同步辐射X射线方法原位研究聚丁烯-1拉伸诱导相转变

It is well known that stretching can greatly accelerate the phase transition of polybutene-1 from form II to form I and shorten the transition time, which typically requires a few weeks. However, the exact mechanism of this stretch-induced phase transition is not completely understood yet. In this project, the stretch-induced phase transition of polybutene-1 will be studied in detail using in situ synchrotron X-ray methods, together with various designed deformation protocols. We aim at elucidating the role of various deformation parameters, finding the dominant factor in inducing phase transition, quantifying the relationship of transition kinetics with stretch strength, and revealing the mechanism of stretch-induced phase transition. Moreover, by further utilizing ethylene-butene-1 copolymer and 1,5-hexadiene-butene-1 copolymer, we will explore the origin of intermediate amorphous phase in the indirect transition path at high temperature, and the influences of chain regularity and flexibility on the stretch-induced phase transition. This fundamental study on stretch-induced phase transition of polybutene-1 will rich theoretical knowledge, answer the controversial questions, and further direct control of property as well as development of new materials.

拉伸可以极大地加速聚丁烯-1 form II向form I的相转变，大幅缩短其在静态长达数周的转变时间。尽管这一效应已经被普遍接受，但其机理仍未清楚。本项目将利用同步辐射X射线方法和多种针对性的拉伸方案，对聚丁烯-1拉伸诱导相转变的临界条件和动力学进行系统研究。本项目将阐明不同拉伸外场参量对相转变的作用，明确主导相转变的拉伸因素，量化外场强度与相转变的关系，揭示相转变机理。我们还将结合乙烯-丁烯-1共聚物和1,5-己二烯-丁烯-1共聚物，探索高温相转变途径中无定形中间态的来源，以及链段规整性和柔顺性等分子性质对拉伸诱导相转变的影响。聚丁烯-1拉伸诱导相转变的机理研究不仅可以丰富理论知识，回答争议性基础问题，还可以直接指导性能调控和新材料开发。

聚1-丁烯是一类典型的多晶型聚合物，因其优异的物理机械性能引起了工业界和学术界的广泛关注。本项目聚焦聚1-丁烯的结构-性能关系，利用原位广角X射线衍射与拉伸测试结合方法，系统研究其拉伸诱导相转变行为。我们从相转变与外场参量的定量关系，拉伸诱导晶体取向，动态相含量与力学性能，以及分子结构对拉伸诱导相转变过程影响方面开展工作，旨在深入揭示拉伸诱导相转变机理，并建立微观相转变与宏观机械性能之间的定量关系。我们发现相转变过程与力学行为存在相互作用，拉伸诱导相转变的诱发需要力学屈服为前提，明确了相转变动力学的应力控制规律。晶型转变同时，片晶会依据拉伸温度、拉伸速率以及共聚单元浓度等条件，采用不同的取向方式。初始晶体中form I含量不改变相转变与屈服的对应关系，但会显著提高屈服应力，获得了相转变含量-应力的定量化转变曲线。基于分子结构与外力场的耦合作用，设计不同共聚单元类型和含量有效调控晶型转变，指导新型丁烯共聚物材料的开发与应用。