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UBC Theses and Dissertations

Living and immortal polymerization of cyclic esters with a dinuclear indium catalyst Xu, Cuiling


The dinuclear indium catalyst [(NNO)InCl]₂(μ-OEt)(μ-Cl) (30), previously reported to be highly active and living in the ring-opening polymerization (ROP) of lactide (LA), was synthesized via a previously published procedure and is studied to be active for the ROP of β-butyrolactone (BBL), ε-caprolactone (CL) and allyl-β-butyrolactone (fBL). A series of diblock copolymers PLLA-b-PDLLA were synthesized for the first time and their thermal properties were studied. A series of triblock copolymers PLLA-b-PDLLA-b-PLLA/PDLA were synthesized for the first time. Studies on the polymerization of BBL by 30 reveal that it is highly solvent dependent and the rate is first order in BBL and catalyst concentration. The activation parameters were obtained from an Eyring plot. The polymerization is controlled, providing PHB with molecular weights in agreement to theoretical values up to 300 kDa in narrow distribution. Triblock copolymers PLLA-b-PHB-b-PDLA were synthesized via the sequential addition technique. Polymerization of CL by 30 showed an unusual slower rate than LA. Copolymers of allyl-β-butyrolactone with LA and BBL were made, supporting the feasibility of incorporating functionality into pendent groups of polyesters with this catalyst. The catalyst 30 is capable of immortal polymerization of LA and BBL with high loading of monomers and alcohols ([BBL]:[30]:[ROH] = 10000:1:100), providing polymers with molecular weights in well agreement with calculations inverse to the total amount of 30 and alcohols. The tacticity of polymers was not affected by the addition of ethanol. Poly(ethylene glycol) monomethyl ethers with molecular weights of 350 Da and 5000 Da were used as chain transfer agent to synthesize PEG and polyester block copolymers via iROP for the first time. Nanoparticles of PEG₁₁₄-b-PLLA₂₀₀ and PEG₁₁₄-b-PLLA₁₀₅ were made through nanoprecipitation and thin film rehydration/dialysis methods.

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