Biodegradable polyesters based on star-shaped lactic acid oligomers

Catalytic polymerization of ε-caprolactone and copolymerization of maleic anhydride and propylene or ethylene oxide carried out in the presence of star-shaped L-lactic acid oligomers were studied. The analysis of the reaction products by means of GPC, MALDI ToF and 1H NMR show that the applied processes allowed to combine oligomers with polyesters produced by ring opening polymerization and obtain a new type of lactic acid copolymers of relative molar masses in the range 15-60 kg/mol. DSC studies revealed that the formed polyesters segments were fully or partially miscible with poly(lactic acid) core causing the reduction of its glass transition temperature. Selected copolymers were subjected to enzymatic degradation, which indicated that all of these compounds underwent partial decomposition. An analysis of weight loss showed, however, that the degradation occurred more slowly than in the case of poly(lactic acid) of similar molar masses and chain architecture.