HIGH-PRESSURE CRYSTALLINE OF POLY(L-LACTIC ACID) IN A BINARY MIXTURE WITH POLY(ETHYLENE OXIDE)

The effect of pressure on the melting and crystallization behavior of pure poly(L-lactic acid) (PLLA) and PLLA in the semi-miscible binary mixture with poly(ethylene oxide) (PEO) was studied by high pressure DTA up to 250 MPa. A high pressure-crystallized mixture was studied by DSC, polarized microscope and wide-angle X-ray diffraction (WAXD). Pressure dependence of the melting temperature (dT(m)/dP) of pure PLLA determined by high pressure DTA was 0.173 K MPa-1 which is slightly larger than that of PEO (0.15 K MPa-1). In cooling from the melt under high pressure, pure PLLA did not crystallize above 100 MPa, but in a mixture with PEO, the crystallization of PLLA occurred even at 200 MPa. The crystallization of PLLA under high pressure is discussed as due to increased interactions between PLLA molecules at elevated pressure.