MELTING AND CRYSTALLIZATION OF POLY(L-LACTIC ACID) AND POLY(ETHYLENE OXIDE) BINARY MIXTURE

The effects of mixing poly(ethylene oxide) (PEO) on the melting and crystallization process of poly(L-lactic acid) (PLLA) were studied by DSC, polarized microscope and wide angle X-ray diffraction (WAXD). Melting point (T(m)) depression of PLLA in the mixtures crystallized from the melt occurred with increasing PEO content but it did not occur in the mixtures crystallized from chloroform solution. T(m) of PEO also decreased with increasing PLLA content. The ringed spherulite is formed in the binary mixture although non-ringed spherulite is formed for pure PLLA and PEO crystallized from the melt. In the observation of the ringed spherulite during heating, the field of vision under the microscope only changed to be slightly dark above T(m) of PEO without changing the pattern of the spherulite. The result of WAXD leads to an idea that co-crystallization of PLLA and PEO molecule does not occur in the melt-crystallization and the ringed spherulite is made of PLLA and PEO lamella.