Spectroscopic analysis on cold drawing-induced PLLA mesophase

By cold drawing the amorphous PLLA sample at 65 °C (just above the glass transition temperature of PLLA), a set of uniaxially oriented samples with various draw ratios was prepared. The mesomorphic ordering and chain orientation in PLLA mesophase induced by the cold drawing process was examined by the WAXD and polarized FTIR techniques. Of note, it is interesting to find that the characteristic backbone vibration mode of PLLA mesophase around 918 cm−1, which has been firstly identified by Stoclet et al. in previous study [Macromolecules 2010, 7228-7237], actually demonstrates a symmetrical peak shifting with increasing the draw ratio. By considering the WAXD data, the correlation between the peak positions for this characteristic backbone vibration mode (located around 918-921 cm−1) that related to the chain conformation and the distance of interchain packing in PLLA mesophase obtained at various draw ratios was revealed.