面向通用材料的动态共价交联热固性树脂设计合成及其独特结晶、流变与自修复特性研究

Thermosets are widely used in electronic and aerospace fields due to their excellent mechanical and thermal properties. But due to the irreversibility of traditional covalent bonds, thermosets were difficult to recycle, and thus causing serious environmental problems. In recent years, with the introduction of reversible dynamic covalent bonding into thermoset resin system, thus the traditional thermoset possess interesting malleable and self-healing properties were obtained. This project will go further in to this novel dynamically cross-linked malleable thermoset through the molecular design and network design of -O-CH2-O-, -N-CH2-O-, -N-CH2-N- and -N-CH2-S- dynamic acetal bonding, -CH=N- dynamic Schiff-base bonding and -S-S- dynamic polysulfide bonding. We will thoroughly study the complicated chemical and physical process during thermal processing, and gain insight in to the relationship between the material design of dynamic covalent bonding and their thermal mechanical properties, rheological properties, malleability, weldability and liquid fragility etc. Finally we will establish a model to describe the relation between the network structure of dynamic malleable thermoset resins and their rheology and thermal mechanical properties under the stress field and the thermal fields. We hope through this project, we can lay a solid foundation for the design and synthesis of new dynamic thermosetting resin based on dynamic covalent bonding with unique malleable property, self-healing property and silica-like rheological properties.

热固性树脂以其优异的热机械性能获得了广泛的应用，但是由于传统共价键的不可逆性，热固性树脂在使用后难以回收再利用，从而造成巨大的环境问题。随着动态共价化学的深入，将具有可逆特性的动态共价键引入热固性树脂，赋予其一定程度的可加工性与可修复性。本项目将进一步深入这类新型的动态共价键连接的聚合物网络材料，重点面向通用热固性树脂体系，通过精细的动态缩醛键设计、动态甲亚胺键设计以及动态多硫键设计，深入而系统的研究动态共价键引入通用聚合物材料体系所需要解决的分子设计、材料设计与复合材料制备等难题，详细研究动态共价键的引入及其动力学调控对聚合物树脂体系及其纤维增强复合材料的热机械性能、结晶性能、流变性能以及可加工性、可修复性与液体脆性等的影响规律。建立描述这类新型热固性树脂网络结构演变与力场和热场之间关系的模型。为开发具有通用用途的新型动态共价交联热固性树脂及其纤维增强复合材料打下坚实的基础。

本项目以动态共价化学为基础，特别是利用O、N、S等在通用聚合物中常见的元素进行动态共价网络设计，开展面向通用聚合物材料的新型动态交联热固性树脂的合成、制备与结构-性能关系研究。具体来讲，通过精细的-O-CH2-O-、-N-CH2-O-和-N-CH2-S-等动态缩醛键设计，制备一系列基于聚苯并噁嗪与聚苯并噻嗪结构的Vitrimer材料体系。以价廉而易于获得的单质硫作为单体，利用-S-Sn-S-动态多硫键设计，制备了一系列具有光热双塑化特性的聚硫网络。特别是利用插烯脲结构Vitrimer网络，获得具有优异力学性能与低温加工性能的Vitrimer材料。本项目详细研究了缩醛、多硫键以及插烯脲等动态共价键的引入及其动力学调控对聚合物网络的热机械性能、结晶动力学、流变性能以及可加工性与可修复性等的影响规律。特别是将结晶性引入Vitrimer体系，通过拓扑受限调控动态共价键的动力学特性，为解决Vitrimer材料的加工性与稳定性矛盾提供了全新的策略。项目的研究成果为开发易于大规模工业制备且具有可加工性、可修复性与可回收性的新型Vitrimer聚合物网络材料奠定了较好的基础。