Poly(D-lactic acid-b-L-lactic acid)의 결정화거동 및 열적 특성

초록

A stereocomplex of poly(lactic acid) (PLA) from the opposite enantiomeric configurations of the L and D forms has higher thermal resistance and mechanical properties than poly(L-lactic acid) (PLLA), which may overcome the problems with the low melting temperature of PLLA when used as a commercial fiber. In this study, the crystallization behavior and thermal properties of poly(D-lactic acid-b-L-lactic acid) (PDLLA) block copolymer (50:50, w/w) were characterized by differential scanning calorimetry (DSC), dynamic mechanical analysis, and wide angle X-ray diffraction (WAXD) analysis. DSC showed that the melting temperature of the stereocomplex crystal was approximately 215 oC, which was much higher than that of homo PLLA (~168°C). The equilibrium melting temperature and stability parameter of PDLLA obtained from the Hoffman-Weeks plot was 230 oC and 0.44, respectively. Compared to the WAXD peaks of the α-form crystal of PLLA, additional peaks were observed for PDLLA at 11.9 o, 20.8 o, and 23.6 o 2θ arising from the D,L-stereocomplex crystal of PLA. The crystallization behaviors of PDLLA and PLLA during the heating and cooling processes from the melt-quenched state and from the molten state, respectively, were compared using the WAXD curves obtained from a synchrotron X-ray source. The effects of annealing of both PLLA and PDLLA films at different temperatures on the crystal formation were also examined.

키워드