UBC Theses and Dissertations

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UBC Theses and Dissertations

Emulsion polymerization of isoprene Johnson, Arthur Lee 1950

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EMULSION POLYMERIZATION OF ISOPRENE BY A r t h u r Lee Johnson, Be/A. A T h e s i s submitted In P a r t i a l F u l f i l m e n t o f The Requirements f o r the Degree of MASTER OF ARTS i n the Department of CHEMISTRY The U n i v e r s i t y of B r i t i s h Columbia A p r i l I9$0 ABSTRACT The e m u l s i o n p o l y m e r i z a t i o n o f i s o p r e n e h a s b e e n p r o d u c e d b y u s i n g a s i n i t i a t i n g a g e n t s v a r i o u s compounds w h i c h a r e known t o d i s s o c i a t e t o a c e r t a i n e x t e n t i n s o l u -t i o n i n t o f r e e r a d i c a l s . The r a t e o f t h e r m a l d e c o m p o s i t i o n o f some o f t h e d i a z o t h i o e t h e r s e m p l o y e d a s i n i t i a t i n g a g e n t s h a v e b e e n m e a s u r e d b y o b s e r v i n g t h e r a t e o f e v o l u t i o n o f n i t r o g e n f r o m a s o l u t i o n o f t h e compounds i n b u t y l p h t h a l a t e . ACKNOWLEDGEMENT I wish t o acknowledge the guidanoe and I n t e r e s t o f Dr.. R.H. C l a r k , who has su p e r v i s e d the work done on the p o l y m e r i z a t i o n of isoprene a t t h i s u n i v e r s i t y . Acknowledgement i s a l s o made of the h e l p of Dr.. J.8. Tapp, A s s i s t a n t D i r e o t o r of Research, Poylmer C o r p o r a t i o n of Canada, and the f i n a n c i a l support o f the Polymer C o r p o r a t i o n through g r a n t s from the N a t i o n a l Research C o u n c i l which made p o s s i b l e the c o n t i n u a t i o n o f t h i s work d u r i n g the summers of 1948 and 1949, Art h u r Lee Johnson TABLE QF CONTENTS HISTORY 1 THEORY ; . . . , 4 EXFERBffiNTAL PART I (aj p r e p a r a t i o n o f Mono and D i s u l p h i d e s 9 (b) R e s u l t s 12 PART I I (a) p r e p a r a t i o n s 14 (b) Decomposition of Diazo T h i o E t h e r s 17 (c) Graphs 21 (4) R e s u l t s o f p o l y m e r i z a t i o n 24 TECHNIQUES (a) Y i e l d s 25 (b) P r e p a r a t i o n of A n t i - o x i d a n t 25 (c) P r e c i p i t a t i o n o f Latex , 25 (d) Determination of G e l Co$$ent 26 CONCLUSIONS 28 EMULSION POLYMERIZATION OF ISOPRENE HISTORY . As e a r l y as 1835 attempts were made t o deduce the s t r u o t u r e of n a t u r a l rubber by p y r o g e n e t i c decomposition. H o w e v e r , i t was not u n t i l 1862,:that G r e y i l l e W i l l i a m s i s o l a t e d a hydrocarbon having.a b o i l i n g p o i n t o f 27-38° C from the low b o i l i n g , f r a c t i o n o f the d i s t i l l a t e o f n a t u r a l rubber. T h i s hydrocarbon he named i s o p r e n e , ? but i t was twenty y e a r s l a t e r b efore T l l d e n proposed the present s t r u c t u r a l formula f o r Isoprene. W a l l a c h showed t h a t the h i g h e r b o i l i n g f r a c t i o n s of the d i s t i l l a t e from n a t u r a l rubber were e i t h e r dimers, t r i m e r s , o r o t h e r r e l a t e d homo-logues o f Isoprene, I t was a l s o soon observed t h a t i s o p r e n e on prolonged s t a n d i n g a g a i n formed r u b b e r l i k e p r o d u c t s . . I t appeared, t h e r e f o r e , t h a t i s o p r e n e and rubber were g e n e t i c a l l y , r e l a t e d . , I t was, o f course,, a l o n g step from the f i r s t o b s e r v a t i o n s t o the a c t u a l p r e p a r a t i o n o f syn-t h e t i c rubber from isoprene., From 1885 on r e s e a r c h i n the f i e l d of rubber I n c r e a s e d , and i n 1906, H a r r i e s , as a r e s u l t of e x t e n s i v e r e s e a r o h g r e a t l y extended the knowledge of the chemistry of rubber by means of ozone d e g r a d a t i o n o f n a t u r a l rubber. He found t h a t decomposition o f the ozonides w i t h hot water gave an almost q u a n t i t a t i v e y i e l d o f d e r i v a t i v e s o f t h e u n i t group GijHg, a . t h a t i s , l e v u l i n i o aldehyde, l e v u l i n i o a c i d , • and "aevuiiini-d: • aldehyde p e r o x i d e i The presence of these compounds Oh d e g r a d a t i o n show t h a t the rubber molecule c o n t a i n s a r e c u r r i n g double bond a f t e r each f o u r t h carbon and c o u l d be r e p r e s e n t e d by the f o l l o w i n g s t r u c t u r e Along w i t h the study of the s t r u c t u r e of the rubber m o l e c u l e j and the d e t e r m i n a t i o n o f i s o p r e h e as t h e b u i l d i n g u n i t * were many attempts t o s y n t h e s i z e a r t i f i c i a l rubber from i s o p r e n e i Although a g r e a t many attempts were'made, i t cannot be s a i d t h a t any of these, attempts were v e r y s u o o e s s f u l y and In 19io due to the h i g h p r i c e o f n a t u r a l r u b b e r i r e s e a r c h was s t a r t e d t o i n v e s t i g a t e t h e p o s s i b i l i t y -of p o l y m e r i z i n g butadiene;. T h i s work r e s u l t e d i n the p r o d u c t i o n of the Buna rubbers, whioh had p r o p e r t i e s t h a t made them a f a i r l y s u i t a b l e s u b s t i t u t e f o r n a t u r a l rubber. D u r i n g World War I , German chemists had l i t t l e success w i t h t h e i r s y n t h e t i c r u b b e r s . D u r i n g World War I I , s u p p l i e s o f n a t u r a l rubber were almost completely l o s t t o the A l l i e d rubber i n d u s t r i e s , and I t was imperative t o develop immed-i a t e l y a s u i t a b l e s y n t h e t i c rubber. Most of the r e s e a r c h was d i r e c t e d towards the g o a l of p e r f e c t i n g and p u t t i n g i n t o l a r g e s c a l e p r o d u c t i o n , GR-S (emulsion polymerized buta-diene-styrene) w i t h the r e s u l t t h a t a s a t i s f a c t o r y s u b s t i t u t e 3. f o r n a t u r a l rubber f o r most purposes was o b t a i n e d . The work on isoprene d u r i n g t h i s time was n e g l i g i b l e . 4. THEORY •3 I t was shown i n 1932 by FIsoher & H a r k i n s t h a t the absorbed f i l m between a hydrocarbon o i l and a sodium o l e a t e s o l u t i o n a t o . l M c o n c e n t r a t i o n i s monomolecular, w i t h the p o l a r groups o r i e n t e d toward the water, and the hydrocarbon group toward the o i l . T h i s o r i e n t a t i o n i s accompanied by a decrease i n f r e e energy and t h e r e f o r e i s the more s t a b l e " c o n d i t i o n . However, i t was found t h a t a t room temperature potassium l a u r a t e g i v e s a c l e a r s o l u t i o n i n water up t o 33% and potassium i a y r i s t a t e up t o 26%, These h i g h v a l u e s might be taken t o i n d i c a t e t h a t s o l i d soap may reduce I t s f r e e energy by going i n t o s o l u t i o n i n some other form than t h a t of s i n g l e molecules. In g e n e r a l , i t has been found t h a t most o f t h e soap d i s s o l v e d I s pre s e n t as aggregates, each o f which o o n t a l n a l a r g e number o f molecules. These aggregates are d e s i g n a t e d as soap inmtioelles. The g e n e r a l s t r u c t u r e of /these soap m i c e l l e s c o n s i s t s of three double l a y e r s o f soap •r molecules w i t h the p o l a r groups toward the water, and the o i l groups towards each o t h e r , w i t h a l a y e r of water between eaoh double l a y e r o f soap molecules . T h i s water l a y e r i s an I n t e g r a l p a r t o f the soap m i c e l l e r a t h e r than a s o l v e n t , and i s u s u a l l y r e f e r r e d t o as "bound water", i n c o n t r a s t t o the term f r e e water (water as a s o l v e n t ) . B e s i d e s b e i n g an e m u l s i f i e r , soap i s a l s o a s o l u b i l i z e r . i t has been f a i r l y c o n c l u s i v e l y shown t h a t when monomer i s added t o soap s o l u t i o n , t h a t i t i s s o l u b i l i z e d b e t w e e n t h e h y d r o c a r b o n e n d s o f t h e o r i e n t e d s o a p m o l e c u l e s . The soap m i c e l l e i s t h e p r o m i n e n t i n i t i a l l o c u s f o r p o l y -m e r i z a t i o n . H o w e v e r , i t i s n o t a l o c u s t h r o u g h o u t t h e p o l y m e r i z a t i o n s i n c e t h e p o l y m e r p a r t i c l e f o r m e d a d s o r b s a m o n o l a y e r o f s o a p m o l e c u l e s . T h i s c a u s e s a r a p i d d i s a p p e a r -a n c e o f t h e s o a p f r o m t h e m i c e l l e s , a n d h e n c e t h e m i c e l l e s t h e m s e l v e s seem t o c o m p l e t e l y d i s a p p e a r f r o m a f i v e p e r c e n t , s o l u t i o n a t a c o n v e r s i o n o f a b o u t t w e l v e p e r c e n t . A t l o w y i e l d s t h e p o l y m e r h a s b e e n shown t o c o n t a i n more monomer t h a n p o l y m e r a n d t h u s a f t e r t w e l v e p e r c e n t , y i e l d t h e m a i n l o c u s o f r e a c t i o n i s t h e polymer-monomer p a r t i c l e . The monomer d r o p l e t s w h i c h p e r s i s t a f t e r t h e soap m i c e l l e s h a v e d i s a p p e a r e d a r e n o t t h o u g h t t o a c t p r i m a r i l y a s l o c i o f r e a c t i o n , b u t r a t h e r a s r e s e r v o i r s o f monomer f r o m w h i c h monomer m o l e c u l e s d i f f u s e i n t o a l l o f t h e o t h e r l o c i . I n a f r e e r a d i c a l t y p e o f r e a c t i o n t h e m o l e c u l e s g r o w v e r y r a p i d l y — i n t h e o r d e r o f a f r a c t i o n o f a s e c o n d . I n o r d e r , t h e r e f o r e , t o e x e r t a n y c o n t r o l o v e r t h e s i z e o f t h e m o l e c u l e s i t m u s t be a p r o c e s s o f b a l a n c i n g c h a i n i n i t -i a t i o n s a n d c h a i n t e r m i n a t i o n . Many o f t h e m e r c a p t a n s w h i c h a r e e f f e c t i v e a s c h a i n i n i t i a t o r s a r e a l s o e f f e c t i v e i n c o n t r o l l i n g m o l e c u l a r w e i g h t t h r o u g h c h a i n t r a n s f e r , e . g . c h a i n i n i t i a t i o n R-5H + Ox-> R £ ° + HQ,0 R - S ° + C H A = p ^ C H = C H , - ^ R-S<Hr$=CH-CM° 6, • and c h a i n t e r m i n a t i o n CH3 CH 3 A n a l y s i s o f v a r i o u s polymers i n d i c a t e s t h e presence of one sulphur atom per molecule . A l s o i n polymers made by u s i n g t h i o g l y c o l i o a c i d and e ^ h y l t h l o g l y o o l a t e as m o d i f i e r s , i t I s found t h a t the r a t i o o f sulphur atoms t o c a r b o x y l or oarb e t h o x y l groups i s n e a r l y I 5 I . The exte n t o f m o d i f i c -a t i o n o b t a i n e d w i l l depend on the r a t e o f f o r m a t i o n o f mercaptyl r a d i c a l s by the o x i d i z i n g agent, the r a t e o f r e a c t i o n of the f r e e m e r c a p t y l r a d i c a l s w i t h the monomer moleoules, and the r a t e o f r e a o t i o n o f the growing polymer c h a i n w i t h mercaptans. D i f f u s i o n r a t e of the meroaptan i s important. As H a r k i n s has shown, the r e a o t i o n takes p l a c e e i t h e r i n the aqueous s o l u t i o n o r i n polymer-monomer p a r t i c l e formed by d i f f u s i o n from the o r i g i n a l emulsion monomer d r o p l e t . The main f u n c t i o n o f the meroaptan, a s i d e from i t s i n i t i a t i n g a c t i o n , i s to c o n t r o l t h e s i z e o f the polymer c h a i n . However, i t i s p l a i n t h a t even under the most f a v o r -able c o n d i t i o n s a wide v a r i a t i o n i n molecular weight w i l l be obt a i n e d . The major f a c t o r r e s p o n s i b l e f o r the wide • molec u l a r weight d i s t r i b u t i o n i s t h e v a r i a t i o n i n the con-c e n t r a t i o n o f the m o d i f i e r throughout the r e a c t i o n . At a co n v e r s i o n of 70% t h e r e i s approximately a t e n f o l d change In meroaptan c o n c e n t r a t i o n . Thus t h e molecular weight d i s t r i b u t i o n w i l l c h a n g e w i t h c o n v e r s i o n due t o t h e c h a n g e i n m o d i f i e r c o n c e n t r a t i o n d u r i n g t h e c o u r s e o f t h e r e a c t i o n . The r e a c t i o n t i m e w i l l a l s o a f f e c t t h e amount o f m o d i f i c a t i o n e s p e c i a l l y w i t h m e r c a p t a n s w h i c h h a v e a s l o w r a t e o f d i f f u s -i o n . R e a c t i o n t e m p e r a t u r e w o u l d a l s o be e x p e c t e d t o c h a n g e t h e p r o p e r t i e s o f t h e p o l y m e r due t o t h e c h a n g e o f r a t e o f r e a c t i o n , o f t h e r a t e o f d i f f u s i o n , a n d t h e t o t a l s o l u b i l i t y o f t h e m e r c a p t a n a s w e l l a s t h e o t h e r f a c t o r s . F o r a d i o l e f i n s u c h a s i s o p r e n e e a c h s t e p i n t h e p r o p -a g a t i o n may t a k e p l a c e i n one o f s e v e r a l d i f f e r e n t : w a y s . F o r t h e a d d i t i o n o f a f r e e r a d i c a l i t w o u l d be p o s s i b l e t o h a v e t h e f o l l o w i n g i n i t i a l s t e p s . CT/, , . 9^. ) c i s a n d t r a n s 1, 4 a d d i t i o n o (2} c i s a n d t r a n s 1, 4 a d d i t i o n 1, 2 a d d i t i o n 1, 2 a d d i t i o n " 3 , 4 a d d i t i o n 0 c v 3 /7 V C / / * = CrCH-CHz-* ff-6-CH^Cl4  ^ (6) 2, 4 a d d i t i o n o However, the tendenoy of the methyl group t o cause a d r i f t o f e l e c t r o n s away from i t s e l f i s w e l l known . We should expect, t h e r e f o r e , a c e n t r e o f e l e c t r o n d e n s i t y as I n d i c a t e d i n t he f o l l o w i n g e q u a t i o n . That t h i s I s the case has a l s o been shown by the D I e l s A l d e r r e a c t i o n w i t h a c r y l i c aldehyde on Isoprene and other s i m i l a r r e a c t i o n s S i n c e the f r e e r a d i o a l i s l o o k i n g f o r a c e n t r e Of e l e o t r o n d e n s i t y we should expect t h a t by analogy we c o u l d l a r g e l y e l i m i n a t e e quations 2, 3, 5, and $, A l s o i t has been shown t h a t i n the case of butadiene the amount of 1, 2 a d d i t i o n i s n e g l i g i b l e . By analogy a g a i n we should expect, t h e r e f o r e , the e l i m i n a t i o n o f e q u a t i o n 4. I t has been f r e q u e n t l y s t a t e d i n the l i t e r a t u r e t h a t isoprene i s b e l i e v e d t o add l a r g e l y 1 - 4, and the above t h e o r y i s advanced as an e x p l a n a t i o n of the tendency of isoprene t o add 1 - 4. 9 . EXPERIMENTAL WORK  PART I The e f f e c t o f o x y g e n f r o m t h e a i r on t h e r a t e o f p o l y m e r i z a t i o n h a s b e e n r e p o r t e d by v a r i o u s w o r k e r s f r o m t i m e A3 t o t i m e . We h a v e p r e v i o u s l y r e p o r t e d , t h a t i n t h e p o l y m e r i z a t i o n o f i s o p r e n e u s i n g H2O2 a s a n o x i d i z i n g a g e n t , t h a t b o t h y i e l d . a n d t h e i n t r i n s i c v i s c o s i t y v a r i e d w i t h t h e t i m e o f e x p o s u r e o f t h e s o a p - f e r r o u s s u l p h a t e - m e r c a p t a n m i x t u r e t o t h e a i r . B o t h t h e y i e l d a n d v i s c o s i t y c u r v e s w e r e f o u n d t o p a s s t h r o u g h a maximum. T h i s e f f e c t c o u l d be e x p l a i n e d b y — ( a ) t h e f o r m a t i o n o f s o a p p e r o x i d e s b y t h e a c t i o n o f o x y g e n o n t h e u n s a t u r a t e d p a r t s i n t h e s o a p m o l -e c u l e s ; (b) t h e o x i d a t i o n o f p a r t o f t h e m e r c a p t a n t o t h e d i s u l p h i d e a n d h e n c e l e s s m o d i f i c a t i o n w o u l d be o b t a i n e d ; (c) t h e a b s o r p t i o n o f o x y g e n i n t o t h e s o a p g e l t h u s i n c r e a s i n g t h e t o t a l amount o f O x i d i z i n g a g e n t . I n o r d e r t o d e t e r m i n e i f s o a p p e r o x i d e s w e r e f o r m e d , t h e method o f E . J . B e t t e r a n d A. D a v i d s o h n was u s e d . H o w e v e r , a l t h o u g h a s m a l l q u a n t i t y o f p e r o x i d e s w e r e f o u n d p r e s e n t i n i t i a l l y , t h e r e was no d e t e c t a b l e i n c r e a s e i n t h e s o a p p e r o x i d e v a l u e u p o n e x p o s u r e t o a i r f o r f o r t y e i g h t h o u r s a t 25° C. C o n f i r m a t i o n o f t h i s d a t a h a s p r e v i o u s l y b e e n p u b l i s h e d b y F.D. G u n s t o n e a n d T.P. H i l d i t c h who f o u n d n o i n c r e a s e i n p e r o x i d e v a l u e u p o n e x p o s u r e o f m e t h y l o l e a t e t o a i r a t 25° C. f o r p e r i o d s l e s s / O t h a n one h u n d r e d h o u r s . I.M. K o l t h o f f a n d I . K . M i l l e r h a v e shown t h a t t h e r e i s a m e a s u r e a b l e r a t e o f o x i d a t i o n o f 10. m e r c a p t a n i n s o a p s o l u t i o n t o t h e d i s u l p h i d e . T h e r e f o r e , i t i s c o n c l u d e d t h a t t h e o b s e r v e d i n i t i a l i n c r e a s e i n y i e l d i s due t o a c o m b i n a t i o n o f (b) a n d ( e ) , w h e r e a s , t h e e v e n t u a l d e c r e a s e o f y i e l d i s due t o t h e o x i d a t i o n o f a l a r g e p o r t i o n o f t h e m e r c a p t a n t o t h e d i s u l p h i d e a n d t h u s t h e amount o f c h a i n i n i t i a t i o n i s s l i g h t . I n o r d e r t o t e s t t h e v a l i d i t y o f t h e s e c o n c l u s i o n s i t seemed n e c e s s a r y t o t e s t t h e e f f e c t o f t h e d i s u l p h i d e s on p o l y m e r i z a t i o n , a nd dompare t h e e f f e c t o f t h e d i s u l p h i d e s w i t h t h e c o r r e s p o n d i n g m e r c a p t a n s . The compounds s y n t h e s i s e d i n t h i s c l a s s w e re n d i d o d e c y l d i s u l p h i d e , p h e n y l m e r c a p t a n a n d d i p h e n y l d i s u l p h i d e . D o d e c y l D i s u l p h i d e P r e p a r a t i o n o f d o d e c y l d i s u l p h i d e b y t h e m e t h o d o f F o r e a n d B o s t : Ten g r a m s o f d o d e c y l m e r c a p t a n was d i s s o l v e d i n b o i l i n g e t h y l a l c o h o l a n d s u f f i c i e n t a l c o h o l i c l e a d a c e t a t e was a d d e d s l o w l y t o e n s u r e c o m p l e t e p r e c i p i t a t i o n o f t h e y e l l o w l e a d d e r i v a t i v e . The p r e c i p i t a t e w a s d i g e s t e d one h o u r a n d f i l t e r e d h o t . The r e s i d u e was w a s h e d w i t h c o l d w a t e r , a nd t h e n w i t h s u c c e s s i v e p o r t i o n s o f h o t a c e t o n e a n d b o i l i n g e t h e r u n t i l no more s o l u b l e m a t e r i a l c o u l d be e x t r a c t e d . F i f t e e n g rams o f t h e l e a d s a l t w e r e s u s p e n d e d i n 500 m i s . o f h o t g l a c i a l a c e t i c a c i d , a n d a s l i g h t e x c e s s o f i o d i n e i n t h e same s o l v e n t was a d d e d d r o p b y d r o p . The s o l u t i o n was d i l u t e d w i t h w a t e r a n d c o o l e d , t h e n f i l t e r e d a n d w a s h e d w i t h c o l d w a t e r . The r e s i d u e was s h a k e n w i t h t h r e e l j j O m l . 1 1 . p o r t i o n s o f 20$ K I t o c o n v e r t t h e P b l 2 t o t h e s o l u b l e c o m p l e x K P b l r j . T h i s l a t t e r p a r t o f t h e p r o c e d u r e d o e s n o t w o r k w e l l s i n c e t h e r e s i d u e i s e x t r e m e l y r e s i s t a n t t o w e t t i n g b y w a t e r . H o w e v e r , t h e p r o d u c t c a n be c r y s t a l l i z e d w e l l f r o m g l a c i a l a c e t i c a c i d a n d s i h c e t h e P b l 2 i s r e l a t i v e l y i n s o l u b l e i t c a n be f i l t e r e d o f f . The s e c o n d r e c r y s t a l l i z a t i o n g i v e s l o n g w h i t e n e e d l e s o f t h e d i s u l p h i d e w i t h a v e r y s h a r p . m e l t i n g p o i n t o f 3 4 . 5 ° C. T h i s m e l t i n g p o i n t i s c o n s t a n t u p o n f u r t h e r r e c r y s t a l l i z a t i o n . P h e n y l M e r o a p t a n F i f t y g rams o f p h e n y l m e r o a p t a n w e r e p r e p a r e d b y r e d u c i n g e i g h t y f i v e grams o f b e n z e n e s u l p h o n y l c h l o r i d e w i t h two h u n d r e d grams o f t i n a n d f i v e h u n d r e d m i s . o f h y d r o -c h l o r i c a c i d . The m e r o a p t a n v/as s t e a m d i s t i l l e d , e x t r a c t e d w i t h e t h e r , a n d a f t e r d r i v i n g o f f t h e e t h e r was d i s t i l l e d a t a t m o s p h e r i c p r e s s u r e a t 1 6 6 - 1 7 0 ° C. D i p h e n y l d i s u l p h i d e D i p h e n y l d i s u l p h i d e w a s p r e p a r e d b y e v a p o r a t i n g f i v e g r a m s o f p h e n y l m e r o a p t a n w i t h a f e w m i s . o f d i l u t e ammonia an d u p o n c o o l i n g c r y s t a l s o f d i p h e n y l d i s u l p h i d e w e r e o b t a i n e d , a n d a f t e r r e c r y s t a l l i z a t i o n h a d a m e l t i n g p o i n t o f 6 1 ^ 1 ° C. 12, RESULTS; E a c h m o d e l was p r e p a r e d b y d i s s o l v i n g 4*5 grams o f R.R.C. s o a p a n d 0.1 grams o f f e r r o u s s u l p h a t e i n two h u n d r e d m i s . o f h o t w a t e r . The o x i d i z i n g a g e n t , m o d i f i e r , a n d one h u n d r e d grams o f i s o p r e n e w e r e a d d e d a f t e r t h e s o a p s o l u t i o n h a d b e e n c o o l e d t o 30° C. P o l y m e r i z a t i o n was a c c o m p l i s h e d b y end o v e r end r o t a t i o n o f t h e b o t t l e s a t a r a t e o f e i g h t e e n r e v o l u t i o n s p e r m i n u t e i n a c o n s t a n t t e m p e r a t u r e b a t h a t 45° C. I n a l l c a s e s l i s t e d b e l o w t h e t i m e o f p o l y m e r i z a t i o n was t w e n t y - f o u r h o u r s . TABLE I M o d i f i e r O x i d i z i n g A g e n t % Y i e l d .2 g- C 1 2 H 2 5 S H 6 m i s . o f ; ) % H 2 0 2 70 tt tt tt tt n 72 tt tt tt tt t» 73 .2 g. G 1 2 H 2 5 S " S C 1 2 H 2 5 » tt tt 10 tt tt ft ft ft 10 >? ft tt tt tt 9 .2 g. C 6 H $ S H tt ft rt n e g l i g i b l e tt tt tt tt tf tt n tt tt n tt .2 g. C 6 H 5 S - S C 6 H 5 tt tt tf tt tt tt tt tt tt tt tt tt tt tr tt tt 13. I t seems p r o b a b l e t h a t p h e n y l m e r o a p t a n i s a p o o r i n i t i a t i n g a g e n t f o r p o l y m e r i z a t i o n s i n c e i t i s t o o e a s i l y o x i d i z e d t o t h e d i s u l p h i d e a s i s t h e c a s e w i t h t h e l o w e r a l i p h a t i c members. The f a c t t h a t n - d i d o d e c y l d i s u l p h i d e i s u n r e a c t i v e b e a r s o u t o u r p r e v i o u s c o n c l u s i o n s i 14. PART I I S i n c e t h e m e c h a n i s m o f p o l y m e r i z a t i o n i s b e l i e v e d t o p r o c e e d t h r o u g h f r e e r a d i c a l f o r m a t i o n , i t was d e c i d e d t o t r y v a r i o u s d i a z o t h i o e t h e r s a s i n i t i a t i n g a g e n t s w h i c h , a c c o r d i n g t o T.B. R e y n o l d s , decompose b y t h e r m a l d e c o m p o s i t i o n a c c o r d i n g t o t h e f o l l o w i n g e q u a t i o n : O r i g i n a l l y t h e m e r c a p t a n s u s e d i n c o u p l i n g , n a m e l y , t h i o n a p h t h o l a n d p a r a m e t h y l p h e n y l m e r c a p t a n w e r e p r e p a r e d a s i n d i c a t e d b e l o w . H o w e v e r , a l l f i n a l t e s t s w e r e made w i t h m e r c a p t a n s o b t a i n e d f r o m E a s t m a n K o d a k Co. T h i o /3 N a p h t h o l S o d i u m n a p h t h a l e n e s u l p h o n a t e was p r e p a r e d b y t h e m e t h o d o f F i e s e r , a n d t h e s o d i u m s a l t was c o n v e r t e d t o t h e c o r r e s p o n d i n g s u l p h o n y l c h l o r i d e b y h e a t i n g t h e d r y s o d i u m s,:. s a l t w i t h p h o s p h o r o u s p e n t a c h l o r i d e a t 150° C. The p r o d u c t was r e c r y s t a l l i z e d f r o m c h l o r o f o r m . The s u l p h o n y l c h l o r i d e t h u s o b t a i n e d was r e d u c e d w i t h t i n a n d h y d r o c h l o r i c a c i d . The t h i o & n a p h t h o l was s t e a m d i s t i l l e d a n d r e c r y s t a l l i z e d f r o m a l c o h o l . M e l t i n g p o i n t 82 1° C. P - T h i o O r e s o l S o d i u m p - t o l u e n e s u l p h o n a t e was p r e p a r e d b y t h e m e t h o d o f F i e s e r , c o n v e r t e d t o t h e a c i d c h l o r i d e a s a b o v e , a n d t h e n r e d u c e d t o t h e c o r r e s p o n d i n g m e r c a p t a n . The m e r c a p t a n 15. was r e c r y s t a l l i z e d f r o m a l c o h o l . M e l t i n g P o i n t £- 1° C. D i a z o T h i o E t h e r s A t y p i c a l p r e p a r a t i o n o f a d i a z o t h i o e t h e r c o n s i s t e d o f d i s s o l v i n g 0.1 m o l e s o f a n a m i n e i n one h u n d r e d m i s . o f v3.0 N a c i d . The t e m p e r a t u r e o f t h e a c i d s o l u t i o n o f t h e a m i n e was k e p t a t 0° C. t h r o u g h o u t t h e d r o p w i s e a d d i t i o n o f a n a q u e o u s s o l u t i o n o f s o d i u m n i t r i t e . The a d d i t i o n o f s o d i u m n i t r i t e was c o n t i n u e d u n t i l a p e r m a n e n t r e a c t i o n o f n i t r o u s a c i d w i t h s t a r c h i o d i d e p a p e r was o b t a i n e d . The d i a z o t i z e d s o l u t i o n was t h e n f i l t e r e d w i t h d e c o l o r i z i n g c a r b o n t h r o u g h a c h i l l e d B u c h n e r i n t o a c h i l l e d f l a s k . C o u p l i n g was. a c c o m p l i s h e d b y s l o w l y a d d i n g t h e d i a z o t i z e d s o l u t i o n w i t h c o n s t a n t s t i r r i n g t o a n a l k a l i n e i c e s o l u t i o n o f t h e m e r o a p t a n c o n s i s t i n g o f s l i g h t l y more t h a n 0.1 m o l e s o f m e r o a p t a n i n a s o l u t i o n o f f o u r h u n d r e d m i s . o f 2.0 N s o d i u m h y d r o x i d e a n d t w e n t y g r a m s o f s o d i u m c a r b o n a t e . The r e s u l t i n g y e l l o w s o l i d ' w a s f i l t e r e d o f f a n d d r i e d u n d e r vacuum. T h i s - p r o c e d u r e w o r k e d w e l l f o r m o s t o f t h e d i a z o t h i o e t h e r s a t t e m p t e d , h o w e v e r , o i l s w e r e o b t a i n e d when u s i n g p h e n y l m e r o a p t a n , a n d h e n c e was u n s a t i s f a c t o r y f o r t h i s p a r t i c u l a r m e r o a p t a n . The r a t e o f d e c o m p o s i t i o n o f some o f t h e d i a z o e t h e r s was m e a s u r e d b y o b s e r v i n g t h e r a t e o f e v o l u t i o n o f n i t r o g e n f r o m a s o l u t i o n o f t h e e t h e r i n one h u n d r e d m i s . o f b u t y l p h t h a l a t e . The r a t e s o f d e c o m p o s i t i o n o f t h e d i a z o e t h e r s i s g r e a t l y i n f l u e n c e d b y t e m p e r a t u r e , a t w e n t y d e g r e e d e c r e a s e i n t e m p e r a t u r e i n c r e a s e s t h e i n d u c t i o n p e r i o d a n d 16. t h e h a l f l i f e p e r i o d b y a p p r o x i m a t e l y a f a c t o r o f s e v e n f o r p - m e t h y l b e n z e n e d i a z o t h i o / 3 n a p h t h o l . The t e m p e r a t u r e f o r d e c o m p o s i t i o n was c h o s e n a t 6 5 ° C. s i n c e i t p r o v i d e s a c o n v e n i e n t r a t e o f r e a c t i o n f o r m o s t o f t h e e t h e r s . A f t e r t h e i n d u c t i o n p e r i o d i s o v e r t h e d e c o m p o s i t i o n c l o s e l y p a r a l l e l s a f i r s t o r d e r r e a c t i o n . R e s u l t s f o r t h e decomp-o s i t i o n o f v a r i o u s d i a z o e t h e r s a p p e a r i n T a b l e s I I , I I I , a n d I V . ( P a g e s 17, 18, & 19) 17. TABLE II Decomposition of p-methyl benzene diazo thio/3-naphthol at 65° C. Sample #1 Sample #2 Time i n Sees. Mis. of N 2 Time i n Seos. Mis. of N 2 0 0.0 0 0.0 1560 1.0 1620 1.0 1920 2.0 2000 2.0 2200 2.0 2295 5.0 2400 4.0 2520 4.0 2572 5.0 2715 5.0 2720 6.0 2900 6.0 2900 7.0 2070 7.0 2032 8.0 2220 8.0 2210 ,9.0 2260 9.0 2227 10.0 2500 10.0 2872 15.0 4100 15.0 4582 20.0 4760 20.0 5210 25.0 5485 23.0 6100 50.0 6240 50.0 7020 55.0 7250 25.0 8100 40.0 8255 40.0 9225 45.0 9660 45.0 11020 50.0 Total 71.5 Total 70.0 Negleoting the induction period the time for half decomp-osition for p-methyl benzene diazo thio •d-naphthol in one hundred mis. of butyl phthalate i s 821:1 minute at 65° C« 18. TABLE III Decomposition of p-methyl benzene diazo thio p toluene at 6 5 ° 0 . Sample #1 Sample #2 Time i n Sees. Mis. of N 2 Time in Sees. Mis. of N2 0 0.0 0 0.0 9?0 1.0. 962 1.0 1228 5.0 1216 5.0 1415 5.0 1597 5.0 1602 7.0 1570 7.0 1770 9.0 1762 9.0 1952 11.0 2000 15.0 2286 15.0 2240 16.0 2520 18.0 2590 20.0 5086 24.0 5052 25.0 5527 28.0 .:> 3595 50.0 4545" 54.0 4278 55.0 5020 58.0 - 5095 40.0 Total 58.2 Total 60.0 Neglecting the i n i t i a l induction period, the time for half decomposition of p-methyl benzene diazo thio p-toluene i s 42 i 1 minutes in one hundred mis. of butyl phthalate at 65° 0. 19. TABLE IV Sample fl Sample #2 Time, in Sees. Mis. of N 2 Time in Seos. Mis. of Ng 45 0 0.0 0 0.0 4590 1.0 4520 1.0 7520 5.0 7400 6.0 8140 7.0 8510 9.0 9650 11.0 9675 12.0 12150 17.0 11555 16.0 15200 19.0 15200 20.0 14120 21.0 15700 25.0 17520 27.0 18680 50.0 21600 55.0 22040 55.0 Total 56.1 Total 58.9 Neglecting the i n i t i a l induction period the time for half decomposition of p-bromo benzene diazo thio p-toluene in one hundred mis. of butyl phthalate at 65° C. i s 212£"5 minutes. 25. Measurements on the rates of decomposition of the diazo thio ethers were discontinued since the rates of decomposition were found to be influenced by surfaoe area. Both the induction period and the time for half decomposition were found to be less when the decomposition was carried out in a vessel in which the surfaoe area had been greatly increased by packing with glass. However, since the rates of decomp-osition previously recorded were measured under similar conditions they do afford a relative comparison of the s t a b i l i t i e s of the ethers. A relative comparison of the s t a b i l i t y of these ethers should also be obtained from the rates of polymerization obtained by using these ethers as i n i t i a t i n g agents. This comparison should at least be valid for any one series, and may be valid from one seried to another. Following are typical tables of the results obtained using diazo thio ethers as i n i t i a t i n g agents. The amount of the particular diazo thio ether used i n a model was based on a weight equivalent to one gram of p-methyl benzene diazo thio3 -naphthol. Preparation of Model Each model was prepared by dissolving 4.5 grams of R.R.C. soap in two hundred mis. of water by heating. After cooling the soap solution to 25° C , one hundred grams of isoprene containing the dissolved diazo ether was added. Polymerization was accomplished by end over end rotation of the bottles at a rate of eighteen revolutions per minute 24. at a temperature of 45° C. T A B L E V i n i t i a t i n g Agent Time of Yield Gel Polymerization % % 1.00 g. p-CHj-C 6H4-N=N-S-C 1QRrj 9 hours 70 68 68 000 1.23 g. p-Br -C ^H4-K=N-S-C 1QH«y 24 hours 22 21 18 0 0 1.68 g. p-N02-C6H4-N=N-S-C1oH7 24 hours ^ 5 ^ 3 < 5 000 1.08 g. o-N02-C6H4-N=N-S-CioH7 24 hours ^ 3 ^ 5 <5 000 .87 g. P-CH3-C 6H4-NZN-S-C 6H4-CH3 $ hours 88 ?1 90 0 0 0 1.08 g. p-Br-C 6H4-N=N-S-G 6H4-CH3 24 hours 36 36 38 000 .20 g. CH3-C6H4SH and 6 mis. of ^ 3 % H 20 2 24 hours 000 .20 g. - C 1 0 H 2 S H and 6 mis. of 3% H 20 2 24 rhours 000 In order to determine i f a valid comparison from one series to another of the diazo ethers oould be made, the rate of polymerization with p thio cresol a n d ^ Naphthyl mercaptan was tested. Both gave negative results as was the case with the phenyl mercaptan previously mentioned, and the reason for lack of iniation i s probably the same. 2$. TECHNIQUES Product Yields The yields calculated i n this thesis were based on the total solids content, and a correction was made for the soap content and any other solids present. Twenty to thirty grams were sampled into a weighing bottle and weighed rapidly to milligram accuracy. After the sample was dried In a drying oven (60° C.)itwas reweighed, and from this the total yield can be calculated. Preparation of the Anti Oxidant i n order _to prepare _a suitable colloidal suspension of P.B.N.A. (phenyl naphthylamine) the following formula was added directly to a Waring Blendor: HgO 100 mis. . .. R.R.C.. Soap 1 2.0 g. P.B.N.A. 20.0 g. Five minutes whipping i n the blendor i s sufficient to form a suitable suspension. If the yield i s low i t i s necessary to strip the latex of excess isoprene, otherwise coagulation of the P.B.N.A. results when i t comes in contact with the latex, and a fine precipitate of P.B.N.A. throughout the crumb i s not obtained. Precipitation of the Latex Precipitation was achieved by adding brine-acid solution of the following formula: 2 6 . H20 6,000 mis. NaCl 367 g. 10.5 mis. Sufficient brine-acid solution i s added to the latex (containing sufficient P.B.N.A. to total 1.25% of the dried polymer) until the latex coagulates and a solution of pH 4 - 4 . 5 results. For very low yields i t i s necessary to precipitate the sample with isopropyl alcohol which breaks the emulsion by dissolving the soap. Any precipitate obtained in this way i s polymer only. Kolthoff and Medalia in October, 1945, summarized the theory and method of determination of the gel content of a polymer. T n e Harris cage was used here, for the dtermin-ation of a l l gel contents. A sample of from o.l to 0.2 grams of the polymer was cut into small pieces in order to f a c i l i t a t e solution, and then the sample was placed in the cage. The cage was suspended in a beaker containing one hundred mis., of toluene in such a manner that i t was completely immersed without touohigg any. surface. This was now placed in a desiccator containing toluene in the bowl, and was l e f t for a period of at least forty-four hours away from the actinic light. The sol part of the rubber w i l l disperse throughout the toluene during this time, while the swollen gel w i l l remain inside the cage. Determination of pel Content 27. On completion of the s t a n d i n g time, the cage was removed c a r e f u l l y from t h e beaker and suspended i n a i r f o r a few minutes to evaporate o f f the m a j o r i t y of the s o l v e n t . The cage was f i n a l l y d r i e d i n an oven at 60° C. The percentage g e l content was c a l c u l a t e d as f o l l o w s : Let X be the weight of the empty cage Let Y be the weight o f the cage p l u s the sample Le t Z be the weight of the oage p l u s the d r i e d g e l Y - Z x 100 Percent s o l = -4~ 1 Y - X Percent g e l • 100 - percent s o l The one percent was added to the s o l t o take i n t o account the amount of s o l trapped i n the swollen g e l . T h i s c o r r e c t i o n i s f a i r l y a c c u r a t e f o r s m a l l amounts of g e l , but a h i g h e r c o r r e c t i o n f a c t o r i s needed f o r high g e l . content polymers. 28. CONCLUSIONS I f the mechanism of p o l y m e r i z a t i o n does proceed through the f o r m a t i o n of f r e e r a d i c a l s and terminate through c h a i n t r a n s f e r , then i t should be p o s s i b l e t o s y n t h e s i z e a product that would d i s s o c i a t e or decompose i n s o l u t i o n to p r o v i d e a s u i t a b l e c o n c e n t r a t i o n of f r e e r a d i c a l s . Such pro d u c t s were obtained i n the p r e p a r a t i o n of p-methyl benzene d i a z o t h i o -naphthol and p-methyl benzene d i a z o t h i o p - t o l u e n e . I t has been p r e v i o u s l y shown i n t h i s paper t h a t a good r a t e of p o l y m e r i z a t i o n c o u l d be o b t a i n e d simply be adding one of the above compounds t o e m u l s i f i e d i s o p r e n e . Thus by the f o l l o w i n g d i s s o c i a t i o n of the compounds two f r e e r a d i c a l s are obtained, and s i n c e there are no other compounds pr e s e n t , i t i s c o n c l u s i v e l y shown t h a t i n i t i a t i o n does proceed through a f r e e r a d i c a l mechanism as proposed e a r l i e r i n t h e t h e o r y p a r t of t h i s paper. I t has a l s o been ^ o i shown t h a t the presence of groups such as Br, N ^ Q , i n t h e amine p a r t of the molecule g r e a t l y reduces the e f f e c t i v e -ness of the d i a z o t h i o e t h e r . The e t h e r s formed by c o u p l i n g w i t h t h i o / 3 naphthol are more s t a b l e than those formed by c o u p l i n g w i t h p - t h i o c r e s o l . The g r e a t e r s t a b -i l i t y of the former c o u l d be a t t r i b u t e d t o the g r e a t e r resonance p o s s i b l e i n the naphthalene nucle u s as compared 29. t o the benzene nucleus. I n a d d i t i o n the i n t r o d u c t i o n of a n i t r o group i n the para or o r t h o p o s i t i o n of the amine p a r t c o n t r i b u t e s s t r o n g l y t o other resonance p o s s i b i l i t i e s . S i m i l a r l y the haolgens i n the ortho or para p o s i t i o n s of the amine p a r t c o n t r i b u t e t o o t h e r resonance p o s s i b i l i t i e s . However, i n the l a t t e r case t h e i n d u c t i v e and resonance e f f e c t s are opposed and the o v e r a l l c o n t r i b u t i o n t o r e s -onance would be expected to be much l e s s . In the case of the methyl group i n the ortho or para p o s i t i o n of the amine p a r t there are no new p o s s i b l e resonance s t r u c t u r e s of energy contents which are s i m i l a r . T h e r e f o r e , t h e o r e t i c a l c o n s i d e r a t i o n s would l e a d us t o the c o n c l u s i o n t h a t the p-methyl d e r i v a t i v e would d i s s o c i a t e more r e a d i l y t h a n the p-bromo and the l a t t e r i n t u r n more r e a d i l y than the 0 - , or p - n i t r o d e r i v a t i v e s . 10 (1 (2 (3 (4 (5 (6 (7 (8 (9 BIBLIOGRAPHT F i e s e r , L.F., "Experiments i n Organic Chemistry" P.136-141, Heath (1941) F i e s e r , L.F., "Experiments i n Organio Chemistry" P.142-143, Heath (1941) F i s c h e r , E.K., and H a r k i n s , W.D., J . Phys, Chem. i l , 98 (1932) Fore, D. and Bost, R.W.j - J . Am. Chem, Sao. Sg, 2537 (1937) Gunstone, T.P., and H l l d i t o h , J.P., - Chem. S o c , 1022-23 (1946) H a r k i n s , W.D,, J . Am. Ghem. Soc. 1428 (1947) H a r k i n s , W.D., Mattoon, H.W., and C o r r i n , M.L.* GR-382 Holmes, H.L., A l c o c k , K., Demianlw, D.G., Robinson, J.W., Rooney, C.E.S., and Sundberg, F.A., Can, J . Res. B,. 26: 248-255 (1?48) K o l t h o f f , J.M, and H a r r i e s , W.E...,. CR-425 (10) Kolthoff, I,M, and Miller», I*E,, CR-206 (11) Kblthoff, I,M. and Medalia, J., Report LXZI ^ Deter-mination of Gel i n GR*S" University of Minnesota, October 1 5 , (1945) (12) Longfield, j * , Blades* H i , and Sivertz, C*, OSR-4S (13) MacLean, H. ,. Barton, G>M,, Grnnlund, J* and Johnson, A.L.,.CR— (14) Snyder, H i R . and Wall, F , T , * CR-66 (15) Snyder, H.R*, Wall, F.T** Stewart, J.M., Alien R.i., Deaborn, R.J. and Sands, G.D,, CR-310 

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