高压结晶PET/PC共混体系中大尺寸聚合物伸直链晶体的形态观察

 大尺寸聚合物伸直链晶体在低维体系物理学的研究中具有不可替代的重要作用。但以往高压合成的聚合物伸直链晶体，尺寸较小且合成时间过长，使其作用至今未能显现。加入10%（质量分数）聚碳酸酯（PC）于聚对苯二甲酸乙二醇酯（PET）中，在研究PET/PC共混体系高压结晶行为的过程中快速合成了大量生长厚度超过100 μm 的聚合物伸直链晶体，并采用扫描电子显微镜对其进行了深入研究。研究表明，高压结晶PET/PC共混体系中存在不同类型的大尺寸伸直链晶体：完善的伸直链晶体、沿平行或垂直于C轴方向发生断裂的伸直链晶体、内聚能密度较大而发生内聚破裂的伸直链晶体、不同断裂方式下呈不同形态的楔形状伸直链晶体以及弯曲的伸直链晶体。同时对不同形态伸直链晶体的形成机理作了阐述。

SEM Observation of Large Polymer Extended-Chain Crystals in High-Pressure Crystallized PET/PC Blends

Large polymer extended-chain crystals have an important role that cannot be replaced in the study on low dimensional systems of physics. However, the small size of polymer extended-chain crystals that formerly had to be obtained through a long time confined their effect. Adding 10% (mass fraction) PC to PET, we obtained plenty of polymer extended-chain single crystals with C axis thickness exceeding 100 μm during the study on the high-pressure crystallization behaviors of PET/PC blends with a self-made piston-cylinder apparatus. For the first time, scanning electron microscope was employed to analyze them in a deep-going way. Large extended-chain crystals with various morphologies were observed by SEM, i. e. perfect extended-chain crystals, extended-chain crystals fractured along or perpendicular to C axis, extended-chain crystals with cohesive fracture surfaces, different wedge-shaped extended-chain crystals on different fracture surfaces and bending extended-chain crystals. Some mechanisms were also put forward for the formation of the observed large crystals.