r  i n f o r m a t i o n on t h e r e l a x a t i o n mechanisms o f  of the H  xy  Frame  5.4  sketches  a theoretical  Temperature  t h e d e p e n d e n c e o f T]_, T  p o l y m e r h a v i n g two t r a n s i t i o n s .  l p  and T  on  temperature  T^ a n d T j -  show m i n i m a  2  - 84 at  that  temperature  the n u c l e i  i n the f i e l d H  temperature of strength.  at which Q  wr -l, c  (w i s  o r H]^ a n d r  c  is  t h e minimum r e l a x a t i o n t i m e  Higher  fields  the resonance frequency the c o r r e l a t i o n is  time).  thus a f u n c t i o n o f  show m i n i m a a t h i g h e r  of The field  temperatures.  T Figure  5.4:  The t h e o r e t i c a l (30).  The t r a n s i t i o n as t h o s e o f T ^ kHz tive  (30).  d e p e n d e n c e o f Tj_, T j . a n d T£ o n  temperatures  of T 2  t e n d t o be a p p r o x i m a t e l y  and b o t h respond t o m o t i o n s  The b e h a v i o u r  of T 2 ,  o f decreased s p e c t r a l  temperature  with respect  l i n e w i d t h due t o  the  i n the range o f  10 t o  to  is  temperature,  increased motion  same  100  indicawith  temperature. An e s t i m a t e  of  t h e a c t i v a t i o n e n e r g y may b e o b t a i n e d b y  t h e r e l a x a t i o n d a t a as t h e l o g o f r e l a x a t i o n temperature, ing that  as s k e t c h e d i n F i g u r e  the c o r r e l a t i o n  5.5  (for  time against a single  plotting  the  inverse  transition).  t i m e may be e x p r e s s e d as a n A r r h e n i u s  of  Assum-  process:  - 85 -  r  then the slope o f - A E / R a n d AE/R  Figure  5.5:  c  the l i n e a r  -  r  Q  exp (AE/RT)  portions  of the p l o t  '  (5.9)  i n Figure  5.5  are  respectively.  The t h e o r e t i c a l d e p e n d e n c e o f temperature (80).  log T^,  T^  w  and T  2  on  Inverse  -  5.3  -  EXPERIMENTAL  The b r o a d - l i n e power  NMR m e a s u r e m e n t s w e r e made w i t h a B r u k e r  Fourier-transform  The B r u k e r  software  block  of  size  transients the  86  2K,  spectrometer  programme,  the  operating at  DISCXP was u s e d .  The s p e c t r o m e t e r  s i g n a l was r e c e i v e d o n o r v e r y c l o s e  to minimize  the  signal  i n the  The T ^ m e a s u r e m e n t s (180-T-90). least  The r e c y c l e  times  equal  The t e m p e r a t u r e device thermal  controlled gradient  imaginary  D a t a was c o l l e c t e d and t y p i c a l l y  conditions  to resonance,  time exceeded f i v e  to  temperature  across  to  a  16 t o  were s e t  such  32  that  a n d p h a s e d so  as  sequence  t i m e s Tj_, a n d s p e c t r a  times were o b t a i n e d p e r the recycle  in  channel.  sample,  for  with  two  at or  time.  range extended from ambient  the  protons.  employed an i n v e r s i o n r e c o v e r y p u l s e  10 w e l l - s p a c e d d e l a y  more d e l a y  200 MHz f o r  sweep w i d t h was 5 0 0 , 0 0 0 H z ,  were averaged.  CXP h i g h  an accuracy  t h e sample o f ±1°C  t o 440K. An a i r  flow  of ±0.5°C,  a  (manufacturer's  with  specifica-  tions) . D a t a was t r a n s f e r r e d data s t a t i o n time  of  the  three points Fourier  for  plotting  spectrometer of  from the Bruker  system t o  and p r o c e s s i n g .  Because t h e r e c e i v e r  was =*8;us I t  t h e FID b e f o r e  transformation  was n e c e s s a r y  application  into  orientation.  small  to  delete  the b a s e l i n e  NIC-1280 recovery  the  first  correct  and  routines.  The s a m p l e s w e r e p a c k e d i n 10 mm g l a s s was c u t  of  a Nicolet  (lxlmm)  pieces  tubes.  The a m o r p h o u s  a n d p a c k e d so a s t o  ensure  film  random  -  5.4  87  -  RESULTS  5.4.1  Line-Shape  Results  W i t h one e x c e p t i o n , from the r e l a x a t i o n  the  fully  relaxed spectra  (those having  t i m e e x p e r i m e n t s were used f o r  the line-shape  The e x c e p t i o n was t h e c a s e o f one s e t o f c r y s t a l l i n e 2),  PPS d a t a ,  w h e r e a s i m p l e J T / 2 p u l s e was u s e d t o o b t a i n t h e F I D .  obtained for ambient  amorphous and c r y s t a l l i n e  temperature  At ambient lines  to  linewidths  temperature,  all  s p e c t r a a p p e a r e d as b r o a d  for  are presented i n Table line material  the approximate  T h e s e s p e c t r a a r e shown i n F i g u r e  ( i n kHz)  the  f o u r polymer  than those o f  the c r y s t a l l i n e  5.6.  samples a t  5 . 1 . I n both polymers,  are broader  tures below the Tg,  (series  Spectra  PPS a n d PEEK  study.  were  from  430K.  w i t h a s m a l l n a r r o w component a t  Gaussian l i n e .  samples o f  T>5TI),  the  Gaussian  centre The  of  t h e amorphous. A t  s p e c t r a show b r o a d e r  the  half-height  ambient  lines  of  temperature the  all lines  crystaltemperathan  the  amorphous.  Table  5.1:  Half Height Linewidths Ambient Temperature.  [kHz]  Crystalline  for  PEEK a n d PPS PMR S p e c t r a  Amorphous  PEEK  28.8  27.0  PPS  29.4  25.0  at  - 88 -  Figure 5 . 6 :  PMR spectra of (a) c r y s t a l l i n e PEEK; (b) amorphous PEEK; (c) c r y s t a l l i n e PPS; (d) amorphous PPS; a l l at ambient temperature.  - 89 The s p e c t r a l  linewidth  For a l l samples, increases; against  Tg,  the l i n e s narrow p r o g r e s s i v e l y  Figures  5 . 7 t o 5 . 1 0 show p l o t s  temperature.  different  is inversely proportional  (The two s e r i e s  of the width o f the broad  line  i n d i c a t e m e a s u r e m e n t s made a t  t h e l i n e w i d t h decreases approximately  conditions.)  linearly with  of the c r y s t a l l i n e  o f decrease w i t h temperature.  temperature.  as t h e t e m p e r a t u r e  times w i t h s l i g h t l y v a r i e d spectrometric  Above T g , t h e l i n e w i d t h s  to  polymers  Below  temperature.  show a g r e a t e r  Amorphous PEEK shows a n a b r u p t d r o p  rate  in  l i n e w i d t h b e t w e e n 420K a n d 4 3 0 K . The l i n e w i d t h o f t h e a m o r p h o u s PPS a l s o shows a s h a r p d e c r e a s e by an i n c r e a s e  in  i n t h e r e g i o n 360K t o 370K,  followed  immediately  linewidth.  PEEK a t a m b i e n t  temperatures presents  s i a n l i n e w i t h a s m a l l narrow component,  a s p e c t r u m o f a b r o a d Gaus-  less  t h a n 6% o f t h e  total  30.0  •  •  • •  • •  •  IS  A  •  a  lS.OL 290.0  Figure  5.7:  320.0  350.0 380.0 TEMPERATURE CK3  410.0  440.0  L i n e w i d t h v e r s u s t e m p e r a t u r e f o r •'-H s p e c t r a o f PEEK ( i n d u p l i c a t e ) .  crystalline  - 90 -  30.0  25.0  •  A  •  A  A  <t  •  20.0  •  • 15.0 290.0  Figure 5.8:  320.0  350.0 380.0 TEMPERATURE CK3  Linewidth versus temperature PEEK ( i n duplicate).  for  410.0  440.0  spectra of amorphous  30.0  290.0  Figure 5.9:  320.0  350.0 380.0 TEMPERATURE CK3  Linewidth versus temperature PPS ( i n duplicate).  for  410.0  440.0  spectra of c r y s t a l l i n e  - 91 30.0  r*j  •  a: 2 5 . 0  • •  IU  1$  •  20.0  •  15.0 290.0  320.0  350.0  a  380.0  TEMPERATURE Figure  5.10  intensity.  As t h e t e m p e r a t u r e increases  The a m o r p h o u s PEEK f o l l o w s Gaussian l i n e  rises,  440.0  CK]  Linewidth versus temperature f o r PPS ( i n d u p l i c a t e ) .  and t h e n a r r o w l i n e  all  410.0  spectra of  amorphous  t h e b r o a d l i n e becomes l e s s  in intensity  essentially  t o a b o u t 10% o f  t h e same p a t t e r n ,  i s n o t as w i d e a n d t h e n a r r o w c o m p o n e n t  the  broad  total.  though,  the  i s more i n t e n s e  at  temperatures. The e f f e c t  of  t e m p e r a t u r e on t h e l i n e - s h a p e  more p r o n o u n c e d t h a n f o r similar  PEEK. The s p e c t r a c o l l e c t e d b e l o w T g a r e  t o t h o s e o f PEEK, a l t h o u g h ,  l i n e polymer  i s more i n t e n s e  increases w i t h temperature; temperatures Figure  (420K),  o f PPS s p e c t r a i s  t h e n a r r o w component  t h a n i n the amorphous. this  is  i n the  The n a r r o w  5.11 shows t h e h i g h t e m p e r a t u r e  the  quite  crystalcomponent  e s p e c i a l l y marked above T g . A t  t h e n a r r o w component d o m i n a t e s  much  high  spectrum.  spectra of the four  samples.  - 92 -  -i—r 40000  20000  Figure 5.11:  r 20000  PMR spectra of  -40000  • I ' • ' I ' 40000 20000 1  Hz  1  I 0  (a) c r y s t a l l i n e PEEK (b) amorphous PEEK (c) c r y s t a l l i n e PPS (d) amorphous PPS [(a-c) at 430K, (d) at 420K].  - 93 -  Spin-Lattice  5.4.2  Variable for  Relaxation  temperature  spin-lattice  amorphous and c r y s t a l l i n e  (phenylene  sulfide)  Results  relaxation  poly(ether  t i m e s t u d i e s w e r e made  ether ketone)  as d e s c r i b e d p r e v i o u s l y  and p o l y -  i n the experimental  section,  5.3. The T^ v a l u e s of  the f i r s t  of  t h e b u l k sample were o b t a i n e d f r o m t h e  good d a t a p o i n t  9/is f r o m t h e c e n t r e o f  of  the FID;  t h e 90 p u l s e .  typically  A program,  Nicolet  1280 NMR p r o c e s s i n g s o f t w a r e  values.  T13IR i s based on t h e t h r e e parameter  Levy and Peat  (82)  M  for  -  z  T^  M  Q  this  magnitude  was t h e p o i n t  T13IR, p a r t  of  the  ( 8 1 ) , was u s e d t o c a l c u l a t e fit  at  the  T^  e q u a t i o n developed by  calculations:  (l-{l-k[l  - exp(-AT/T )]}exp(-r/T )) 1  (5.10)  1  T  where M  2  is  the magnetization a f t e r  zation at very  long r , k is  (theoretically  k~l),  parameters method i s  in that  it  magnetization. 10%  a measure o f  a n d AT i s  the f i t  Q  accomodates  imperfections  the data a c q u i s i t i o n  are M , k,  Errors  the delay time r , M  for  Q  time.  in relaxation  than perfect  the  magneti-  i n the r . f .  a n d Tj_. The a d v a n t a g e o f a less  is  The  three  this  fitting  inversion of  times are t y p i c a l l y  pulse  the  i n the order  (82). The a m b i e n t  temperature  presented i n Table  5.2.  T^ m e a s u r e m e n t s w e r e c o n s i s t e n t ;  These t i m e s  m e a s u r e m e n t s made o n d i f f e r e n t  are the average o f  occasions  at  and on d i f f e r e n t  they  least  are  two  samples.  The  of  - 94 -  v a r i a t i o n b e t w e e n t h e a v e r a g e d v a l u e s was l e s s times f o r  the p o l y ( e t h e r  poly(phenylene  sulfide).  t h a n t h e amorphous. PPS d i s p l a y i n g  T a b l e 5.2:  ether ketone)  are s h o r t e r  The c r y s t a l l i n e  The o p p o s i t e  the longer  is  t h a n 4%. The than f o r  f o r m o f PEEK h a s a l o n g e r  true of  t h e PPS, w i t h t h e  for  1.35  1.67  amorphous  0.98  1.84  some s c a t t e r  i n the data points  of  the day.  For t h i s  m e n t s made c o n s e c u t i v e l y However, ture  it  are  is noted that  generally  reason,  of a l l  the trends  are r e p r o d u c i b l e .  time against  the p l o t s  the v a r i a b l e  is  the  as f o r  of  Figures  inverse  but  the l i n e w i d t h data, o f one  t h e T^ b e h a v i o u r w i t h 5.12  to  5.15 p r e s e n t  p l o t t e d as t h e l o g a r i t h m o f of the temperature.  con-  measure-  series. temperathe the  The g e n e r a l  t h e same: t h e T^ i n c r e a s e s w i t h t e m p e r a t u r e ,  i n g a maximum v a l u e a t a p p r o x i m a t e l y T g a n d t h e n d e c l i n i n g a t temperatures.  tempera-  sample and t h e s p e c t r o m e t r i c  i n d i c a t e d as b e i n g p a r t  complete r e l a x a t i o n study r e s u l t s , relaxation  of  t h e T^ v a l u e s w e r e n o t a l w a y s r e p r o d u c i b l e  appeared t o depend upon t h e p a r t i c u l a r ditions  amorphous  PPS  crystalline  experiments,  T^  Samples o f PEEK a n d PPS a t  PEEK  ture  the  T^.  T^ V a l u e s ( i n s e c o n d s ) Ambient Temperature.  There i s  relaxation  form  reach-  higher  - 95 1.5  6  •  • 1.0  u LU  cn i-.  •  •  •  • • •  _ _ 0.5  O.Oh  -0.5 2.2  2.4  1  1  2.6  2.8  3.0  i  i  3.2  3.4  3.6  1000/TCK] Figure 5.12:  Log relaxation time versus inverse temperature f o r c r y s t a l l i n e PEEK.  1.5  • l.Or-  A  •  • •  u  LU  •_. 0.5r-  0.0  -0.5 2.2  •  2.4  2.6  2.8  3.0  3.2  3.4  3.6  1000/TCK] Figure 5.13:  Log relaxation time versus inverse temperature f o r amorphous PEEK.  - 96 -  u  LU  to  -0.5  Figure 5.14:  Log relaxation time versus Inverse temperature f o r c r y s t a l l i n e PPS ( i n duplicate).  u  LU  to  Figure 5.15:  Log relaxation time versus inverse temperature f o r amorphous PPS ( i n duplicate).  - 97 -  The a m o r p h o u s m a t e r i a l s tures.  This  i s because o f  show some d i s c o n t i n u i t y  the onset of c r y s t a l l i z a t i o n  sample began t o c r y s t a l l i z e  d u r i n g the course o f  Thus,  only of real  t h e amorphous d a t a i s  transition ture  temperature,  itself.  370K ± 7K  measurements. glass  transition  a transition  The  tempera-  i n the region  an a b r u p t decrease  of  at  (97°C).  maximum Ti^ f o r  of  the c r y s t a l l i n e  crystalline  the c r y s t a l l i n e  t h e PEEK s a m p l e i s  Throughout  PPS, 2 . 8  the temperature  PEEK i s  greater  the c r y s t a l l i n e The l n ( T i )  s a m p l e s i s more c o n t i n u o u s .  about 4.2 s at  s a t 4 1 0 t o 420K  360 t o 370K  range,  The  (137-147°C)  (87-97°C).  the r e l a x a t i o n time o f  than that of  T]_ v a l u e s o f PPS a r e a p p r o x i m a t e l y  t h e amorphous f o r m .  the Conversely,  t h e same f o r b o t h t h e a m o r p h o u s  and  samples. v s 1/T p l o t s  A c t i v a t i o n energy estimates presented i n Table 5.3. greater  above T g .  t h e T^  and i n r e c o g n i z i n g t h e g l a s s  a n d t h e T^ o f PPS e x p e r i e n c e s  The T ^ b e h a v i o u r  and f o r  tempera-  s i g n i f i c a n c e below the  The a m o r p h o u s PEEK i n d i c a t e s  410K ± 7K ( 1 3 7 ° C )  at higher  than that  PEEK m o r p h o l o g i e s  of  are l i n e a r  i n the low temperature  obtained from the slopes  of  region.  the l i n e s  The a c t i v a t i o n e n e r g y o f t h e c r y s t a l l i n e  t h e a m o r p h o u s . The a c t i v a t i o n e n e r g y o f  a r e t h e same, a n d s i g n i f i c a n t l y  larger  are PPS  the  is  two  t h a n t h e PPS  energies. The T^ v a l u e s d i s c u s s e d a b o v e r e f e r whole sample. spin-lattice  I n some c a s e s h o w e v e r , relaxations.  t o t h e a v e r a g e T^ o v e r  t h e samples e x h i b i t e d two  T h e s e w e r e more c l e a r l y  transformed spectra than i n the FIDs. A graphic Figure  5.16.  This  shows t h e p a r t i a l l y  seen i n the  illustration  r e l a x e d spectrum o f  the distinct  frequency is  given  crystalline  in  - 98 -  Table 5 . 3 :  A c t i v a t i o n , Energies Expressed I n k J m o l ' , Obtained from t h e Low T e m p e r a t u r e P o r t i o n o f t h e I n vs Plots. Regression Error I n Brackets. 1  PEEK  PPS  crystalline  1 3 . 3 (±6%)  8 . 6 (±4%)  amorphous  1 3 . 3 (±2%)  4 . 9 (±7%)  poly(phenylene  sulfide)  after  a 180-r-90  sequence, w i t h r b e i n g 0.6 s ;  t h e s p e c t r u m was c o l l e c t e d a t a m b i e n t t e m p e r a t u r e . n a r r o w components a r e p r e s e n t . magnetizations that  relaxation  •0000  Figure  5.16:  feature  o f t h e two components a r e o f o p p o s i t e  t h e b r o a d component,  has t h e l o n g e r  The r e m a r k a b l e  Both t h e b r o a d and  sign,  the  indicating  which has a n e g a t i v e m a g n e t i z a t i o n a t time.  40000  A partially  is that  20000  0  -20000 -40000 -40000  Hz  r e l a x e d s p e c t r u m o f c r y s t a l l i n e PPS.  r-0.6s,  - 99 -  Two d i s t i n c t talline  relaxations  f o r m s o f PEEK a t a l l  a r e f o u n d i n t h e amorphous and t h e temperatures.  I n PPS, o n l y t h e  s a m p l e shows t w o c o m p o n e n t s o f d i f f e r i n g T]_. at  temperatures below Tg.  intense  Moreover  is  difficult  2,  versus  r plot.  t o measure t h e  If,  however,  they are unresolvable  close  i n value but also  greater  than that  the FID.  of  individual  (83).  In this  relaxations.  spectra.  the p r o p o r t i o n o f  estimates  collected  of  i n the p r o j e c t .  of  it  sweep w i d t h was a d i s a d v a n t a g e b e c a u s e ,  smaller  values  for  the work.  intensities.  intensity  of the e a r l y points  c o m b i n e d made p o s s i b l e  the  those smaller  I n most  Still,  the  in eye.  first than  respects,  in increasing and  the  the  transformed the  of the broad p o r t i o n i n t h e F I D . The  a reasonable estimate of  The r e s u l t s  so much  dominates  t h e n a r r o w c o m p o n e n t due t o  sweep w i d t h a n d t h e r e l a t i v e  component  of  p o r t i o n o f t h e F I D was l o s t  resolution of  reduced because o f the l o s s factors  the bulk of  s h o r t T ^ was more p o o r l y r e s o l v e d .  s p e c t r a show h i g h e r  too  c o n f i d e n t l y by  The sweep w i d t h was 1 2 5 , 0 0 0 H z ,  the narrower  component o f  is  of  t h e component h e i g h t s  t h e s e measurements were p a r t  the e a r l i e s t  by a f a c t o r  t h e two T^s were o b t a i n e d f o r  5 0 0 , 0 0 0 Hz u s e d f o r  8 (is,  magnetization  completely  the width of  dwell time to  the  t h e b r o a d component  The c u r v e s c o u l d b e s e t q u i t e  The s p e c t r a u s e d f o r  only  Normally,  c a s e , n o t o n l y a r e t h e T^s  t w o PEEK s a m p l e t y p e s b y d i r e c t m e a s u r e m e n t o f the frequency  true  rate.  t h e t w o T^ v a l u e s d i f f e r  t h e n a r r o w component t h a t  I n t h i s work,  is  A t T g , t h e n a r r o w c o m p o n e n t becomes more  t w o s e p a r a t e T ^ s may be e x t r a c t e d f r o m a n a n a l y s i s M(r)  crystalline  this  a n d t h e t w o c o m p o n e n t s show t h e same r e l a x a t i o n  It  crys-  the  two  individual  are presented i n Table 5.4.  t h e b r o a d component a g r e e w e l l w i t h t h e T^ v a l u e s  is  The obtained  - 100 -  for  t h e b u l k sample f r o m an e a r l y p o i n t  n a r r o w c o m p o n e n t r e l a x e d more q u i c k l y Spin-lattice netic  oxygen,  sub-ambient  relaxation  temperatures  (84). to  than the  sensitive  and i n polymer s t u d i e s ,  the e f f e c t w i t h respect  Table 5.4:  is  of the FID.  this  I n order  t h i s work,  to is  In all  cases  the  broad.  the presence o f of particular  paramagconcern  t o a s c e r t a i n the magnitude  at of  t h e r e l a x a t i o n t i m e s o f an open  S p i n - L a t t i c e R e l a x a t i o n T i m e s f o r t h e I n d i v i d u a l Components o f PEEK, Room T e m p e r a t u r e , T]_ E x p r e s s e d i n S e c o n d s .  broad  narrow  amorphous  0.94 ± 0.03  0.66 ±  0.01  crystalline  1.43  1.32  0.1  ± 0.01  ±  s a m p l e a n d o f a n e v a c u a t e d s a m p l e w e r e d e t e r m i n e d u n d e r t h e same c o n d i tions.  The T ^ o f  t h e e v a c u a t e d s a m p l e was 1 . 8 5  h a d a T^ o f  1.64  s,  between the  two,  given the  did not warrant  (11% l o w e r ) .  literature.  inherent  was d e c i d e d t h a t inaccuracy of  the  t h e T^  discrepancy measurements,  r e p e a t i n g the work w i t h evacuated samples.  and g e n e r a l b e h a v i o u r noted that  It  s and t h e open sample  of  the r e l a x a t i o n remains u n a f f e c t e d .  t h e use o f b o t h e v a c u a t e d and open samples  is  The  trends  It  may b e  found i n  the  - 101 -  5.5  DISCUSSION  5.5.1  Line-Shape  The d u a l i t y the presence o f the s i g n a l  Is  Discussion  of  the p r o t o n spectra o f  two t y p e s o f m o l e c u l a r m o t i o n s .  t w o somewhat d i f f e r e n t  5.5.la  and p o l y ( p h e n y l e n e  cases w i t h r e s p e c t  of and  narrowing.  are presented  as  line-shape.  PEEK  Below T g , intense  t h e n a r r o w c o m p o n e n t o f PEEK t e n d s t o b e s l i g h t l y  i n the spectra of  t h e amorphous f o r m t h a n o f  The r e a s o n u n d e r s t o o d f o r  this  amorphous m a t e r i a l  greater mobility  possible  allows  i n the c r y s t a l l i n e  The e f f e c t  is  that  the c r y s t a l l i n e .  of additional mobility  6  Hz r a n g e  Linewidth  crystalline.  the reduced d e n s i t y o f  the  o f c h a i n segments t h a n  is  i n t h e amorphous sample i s  also  l e s s w i d e i n t h e amorphous t h a n  i s most s e n s i t i v e  to motions  i n the 5x10^  in to  (84).  As t h e t e m p e r a t u r e narrow gradually  the  more  form.  seen i n t h e b r o a d component w h i c h i s  3.3xl0  sulfide)  to  from  i n the l a t t i c e  from those which experience m o t i o n a l  ether ketone)  arises  The b r o a d c o m p o n e n t  due t o t h e p r o t o n s w h i c h a r e h e l d r i g i d  the narrow component, Poly(ether  t h e s e two p o l y m e r s  increases,  the Gaussian-type  due t o t h e p r o g r e s s i v e  abrupt narrowing of  t h e amorphous l i n e  increase at  line  continues  i n thermal motions.  the glass  transition  is  to The  - 102 explained by the onset o f c o - o p e r a t i v e motions o f l a r g e macromolecular  chains. Unfortunately,  t e m p e r a t u r e were such t h a t 20K  above Tgj  the e f f e c t  the experimental  t h e maximum t e m p e r a t u r e  of  temperatures  further  segments o f limits  on  the  the  o b t a i n a b l e was  only  above t h e Tg were  not  observed.  5 .5. l b  PPS  Below T g ,  it  is  the c r y s t a l l i n e  p r o m i n e n t n a r r o w component.  This  PEEK s p e c t r a a n d a l s o c o n t r a r y different forms  is  is  f o r m o f PPS w h i c h d i s p l a y s contrary  t o what i s  to expectation.  It  is  uncured r e s i n and,  for  this  although i t  l o w e r m o l e c u l a r w e i g h t and i s of oligomer.  suggested t h a t  discrepancy:  displays higher also  likely  The d i f f e r e n c e PPS i s  o f PPS c r y s t a l l i n i t y  the its  and amorphous  t h a n t h e d i f f e r e n c e between t h e two forms  is higher  between the c r y s t a l l i n e  than that  o f PEEK;  and amorphous l i n e w i d t h  since  the  the greater  is not  i n the glass  transition region.  of  degree  difference  unexpected.  PEEK, i n s p e c t r a o f t h e a m o r p h o u s PPS, t h e b r o a d  significantly  of  protons.  PEEK. T h i s may b e e x p l a i n e d i n t e r m s o f c r y s t a l l i n i t y  J u s t as f o r  despite  i n l i n e w i d t h between the c r y s t a l l i n e  greater  is  an  proportion  Because c h a i n ends a r e t h e most m o b i l e p o r t i o n o f  has t h e g r e a t e r p r o p o r t i o n o f m o b i l e  spectra of  it  to contain a small  crystallinity,  the  powder i s  crystallinity,  the polymer o f lower molecular w e i g h t ,  the  crystalline  the c r y s t a l l i n e  macromolecule,  narrows  observed f o r  m o l e c u l a r w e i g h t s b e t w e e n t h e amorphous and t h e responsible  a more  The  line  equivalently  - 103 -  abrupt of  increase  i n l i n e w i d t h a b o v e t h e Tg i s  t h e amorphous m a t e r i a l .  samples a t a t e m p e r a t u r e time.  DSC s c a n s o f  sity  of  there  is  lineshape  5.5.Ic  increases  at  t h e expense o f  above  The  of  inten-  t h e b r o a d one  i m m o b i l e b e l o w Tg  approach  T . E  a r e o f t e n made i n s t e a d o f  Since the Gaussian l i n e w i d t h  t h e s e c o n d moment,  I n t h i s work,  values of  the e a r l y points  t o an even p o l y n o m i a l  i n the receiver  (32).  (which t y p i c a l l y  converged a f t e r  s h o u l d be p o s s i b l e  to calculate  the squared term o f  encountered w i t h t h i s alone.  the  points  about 5 terms).  to zero a t  the  origin.  t h e s e c o n d moment d i r e c t l y  the even p o l y n o m i a l .  a p p r o a c h was t h a t  the  d e a d t i m e be  t h i s was a c h i e v e d b y f i t t i n g  The i m a g i n a r y p o i n t s w e r e e x t r a p o l a t e d l i n e a r l y  as a r e a l p a r t  results  square  Both approaches r e q u i r e d t h a t  o f t h e FID l o s t  For the r e a l p o i n t s  the constant o f  to the  t w o a t t e m p t s w e r e made t o o b t a i n t h e s e c o n d moments  t h e PEEK a n d PPS s p e c t r a .  recovered.  linewidth  is proportional  t h e two methods y i e l d s i m i l a r  values of  It  that  S e c o n d Moments  measurements. of  with  crystallinity.  a n o n s e t o f much i n c r e a s e d m o t i o n .  S e c o n d moment c a l c u l a t i o n s  root  in linewidth  o f PPS i s m a r k e d l y u n l i k e  because t h e c h a i n segments w h i c h were n e a r l y motions  amorphous  these annealed samples c o n f i r m p a r t i a l  the narrow l i n e  liquid-like  crystallization  S e r i e s o f s p e c t r a measured f o r  a b o v e Tg show a n i n c r e a s e  The h i g h t e m p e r a t u r e PEEK. A b o v e T g ,  due t o t h e  The  t h e FIDs c o u l d n o t be  from  difficulty expressed  The d a t a c o u l d n o t b e p h a s e d so as t o s e t  the  - 104 signal  i n the  was due t o  imaginary channel to zero.  the s l i g h t  assymmetry o f  (The r e a s o n f o r  the l i n e  this  failure  shapes.)  The s e c o n d a p p p r o a c h was t o u s e a n i n t e g r a t i o n p r o g r a m t o t h e s e c o n d moment f r o m t h e F o u r i e r lines  of  t h e s p e c t r a d i s p l a y e d some t i l t  exceedingly signal  at  sensitive  frequencies  uneven b a s e l i n e s  The a t t r a c t i v e that  rigid  the s i g n a l  farthest  a n d t h e s e c o n d moment  contribution  scatter  is  from the wings  away f r o m t h e c e n t r e  frequency  the extent  feature  The c r y s t a l l i n e  structure  (79).  t h e amorphous f o r m o f  The m o l e c u l a r  the  must be  t h e same p o l y m e r  systems i n d i c a t e s  (75). Certainly,  explanation for  the  t h e PEEK s a m p l e . the  than  this pattern  increased  t o t h e more r i g i d c r y s t a l l i n e  c o n s t r a i n e d by the  that  a longer r e l a x a t i o n time  r e l a x e s more q u i c k l y b e c a u s e o f relative  of  place.  r e l a x a t i o n was e s t a b l i s h e d f o r  of the polymer chains  for  Discussion  morphology g e n e r a l l y e x h i b i t s  molecular motion is  and  b e t w e e n t h e t w o v a l u e s c a n p r o v i d e as e s t i m a t e  P r e v i o u s work on o t h e r macromolecular  amorphous m a t e r i a l  The  experimentally  of the r i g i d l a t t i c e  of motional narrowing which takes  crystalline  the  i n t h e moment c a l c u l a t i o n s  a b o u t s e c o n d moments o b t a i n e d  Spin-Lattice Relaxation  crystalline  base-  abandoned.  k n o w n . The d i f f e r e n c e  longer  the  t h e y may b e c o m p a r e d t o v a l u e s c a l c u l a t e d t h e o r e t i c a l l y  lattice.  5.5.2  to  caused excessive  t h i s m e t h o d was a l s o  is  transform. Unfortunately,  calculate  The  motion  structure;  crystallites.  t h e T^ b e h a v i o u r o f PPS i s  of  less  - 105  clear.  This  uncured, of  author  t h a t because  the average molecular weight  t h e amorphous,  tion of  suggests  R-4 p o l y m e r .  i n the c r y s t a l l i n e  Relaxation rates  approximately  t h e same b e c a u s e o f  chain lengths  present  the c r y s t a l l i n e The l n ( T ! )  vs  plot  for  that  t h e T^ v a l u e  plots  discrepancy  is  of  5xl0"^s;  systems,  for  low  of  the  5.12  i n Figure at  to  5.15  5.5.  T^  MJJ a n d  relaxation.  differ  The l a t t e r  the glass  relaxa-  identical  a longer  are  shorter  from plot  transition  the suggests  tempera-  Very s i m i l i a r example,  10"^ to  the r e l a t i v e  Activation  temperature  at which  This  WT =«1. c  For  The maximum o f  the  ln(T^)  vs  l i n e - s h a p e s have been o b s e r v e d i n  The d o m i n a n t m o t i o n s lO'-'s,  paucity  energies  the  t i m e a t w h i c h T^ i s m i n i m a l w o u l d be  i n t h e l o w t e m p e r a t u r e T^ p r o f i l e  of  of  the  t o a maximum T^ b e t w e e n t w o t r a n s i t i o n s  5.17.  indicate  Figures  temperatures.  shown i n F i g u r e the order  even a t  the  such a f a s t m o t i o n w o u l d o n l y be p r o m i n a n t  corresponds  5.4).  for  t h e T^ a p p e a r s as a maximum a t T g .  the c o r r e l a t i o n  considerably higher  Figure  propor-  e x p l a i n e d b y t h e v e r y h i g h f i e l d a t w h i c h t h i s w o r k was  200 MHz f i e l d ,  seen h e r e ,  to exhibit  s h o u l d be s h o r t e s t  The T ^ m i n i m u m i n d i c a t e s  approximately  and amorphous PPS o f  polymer'  i n t h i s work,  PPS s p e c t r u m ,  weight  a  which promote s p i n - l a t t i c e  w o u l d be l i k e l y  a 'theoretical  However,  done.  than the molecular  the e x t r a m o b i l i t y  i n the l a t t e r  1/T  is  o f P P S , amorphous and c r y s t a l l i n e ,  I n samples o f c r y s t a l l i n e  ture.  less  powder  The v i r g i n r e s i n a l s o c o n t a i n s  temperatures.  M,,,  is  the c r y s t a l l i n e  low molecular weight molecules which are r e s p o n s i b l e  narrow spike present  tion.  -  the high frequency  o b t a i n e d f r o m T^ p l o t s  are  this  plot  (shown  in  other  o f benzene  a t Tg h a v e c o r r e l a t i o n  a n d t h e T^ maxima a t of  1/T  at  (85) times  temperature  motions. typically  less  than  - 106 -  Figure  5.17:  The T^ t e m p e r a t u r e p r o f i l e  the a c t i v a t i o n NMR e s t i m a t e s  energies  may r e f l e c t  (30).  in that  a f i x e d energy b a r r i e r  sample i t s e l f  Also,  it  contains of  c a l c u l a t e d by s i m i l a r  for  rotation,  crystalline,  regardless  must be remembered t h a t  is  of  logical  samples c l e a r l y  d e n s e , more d i s o r d e r e d ,  However, suggests  amorphous  The a c t i v a t i o n e n e r g y o f ably with  that  the d i f f e r e n c e  material. somewhat  suspect  approaching  between t h e two morpho-  f r e e r molecular motion i n the  less  phase.  the c r y s t a l l i n e  found by other workers.  study of c r y s t a l l i n e  the  t h e PEEK c r y s t a l -  a h i g h d e g r e e o f amorphous  t h e PPS a c t i v a t i o n e n e r g i e s  other  techniques.  t h e s l o p e o f t h e a c t i v a t i o n l i n e was t a k e n f r o m p o i n t s  t h e maximum T ^ v a l u e .  their  Nevertheless,  t h e y may b e c o m p a r e d w i t h e a c h  a c t i v a t i o n e n e r g i e s o f PEEK, a m o r p h o u s a n d  The r e l i a b l i t y since  d e t e r m i n e d by o t h e r methods  o f other polymers  polymer morphology. line  (85).  are u s e f u l  and w i t h e n e r g i e s The l i k e  o f benzene  PPS c o m p a r e s n o t  S c h l i c k and McGarvey  unfavour-  (32)  PPS, a l s o b y PMR, f o u n d a c t i v a t i o n  in  energies  - 107 -  by two methods. 11.8 kJ m o l " of  The T^ t e c h n i q u e y i e l d e d a s i n g l e  and t h e l i n e - w i d t h a n a l y s i s  1  6.2 and 13.7 k J m o l " .  a c t i v a t i o n energy  gave two r e l a x a t i o n  T h i s m o t i o n was a s s i g n e d t o t h e  1  of  processes  phenylene  r o t a t i o n a b o u t t h e S-S b o n d . Other estimates  of a c t i v a t i o n energies  t i o n s h a v e b e e n made, b u t n o t larger. mol"  1  Garroway e t  for  as 40 t o  (86,87)  (88),  and H a g e l l and Beck ( 8 9 )  80 k J  The o r i g i n s  spin-lattice  the f o u r polymer  of  t o b e due t o  i n p o l y s t y r e n e made b y  relaxation times,  samples s t u d i e d , the c r y s t a l l i n e ether  i s o l a t e d molecules o f For a l l  d i f f u s i o n was p r e d o m i n a n t ,  as  large  of  interesting  poly(phenylene  less  i m p o r t as i t  low molecular weight  t h e PPS s a m p l e s a b o v e T g ,  b o t h t h e n a r r o w and t h e b r o a d  t h e same r e l a x a t i o n .  allow for  an  observed  ketone).  This behaviour  indicates  m o r p h o l o g i c a l phases are i n such c l o s e p r o x i m i t y  systems.  is  t h e n a r r o w PPS c o m p o n e n t a r e o f  have i n c r e a s e d m o b i l i t y .  interactions  Theoreti-  gave a c t i v a t i o n e n e r g i e s  and f o r b o t h forms o f p o l y ( e t h e r  experience  60 k J  1  p h e n o m e n o n . Two T ^ s a r e f o u n d f o r  thought  considerably  mol" .  three out of  sulfide)  are  r e p o r t e d an a c t i v a t i o n energy o f  o f phenyl group r o t a t i o n s  The p r e s e n c e o f d i s t i n c t for  PPS o r PEEK. A l l  rota-  t h e p h e n y l r i n g m o t i o n i n t h e DGEBA e p o x y p o l y m e r s .  cal calculations Tonelli  al.  for  f o r phenylene group  that  which  spin  components that  strong  the  for  T^ s p i n d i f f u s i o n  is  two  dipole  s p i n e n e r g y t o be t r a n s p o r t e d b e t w e e n t h e  The maximum d i s t a n c e  is  several  spin  tens  of  nanometers. On t h e o t h e r h a n d , plays  t w o T^ v a l u e s ,  PEEK a t a l l  thus  temperatures  and i n b o t h forms  s u g g e s t i n g t h e absence o f  spin diffusion  disand,  - 108  therefore, partial  large  ( > 1 0 nm) s e p a r a t e d o m a i n s o f  s p i n d i f f u s i o n may b e p r e s e n t b u t  difficult  to determine.  The m a j o r i t y  spin d i f f u s i o n present  (32,68,77)  is primarily  or mixtures  noticed.  i n blends  However,  crystalline  5.6  (>60%)  Tanaka (75)  t h e two p h a s e s .  the e f f e c t  of  Of  in semi-crystalline (74,90)  isotactic  that  course,  t h i s w o u l d be  of spin relaxation studies  does r e p o r t  samples o f  found  polymers,  s e p a r a t e T^s  on s e p a r a t e T^s o f  and  it  are highly  polypropylene.  SUMMARY AND CONCLUSION OF PMR WORK  Proton broad-line b e e n made f o r fide)  -  and s p i n - l a t t i c e  amorphous and c r y s t a l l i n e  and p o l y ( e t h e r  ether ketone),  at  r e l a x a t i o n measurements  have  samples o f p o l y ( p h e n y l e n e temperatures  sul-  from ambient  to  430K. The l i n e - s h a p e s tons  (broad l i n e )  of a l l  samples i n d i c a t e  and m o b i l e p r o t o n s  o f PPS a t h i g h t e m p e r a t u r e s ,  (narrow l i n e ) .  the broad l i n e  decreases w i t h i n c r e a s i n g temperature and, transition, lattice  the l i n e w i d t h decreases  r e l a x a t i o n times are longer  the r e l a x a t i o n data, Partially  estimates  the presence o f r i g i d  is  Except f o r  dominant.  The  i n the region of  abruptly.  Also,  linewidth the  glass the  temperature.  o f a c t i v a t i o n e n e r g i e s were  relaxed spectra indicate  spectra  at the Tg,  t h a n a t any o t h e r  pro-  spinFrom  obtained.  separate r e l a x a t i o n times  for  the  b r o a d and n a r r o w components b e l o w t h e T g . S e c o n d moment v a l u e s w e r e n o t c a l c u l a t e d b u t c o u l d b e a t a date.  This would require  t h e use o f a p u l s e program w h i c h w o u l d  s p e c t r a w i t h even b a s e l i n e s .  The r e c e i v e r  c h a n n e l s h o u l d be  later yield  triggered  - 109 -  before  the f i n a l  pulse  i n order  t o e s t a b l i s h a good b a s e l i n e b e f o r e  F I D a n d p h a s e a l t e r n a t i o n s h o u l d b e e m p l o y e d . The e a r l y p o i n t s s h o u l d be e x t r a p o l a t e d by t h e method d e s c r i b e d i n 5 . 5 . 1 f i n a l value of  moments c o u l d t h e n b e c o m p a r e d w i t h v a l u e s  and  calculated for  the  the  obtained from the  the  second  crystal  calculations.  T h i s p r o t o n NMR s t u d y , light  lost  t h e s e c o n d moment c a l c u l a t e d b y i n t e g r a t i o n o f  s p e c t r a i n t h e f r e q u e n c y d o m a i n . The v a l u e s  structure  (c)  the  o f two s e m i - c r y s t a l l i n e  polymers,  some c o n t r a s t s b e t w e e n a m o r p h o u s a n d c r y s t a l l i n e  b e t w e e n PEEK a n d PPS. The NMR l i n e s h a p e s on temperature  show t h e n a i v e t y  and t h e dependence o f  amorphous phase and t h e b r o a d t o t h e c r y s t a l l i n e .  temperature.  is  as p r o m i n e n t  lineshape  to  the protons  vary  with  s e e n as t h e i n c r e a s e  i n the c r y s t a l l i n e  as i n t h e  to  and  The a m o r p h o u s  and t h e p r o p o r t i o n s  Above T g , t h e o n s e t o f m o b i l i t y ,  the narrow l i n e ,  polymers  of assigning the narrow l i n e  a r e n e a r l y as b r o a d as t h e c r y s t a l l i n e  brings  of  amorphous  sample. Compared t o PPS, t h e l i n e s h a p e o f PEEK shows r e l a t i v e l y m o t i o n above t h e g l a s s is  closely related to  s t r e n g t h and s t i f f n e s s  transition.  It  is  likely  the remarkable a b i l i t y properties  that  the lack of  o f PEEK t o  PPS; t h i s  The p r e s e n c e o f leads  to  two d i s t i n c t  the inference  nanometers) contributing  of  of  the superior  r e l a x a t i o n times  large  motion  a b o v e T g . The a c t i v a t i o n e n e r g i e s  is noted i n l i g h t  rigid  regions  for  several  (37).  PEEK.  polymer  tens  i n t h e p o l y m e r w h i c h may h a v e a r e i n f o r c i n g e f f e c t , to the strength of the m a t e r i a l  from  PEEK  strength of  i n the single (of  free  maintain  r e l a x a t i o n data suggest higher motional a c t i v a t i o n energies than f o r  little  of again  - 110 6.  6.1  CONCLUSION  GENERAL REMARKS  I n coming y e a r s , to take a greater  the h i g h performance  share o f the composite m a t r i x market.  the f a b r i c a t i o n techniques plastic  will  i t e market  to  and an i n c r e a s i n g a v a i l a b i l i t y  industry.  Other t h e r m o p l a s t i c s ,  of  the  f i e l d has a b r i g h t  encouraged by the commercial developments. especially  microscopic  it  future  thermo-  resins  newer t o t h e  of polymers.  for  can p r o v i d e  as w o r k e r s  There i s  i n the area of c o r r e l a t i n g  properties  promising techniques molecules:  in  compos-  t h a n PPS a n d PEEK a r e a l s o c o m p e t i n g w e l l .  The r e s e a r c h i n t h i s  learned,  continue  Improvements  p o l y m e r s make t h e s w i t c h f r o m t h e t h e r m o s e t t i n g e p o x y  more a t t r a c t i v e  still  the microscopic  one o f  nature of  i n f o r m a t i o n about b o t h the molecular the  are  much t o b e  the macroscopic  S o l i d s t a t e NMR i s  the study o f  and t h e m o l e c u l a r m o t i o n o f  6.2  thermoplastics  and the  most  macrostructure  polymer.  SUMMARY  The p u r p o s e o f two t h e r m o p l a s t i c  this  particular  polymers,  s t u d y was t o u s e NMR t o  poly(ether  ether ketone)  and  investigate  poly(phenylene  sulfide). A l t h o u g h b o t h PEEK a n d PPS h a v e v e r y g o o d c h a r a c t e r i s t i c s  for  use  - Ill as f i b r e  composite m a t r i c e s ,  erties.  This  b y DSC.  The g l a s s  is  o f PEEK a r e a l l  first  i n most cases,  apparent  transition,  at least  r e s o l u t i o n CP/MAS s p e c t r a . assigned to the f i v e i n g and r e f e r e n c e  and m e l t i n g  than those o f  n a t e d and n o n - p r o t o n a t e d )  two i n e q u i v a l e n t  high  c a r b o n s o f PEEK w e r e  The PPS  dephas-  spectral  carbon types  (proto-  dipolar  experiment.  crystalline  counterparts,  phous and c r y s t a l l i n e the greater  the d i f f e r e n c e  degree o f c r y s t a l l i n i t y  talline  lines.  Variable-contact-time n o t made o n PPS.  that  reflect  their  i n l i n e w i d t h s between the  amor-  Those f o r  the shorter  for  PEEK i n d i c a t e  as f u n c t i o n s  of  crys-  t h e optimum c o n t a c t  were times  than f o r non-protonated carbons. times f o r  the  Arrhenius plots  It  amorphous  the spin-locked proton  magnetization  material.  spectroscopy allowed the polymers  temperature.  spectra  t h e CP/MAS e x p e r i m e n t s  a n d g r e a t e r m o l e c u l a r m o t i o n i n t h e amorphous The PMR w i d e - l i n e  reflects  The h i g h r e s o l u t i o n  that  optimum c o n t a c t  t h e s h o r t e r T^p o f  This  suggest a s u p e r p o s i t i o n o f  measurements  f o r p r o t o n a t e d carbons are s h o r t e r thought  than  o f PPS.  crystallinities  and amorphous  are broader  i s more m a r k e d i n t h e PPS s p e c t r u m .  o f samples o f v a r i o u s  material  temperatures  i n the  were e a s i l y d i s t i n g u i s h e d by t h e  A l t h o u g h t h e CP/MAS s p e c t r a o f b o t h p o l y m e r s  is  measured  The a i d o f d i p o l a r  t o m o d e l compounds was r e q u i r e d .  prop-  PPS.  o f PEEK became a p p a r e n t  of the spectrum.  a s s i g n m e n t was s t r a i g h t f o r w a r d :  dephasing  crystallization  The s e v e n i n e q u i v a l e n t  lines  superior  i n the t r a n s i t i o n temperatures  50°C h i g h e r  The more c o m p l e x s t r u c t u r e  PEEK d i s p l a y s  t o be  of relaxation  studied  measure-  ments y i e l d e d a c t i v a t i o n energy e s t i m a t e s w h i c h were i n k e e p i n g w i t h  the  - 112 properties  of  the polymers.  larger  (PEEK h a s h i g h e r  sition  temperature).  than f o r  crystalline  the morphologies It glass  of  s t r e n g t h and s t i f f n e s s  PEEK m o t i o n was  and a h i g h e r  PPS, s u g g e s t i n g a g a i n a l a r g e the  two  In all  the glass  difference  the behaviour o f  cases t h e s p i n - l a t t i c e  transition  P e r h a p s t h e phenomenon i s p a r a l l e l seen i n mechanical  temperature.  between  It  tures.  behaviour  than the c r y s t a l l i n e  J u s t as i n t h e CP/MAS s p e c t r a ,  ence i n l i n e w i d t h  is  larger  for  at  that  PEEK t h a n f o r  m o l e c u l a r m o t i o n i n t h e PPS l a t t i c e c o r r e l a t e s w i t h the observation t h a t its  transition  strength properties point.  times  temperature.  tan 6 at  at  t h e T g as  the  responsible  spectra at a l l  for  PPS.  there  amorphous  tempera-  considerably  t h a n i n t h e PEEK l a t t i c e . PEEK r e t a i n s  differ-  The l i n e s h a p e  is  a remarkable  even a t temperatures  the  the  the amorphous/crystalline  s p e c t r a measured above t h e Tg s u g g e s t t h a t  tion of  the  spectroscopy.  Similar motional narrowing is  being narrower  in  i s u n c e r t a i n why  o n s e t o f c o o p e r a t i v e m a i n c h a i n m o t i o n causes t h e n a r r o w i n g o f  spectra,  lower  relaxation  to the maximization o f  The l i n e w i d t h a l s o shows d i s t i n c t i v e  spectral width.  tran-  the materials  t h e r e l a x a t i o n mechanism s h o u l d be most u n e f f e c t i v e  Tg w h i c h i s  glass  forms.  t o observe  transition region. at  for  The a c t i v a t i o n e n e r g y o f a m o r p h o u s PPS was  was i n t e r e s t i n g  were l o n g e s t  The e n e r g y b a r r i e r  above t h e  of more  This proporglass  - 113 -  6.3  SUGGESTIONS FOR THE CONTINUATION OF THE STUDY  This  study of  are a v a r i e t y (i)  t h e r m o p l a s t i c s b y NMR i s b y no means c o m p l e t e .  of other  Spin-lattice  e x p e r i m e n t s w h i c h r e m a i n t o be done.  r e l a x a t i o n times  worth measuring. work,  The r e s u l t s  (ii)  i n the  (iii)  A knowledge o f  interpretation of  the  t h e T-^ r e l a x a t i o n i s 1 3  C contact  i n g which takes  place.  Low t e m p e r a t u r e  studies  data requires tures  rigid-  the motional  A c t i v a t i o n energy c a l c u l a t i o n s  the l i m i t i n g value of  impor-  times.  o f r e l a x a t i o n a n d s e c o n d moments  is  t o do v a r i a b l e  narrow-  could  f r o m s e c o n d moment  the l i n e w i d t h  at  low  t e m p e r a t u r e CP/MAS, i n t h i s  expected i n the near f u t u r e .  a t a b o v e Tg t e m p e r a t u r e s  could prove  Lineshape d e c o n v o l u t i o n and s p e c t r a l It  into  the  tempera-  (32) .  The c a p a c i t y tory,  insight  well  linewidth  also  p  the  s e c o n d moments may g i v e  a l s o be u s e f u l .  (v)  c o u l d be c o m p a r e d t o  S e c o n d moment m e a s u r e m e n t s c o m p a r e d t o t h e c a l c u l a t e d lattice  (iv)  i n t h e r o t a t i n g f r a m e w o u l d be  as t h e t w o m e t h o d s r e s p o n d t o m o t i o n s o f a p p r o x i m a t e l y  same f r e q u e n c y . tant  There  may b e p o s s i b l e  various  to estimate  components.  labora-  The h i g h r e s o l u t i o n  spectra  interesting. s u b t r a c t i o n c o u l d be done.  the r e l a t i v e p r o p o r t i o n s  of  the  A m a j o r a c h i e v e m e n t w o u l d be a c o r r e l a t i o n  NMR d a t a t o t h e f r a c t i o n a l  crystallinity  values  found by  of  X-ray  spectroscopy. Looking f a r t h e r ber  afield,  o f h i g h performance  PEEK a n d PPS a r e o n l y t w o o f a g r o w i n g num-  thermoplastics.  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B  DA -  variable  DO -  4.0  CP/MAS p r o g r a m DA i s  DB -  2.6 x  r e p l a c e d b y D2 a n d i s  10'  1 ms  5  in  - 122 -  PULSE PROGRAM FOR DIPOLAR DEPHASING EXPERIMENT  A  D  0  1  1  C  B +V  2  +W  2  B  +X  3  3  1  4  1  B  5  0  F  6  0  7  1  8  1  9  B  A  2  B  0  E  +Y  1  +W  -W  6  1  -V +X  +Y +Y  +W +W  -W  F  DI -  6.0 x  10"  6  DA -  5.0 X 1 0 "  D3 -  2.5 x  10'  2  DO =  4.0  3  DB -  4.0 x  10  -  - 123 -  APPENDIX  II  VARIABLE CONTACT TIME PLOTS FOR PEEK  - 124 -  o.s  -1.5l -3.0  i  I  -2.0 LN  OF  CONTACT  i  I  -1.0  0.0 TIME  CLN  1.0  2.0  MSEC]  VRRIABLE CONTACT TIME FOR CRYSTALLINE  PEEK  0.5  -l.sl  -3.0  i  i  -2.0  LN  VARIABLE  i  -1.0 OF  CONTRCT  i  0.0 TIME  [LN  1.0 MSEC]  CONTACT TIME FOR CRYSTALLINE  PEEK  I  2.0  - 125 -  o.s  -2, o  - i. u LN  VARIABLE  OF  CONTACT  ***** TIME  CLN  MSEC]  CONTACT TIME FOR AMORPHOUS FEEK  

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