Orientation-Induced Crystallization in Polymers

该研究旨在探索聚合物取向诱导结晶的几个基本问题。 这些问题包括：（1）取向链中结晶初始阶段的机理，（2）从含有不同取向度的链的体系中结晶的总体动力学，（3）分子量、分子量分布、链结构和链支化对取向诱导结晶的影响，（4）分子分散的纳米结构分子对链取向的影响，（5）由取向晶相、取向介晶相和无取向非晶相组成的形貌。 为实现这些目标，建议开展四个研究项目，包括：（a）在阶跃剪切和稳态剪切条件下的弱剪切流动研究，（B）强拉伸流动研究，（c）聚合物中分子分散的纳米结构分子的作用研究，以及（d）使用超临界二氧化碳（CO2）作为控制分子取向的手段来研究取向聚合物中的结晶。 计划的实验将包括使用流变学、高压装置、原位光学（光散射、双折射和拉曼光谱）和X射线（同步辐射的小角和广角X射线散射）技术以及非原位显微镜技术的综合方法。研究的意义在于取向诱导结晶仍然是当今聚合物加工中最重要的问题之一，并且该主题尚未完全理解。 希望通过拟议的研究，可以获得对该主题的深入了解，提高将结晶聚合物的结构，形态，工艺和性能关系联系起来的能力，从而使聚合物工业受益。

The proposed research aims to explore several fundamental issues of orientation-induced crystallization in polymers. These issues include: (1) the mechanism of initial stages of crystallization in oriented chains, (2) the overall kinetics of crystallization from the system containing chains of varying degrees of orientation, (3) the effects of molecular weight, molecular weight distribution, chain architecture and chain branching on orientation-induced crystallization, (4) the influence of molecularly dispersed nanostructured molecules on the chain orientation, and (5) the resultant morphology consisting of oriented crystal, oriented mesomorphic and unoriented amorphous phases. To accomplish these goals, it is proposed to carry out four research projects including: (a) the weak shear-flow study under step-shear and steady-state shear conditions, (b) the strong elongation-flow study, (c) the study of the effect of molecularly dispersed nanostructured molecules in polymers, and (d) the study of crystallization in oriented polymers using supercritical carbon dioxide (CO2) as a mean to control molecular orientation. The planned experiments will include the use of combined methods of rheology, a high-pressure apparatus, in-situ optical (light scattering, birefringence and Raman spectroscopy) and x-ray (small- and wide-angle x-ray scattering with synchrotron radiation) techniques and ex-situ microscopic techniques.%%%The significance of the research lays in the fact that orientation-induced crystallization remains one of the most important problems in polymer processing today, and the subject is not fully understood. It is hoped that with the proposed study, an in-depth understanding about the subject can be obtained, increasing the ability to correlate the structure, morphology, process and property relationships for crystalline polymers, thus benefiting the polymer industry.