Synthesis of branched poly(lactic acid) bearing a castor oil core and its plasticization effect on poly(lactic acid)

Abstract

Branched poly(lactic acid) was synthesized by ring-opening polymerization of lactide using castor oil as an initiator. The structure of the branched polymer was confirmed by 1H nuclear magnetic resonance spectroscopy. The molecular weight of the branched polymer increased linearly as a function of the feed ratio of lactide and castor oil. The thermal properties of the branched polymer were evaluated using differential scanning calorimetry and were compared with those of linear poly(L-lactic acid) (PLLA). A blended film of the branched polymer and PLLA was prepared by hot pressing at 175 °C. A content of 5 wt% of the branched polymer was sufficient to increase the strain at break. Thermomechanical analysis of the blended film revealed a decrease in the initial elastic modulus with addition of the branched polymer. The thermal and dynamic mechanical properties of the film were examined, and the crystalline morphology of the film was examined by polarized light microscopy. Branched poly(lactic acid) was synthesized by ring-opening polymerization of lactide using castor oil as initiator. The blended film of the branched polymer and poly(L-lactic acid) was prepared by the hot-press method at 175 °C. Only a small amount of the branched polymer was enough to plasticize poly(L-lactic acid). The thermal and dynamic mechanical properties of the film were examined in detail, and the crystalline morphology of the film was observed using a polarized microscope.