Mesophase formation and its thermal transition in the stretched glassy polylactide revealed by infrared spectroscopy

The structural development in the glassy polylactide during stretching and subsequent heating has been investigated by Fourier transform infrared spectroscopy. It is indicated that only when molecular chains in the amorphous phase approach their finite extensibility beyond a critical strain of about 1, accompanied by remarkable conformational ordering, can cohesive mesophase with certain molecular ordering be brought out to trigger strain-induced crystallization. Upon heating cohesive mesophase endures melting during glass transition region where an endothermic peak is observed, and the extent of melting relies on its initial thermal stability and is in particular affected by the subsequent advent of strain-induced crystallization.