同步辐射原位研究构象有序对高分子结晶的影响

Spinodal-assisted crystallization is believed to be a promising physical mechanism of polymer crystallization. However, it has not been experimentally confirmed yet. Homogeneously nucleation allows more conformational chains formed without crystallization, which can be used to clarify the relationship between crystallization and conformation ordering. In this project, changes in corformational ordering and crystalline structure are monitored during homogeneous crystallization of isotactic polypropylene micro-droplets which are placed in the atactic polystyrene matrix using synchrotron radiation infrared microspectroscopy and X-ray microdiffraction. Through monitoring space distribution of corformational ordering, it is tested that if conformational ordering polymer chains aggregate prior to crystallization. This study will also investigate the influence of confornational ordering on crystallization behaviour after heating iPP mesophase at tempertures slightly above melting point in order to remain corformational ordering. Through this study, we aim to illustrate the relationship between corformational ordering and crystalline structure.This study takes full advantage of synchrotron radiation infrared microspectroscopy and X-ray microdiffraction,giving structural information during homogeneous crystallization, which cannot be obtained by other technologies used in the previou studies. This study could give an insight into polymer crystallization, and accumulate knowledge for preparing polymer materials with high properties through controlling pre-ordering structure.

旋节线相分离辅助结晶被认为是一种重要的高分子结晶机制，但一直未得到实验证实。均相成核可以使得高分子在低温下生成更多构象有序链段，从而有利于揭示构象有序与晶体有序的关系。本项目拟利用同步辐射显微红外和微聚焦X射线衍射研究置于无规聚苯乙烯基底的等规聚丙烯微球在均相成核过程中构象有序和晶体结构演化过程。通过观察构象有序在小球内空间分布，检测结晶前高分子熔体中是否存在构象有序在某些区域内的富集现象。同时研究聚丙烯中间相残留分子构象对结晶动力学的影响，揭示构象有序与晶体有序的相互关系。本研究能够给出高分子在均相成核过程中构象和晶体结构的演化，这是以前研究不能给出的，是近年来同步辐射显微技术和微聚焦的发展才有可能实现的。这项研究有可能加深人们对于高分子结晶前期的认识，并为调控预有序结构来制备性能更好的高分子材料积累经验。

高分子结晶一直是高分子研究的重点和难点。然而，由于其凝聚态结构的复杂性和多层次性，其机理一直没有得到阐明。在本项目中，我们从高分子特点（链构象和折叠链结构）出发，研究在高分子结晶过程中构象有序，晶体有序和取向有序之间的关系。利用傅里叶变换红外和同步辐射小角和宽角X射线散射，我们研究了纳米聚丙烯在升温过程相转变过程。实验发现，由左手和右手螺旋形成的双螺旋和链滑移是联系上述三个有序化过程的桥梁。另外，通过聚丙烯中间相和晶体记忆效应的研究发现，记忆熔体内存在折叠链结构是高分子记忆效应存在的必要条件。这个结构不存在晶体有序，但是存在取向有序和构象有序。取向有序使熔体保持低熵，有利于高分子成核。而构象结构的不同会对成核和生长产生不同的影响。本研究有利于深化人们对高分子结晶的认识。