Ordering Process of Polymers during the Induction Period of Crystallization Observed by the Simultaneous Thermal Analysis and Molecular Vibration Spectroscopy

采用同步差示扫描量热仪和傅里叶变换红外光谱（DSC-FTIR）研究了聚合物的结晶机理，特别是结晶诱导期的有序过程。DSC-FTIR和DSC- xrd研究了聚偏氟乙烯（PVDF）、辛二聚聚苯乙烯（sPS）、聚对苯二甲酸乙酯（PET）和正构烷烃的相变行为。熔融态PVDF结晶的构象顺序先由随机到恍惚-间扭式，再由α-型进行位置排序。在结晶诱导期，sPS和PET的构象顺序相似。采用DSC-XRD和DSC-FTIR对PET从玻璃态和熔融态的结晶过程进行了观察。从构象和结构的角度探讨了结晶过程的分子机理。由于π-电子相互作用，芳环的堆积导致了成核过程。芳香部分和乙烯部分分别进行构象排序和位置排序对结晶焓有影响。预熔结晶和二次结晶过程是由芳香族部分和乙烯部分的构象次序失调的补偿而发生的。

The crystallization mechanism of polymers, especially the ordering process during the induction period of crystallization was investigated by the simultaneous differential scanning calorimeter and Fourie transform infrared spectroscopy (DSC-FTIR). The time resolutions of DSC and FTIR were 1 sec. Phase transition behavior of poly(vinylidene fluoride) (PVDF), syndiotactic polystyrene (sPS), poly(ethylene terephthalate) (PET) and n-alkanes were investigated by DSC-FTIR and DSC-XRD.The conformational ordering from random to trance-gauche proceeded before the positional ordering of α-form for the crystallization of PVDF from the molten state. Similar conformational ordering was observed for sPS and PET during the induction period of crystallization.The crystallization process of PET from the glassy state and the molten state were observed by DSC-XRD and DSC-FTIR. Molecular mechanism of crystallization process was discussed from conformational and structural viewpoint. The stacking of aromatic rings due to π-electron interaction caused the nucleation process. Conformational ordering of aromatic part and ethylene part proceeding individually and positional ordering contributed to crystallization enthalpy. The pre-melt crystallization and secondary crystallization process were occurred by the compensation of dis-orders between conformational ordering of aromatic part and ethylene part.