聚对苯二甲酰对苯二胺草席晶形态的细微结构

本文采用溶剂腐蚀技术和电子显微镜法研究了聚对苯二甲酰对苯二胺(PPTA)草席晶形态的细微结构,发现了PPTA草席晶的真实形态结构系为沿剪切应力方向平行取向排列,并周期性地弯曲成锯齿状的微纤结构。其锯齿周期的大小平均约为1微米左右,正好与在偏光显微镜正交偏振片下所观察到的草席晶形态中一条晶带宽度的尺寸相当,因此可以认为在偏光显微镜下所看到的草席晶图像只不过是这种锯齿状微纤规则弯曲所形成周期性结构的一种光学效应而已。同时也直接观察到单个分离的微纤,它是由于液晶态溶液微区结构中取向的刚性链分子在剪切应力作用下产生滑移而形成的。

FINE STRUCTURE OF MAT-LIKE CRYSTALLINE MORPHOLOGY OF POLY (P-PHENYLENE TEREPHTHALAMIDE)

The fine structure of PPTA mat-like crystal has been studied by solvent etching technique and electron microscopy. It has been found that the mat-like crystal is made of zigzag fibrillar structure oriented along the shear direction in the film. The periodical length of the zigzag fibrils is about one micron, corresponding to the width of a band in mat-like crystal. Therefore, the morphology of mat-like crystal observed by polarizing microscopy is an optical effect resulted from the periodical structure of the zigzag fibrils. The structure of an isolated fibril has also been observed. It is made of consecutively linked plates which may be formed from the molecular slipping within the domain structure during the shear process. A new model is suggested to explain the structure of the PPTA film with mat-like crystalline morphology.