Effects of molecular weight on the melting and crystallization of poly(L-lactic acid) in a mixture with poly(ethylene oxide)

The melting and crystallization behavior of poly(L-lactic acid) (PLLA) of different molecular weight (MW=2000, 66000, and 152000) in the binary mixture with poly(ethylene oxide) (PEO) of the different molecular weight (MW=3000, 100000, and 5000000) was studied by DSC, wide angle X-ray diffraction measurement and optical microscopy. Melting and crystallization process of PLLA depends on molecular weights of PLLA and PEO. Melting temperature (T-m) of the low molecular weight PLLA decreased drastically below the weight fraction of PLLA 0.2. T-m of high molecular weight PLLA decreased with decreasing PLLA in the mixture with low molecular weight PEO, while drastic decrease did not occur in the mixture with high molecular weight PEO. Temperature change of the morphological features of PLLA in thr binary mixture depends on the molecular weight of PLLA and weight fraction of PEO.