Abstract: The phase transition of quench-induced mesophase and deformed mesophase which was prepared by stretching the quench-induced mesophase during heating and isothermal annealing process was studied by in situ synchrotron radiation WAXD. The results show that though the temperature at which the phase transition of the two mesophase taken place is same, the temperature at which the phase transition has a slope increase is higher with deformed mesophase than quench-induced mesophase, and it indicates that the former one is much more stable. It is found that the regular conformation of 31 helices along stretching direction has a larger long-range order in deformed mesophase. That reason is used to explain why the deformed mesophase has a higher melt point.

Key words: synchrotron radiation WAXD, isotactic polypropylene, deformed mesophase, phase transition