Surface-induced anisotropic chain ordering of polycarprolactone on oriented polyethylene substrate: Epitaxy and soft epitaxy

Studies on heteroepitaxy of polymers mostly dealt with the resulting mutual orientation relationship of the involving polymer pairs. The molecular dynamics during the expitaxial crystallization process of a polymer was, however, not concerned so far. To disclose the expitaxial crystallization process of polymers on a molecular scale, the structure evolution of polycarprolactone (PCL) in the molten state on highly oriented polyethylene (PE) substrate was followed by time-resolved Fourier transform infrared spectroscopy and wide-angle X-ray diffraction (WAXD). The results clearly indicate the existence of surface-induced anisotropic chain ordering of PCL in its molten state on highly oriented PE substrate, i.e., the occurrence of soft epitaxy. These ordered PCL chain segments in turn initiate the epitaxial crystallization of PCL on highly oriented PE substrate during the subsequent cooling process.