Transcrystalline structures of poly(l-lactide)

Poly(l-lactide) (PLLA) film containing transcrystalline (TC) structures can easily be obtained by placing PLLA films melted between two poly(tetrafluoroethylene) (PTFE) sheets, followed by isothermal crystallization at 122 °C. The fine structures of the PLLA-TC film were studied by various structural techniques such as X-ray diffractometry, optical microscopy and transmission electron microscopy. We also examined the purification effect upon the morphology of PLLA-TC film. The formation of the TC structures revealed that one-dimensional spherulitic growth occurred from the assembling impurities as nucleation agent near the PTFE substrate in the heterogeneous nucleation system. We found that the b-axis of PLLA crystal was parallel to the lamellae growth direction confirmed using X-ray diffraction. The precipitated PLLA film crystallized in a similar process exhibited scanty TC textures, suggesting that the existence of impurity in the PLLA sample was an important factor for the formation of those structures.