单双轴拉伸条件下高分子形成半结晶结构的分子模拟研究

Polymer semi-crystalline structure is a fundamental problem of polymer physical chemistry, but it also contains an important meaning to the processing of polymer materials. Molecular simulation has become an important approach in this field. In the past, the molecular simulation study on the formation mechanism of polymer semi-crystalline structure is mainly under the quiescent conditions, while common industrial processing of semi-crystalline polymers require a dynamic stretching process of solidification, such as plastic molding, fiber spinning, film stretching, film blowing, and plastic foaming. On the basis of the achievements in our previous investigations, we plan to use dynamic Monte Carlo simulations in combination with the multi-scale simulation approaches like Molecular Dynamics simulations, and to set up several simulation platforms in mimicking the uniaxial and biaxial (sequential and simultaneous) stretching processing. Using these platforms, we will systematically investigate the key problems of strain-induced polymer crystallization and semi-crystalline structure reorganization. We will understand the factors of stresses and strains, temperatures and their gradients, molecular weights and their distributions, comonomers and blending polymers. The target of this project is to grasp the fundamental rules of strain-induced polymer crystallization and structure reorganization in several common and practical processing, to refine new concepts and to develop new theories. The theoretical results will guide the practical processing of polymeric materials, and contribute to the foundation for our polymer industry to develop from traditional to intelligent manufacturing.

高分子半结晶结构是高分子物理化学的重要基础研究内容，也在高分子材料加工领域具有特别重要的意义。分子模拟已经成为其微观形成机理的重要研究手段，但相关的基础研究过去主要集中在静态条件下，而非面向实际高分子材料加工固化过程的动态拉伸条件，例如注塑、纺丝、拉膜、吹膜和发泡等。我们在前期研究拉伸诱导高分子结晶成核所取得的进展基础上，拟进一步采用动态蒙特卡洛分子模拟结合跨尺度的分子动力学模拟，建立模仿单轴和双轴（分同时和先后）拉伸结晶过程的分子模拟研究平台，系统地研究高分子拉伸诱导结晶和半结晶结构重组的关键科学问题，阐明拉伸应力场、温度场、分子量及其分布、共聚或共混等调控因素对高分子形成半结晶结构微观机理的影响，目标是掌握高分子拉伸诱导结晶和半结晶结构重组在几种常见加工工艺中的基本规律，提炼新概念，发展新理论，以期将理论成果应用于指导高分子加工实践，为我国传统高分子加工业向智能制造化方向发展奠定基础。

本项目系统地研究了高分子应变诱导结晶过程从熔体初态、结晶机理到结晶形貌的微观机制，在取向高分子应力松弛的分子间协同作用机制、应变诱导高分子结晶的形态演化机制和热塑性弹性体应变诱导结晶的分子建模及其形态调控机制这三个主要方面取得了原始创新性的研究结果，共发表基金标注学术论文24篇（其中第一标注论文16篇，第二标注论文8篇），合作申请专利并获批1项，组织学术交流活动8次，应邀作国际学术会议分会报告11次，指导博士后2名，培养博士生19名（其中已毕业6名），培养硕士生18名（其中已毕业11名），项目负责人获2020年美国物理学会会士荣誉称号。项目研究进展在执行团队与埃克森美孚公司亚太研发中心和瑞声科技（南京）有限公司的合作研究项目中获得应用推广。项目直接经费到账300万，截止到2022年12月底结余65.0560万元，经费使用合理，研究工作达到预期的计划要求，整体完成了预定的研究目标。