Obtaining aliphatic branched polycarbonates via simple copolymerization of trimethylene carbonate with cyclic carbonate containing pendant ester groups

Different possibilities for obtaining branched, functional carbonate copolymers are presented in this study. Copolymers were synthesized according to the ring-opening polymerization (ROP) of the cyclic carbonate monomers, containing pendant ester groups. As an example, we chose copolymerization of ethyl 5-methyl-2-oxo-1,3-dioxane-5-carboxylate (MTC-Et) with trimethylene carbonate (TMC), using zinc (II) and lanthanum (III) acetylacetonates as ROP initiators. The transesterification processes of ester groups in pendant, short chains, appearing during conducted copolymerization, led to the establishment of two different fractions: first-branched and high molecular weight fraction and second-linear and low molecular weight. The content of this high-molecular-weight fraction increased with both: the amount of MTC-Et in started reaction mixture and the time of conducted copolymerization. Reactivity constants in studied reaction were determined. It was possible to obtain the copolymer fraction (ca. 30%) with molecular weight of up to a million g/mol, with a highly branched chain microstructure using lanthanum (III) acetylacetonate as initiator. Conclusions were based on detailed NMR analysis, determining microstructure of the copolymer chains and additionally on GPC and DSC measurement. (C) 2016 Wiley Periodicals, Inc.