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The introduction of concept of the three domains of isotactic polypropylene (iPP) by Wittmann and Lotz et al. is an important advance in understanding the influence of the melt structures on the crystallization behaviors and consequent properties. To further understand the physical nature of the melt structures, the crystalline structures of iPP after thermal treatment in the three domains are systematically investigated. It is found that after treated at different domains the crystal morphologies, including the sizes and birefringence of spherulitic, the proportion of radial and tangential lamellae, etc., have distinctly different features. Our study reveals that the “nuclei” at domain II compose of locally ordered chains and the induced memory effect could not be erased under annealing treatment, while the “nuclei” at domain III compose of crystal fragments, which will aggregate under annealing process. Based on our results, highly schematic diagrams are proposed to illustrate the probable physical characteristics of the melt structures at the three different domains. 相似文献
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螺双芴在电致发光材料领域的应用 总被引:1,自引:0,他引:1
螺双芴分子具有非平面的空间结构,两个芴单体以sp^3杂化的C原子为中心桥联在一起。将其引入到具有电致发光特性的分子中,对于提高分子的热稳定性和光谱稳定性等方面具有很大的应用价值。本文主要介绍了近年来螺双芴结构在有机/聚合物电致发光材料的分子设计上的研究进展,并对研究前景作了简要的展望。 相似文献
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硬脂酸镧复合物对聚丙烯β晶型的诱导作用 总被引:23,自引:0,他引:23
F等规聚丙烯(iPP)的分子链均为3螺旋构型,可形成α,β,γ,δ和拟六方态等5种晶体结构,β晶型(六方)的PP具有良好的韧性^[1,2],近年来因在增韧及制造电容器粗化膜方面有独特性能而受到重视,但β晶型在热力学上是准稳定,动力上是不利于生成的一种晶型[3],只有利用特殊方式才能获得,如选取合适的熔融、结晶温度及一定的温度梯度^[4],剪切取向^[5],使用成核剂[3,6~12]等,前两种方法不易实施,添加能诱导生成β晶型的特效成核剂是目前获得较高含量β晶型PP的可行途径,目前已知的β成核剂主要有两类,一类是少数具有准平面结构的稠环化合物,如γ晶型喹吖啶酮红染料E3B^[6]和三苯二噻^[7]等,另一类是元素周期表中少数第IIa 族金属的某些盐类及其二元羧酸的复合物,典型的例子如钙的亚氨酸盐^[8],硬脂酸钙/癸脂酸钙/癸二酸体系等^[3,9,12]. 相似文献