基于硼酸酯键交联的可回收酚醛树脂的结构设计和可控降解行为

The three-dimensional cross-linked structure of the traditional phenolic resins (PRs) formed during curing ensures them excellent performance and wide application, but also makes the efficient recovery or resource utilization of PR to be difficult problems. Therefore, it is an important way to realize effective curing, controlled degradation and efficient recovery of PR by constructing new cross-linked structure through dynamic covalent bond based on new chemical principles. This project focuses on the Ph-OH groups existed in the traditional PR. The chemical cross-linking among linear oligomer of thermoplastic phenolic resin (NR) was occurred by dynamic boronic ester bonds formed between Ph-OH and B-OH groups of arylboronic acid. By utilizing the alcoholysis characteristics of the curing resin in the mild conditions, the controlled degradation and efficient recovery take place. This project will synthesize a variety of prepolymers starting from the industrial NR to build a new resin system. Then the rules of the curing reactions for the resin system will be revealed. The formation and destruction laws of boronic ester structures will be clarified by using small-molecule model compounds as well. The relationship among the composition, structure and properties of the curing resins cross-linked by boronic ester bonds will be investigated. As a result, a new recyclable PR system with good mechanical properties and self-repair ability is obtained. Therefore, this project provides an environmentally friendly approach to efficiently recycle PR, and also opens up a new pathway for recycling other types of thermosetting resins.

在传统酚醛树脂(PR)中，固化后形成的三维交联结构在赋予其优良性能的同时，也使PR的高效回收或资源化利用成为一个难题。因此，运用新的化学原理构造基于动态共价键的新型交联结构，是实现PR的有效固化、可控降解和高效回收的重要途径。本项目注目于PR中固有的酚羟基，利用其与芳基硼酸发生反应形成硼酸酯键的性质，实现线形酚醛树脂齐聚物(NR)分子链之间的化学交联；利用硼酸酯键在温和条件下的醇解特性实现固化树脂的可控降解和高效回收。本项目将从工业化的NR出发，合成多种树脂预聚物，构建新型树脂体系，揭示树脂体系的固化反应规律；并借助模型化合物阐明硼酸酯结构的形成和破坏规律；掌握固化树脂及其复合材料的组成、结构和性能之间的关系，制备具有良好力学性能、可高效回收并具备一定自修复能力的新型树脂体系。因此，本项目提出了一条环境友好地实现PR高效回收的新途径，并可为开发其它类型的可回收热固性树脂提供了一个新思路。

在传统酚醛树脂(PR)中，固化后形成的三维交联结构在赋予其优良性能的同时，也使PR的高效回收或资源化利用成为一个难题。因此，本研究运用新的化学原理构造基于动态共价键的新型交联结构，以实现PR的有效固化、可控降解和高效回收。本项目从工业化的NR出发，利用PR中固有的酚羟基与芳基硼酸发生反应形成硼酸酯键的性质，实现了线形酚醛树脂齐聚物(NR)分子链之间的化学交联；通过调控芳基硼酸的种类和数量以及NR的种类和分子量，明确了硼酸酯的种类和比例对固化树脂的结构和性能的影响规律，揭示了树脂体系的固化反应规律。利用硼酸酯键在温和条件下的醇解特性实现了固化树脂及其复合材料的可控降解和高效回收，而且经过多次回收再利用后，回收纤维的结构、表面形貌和性能基本与回收前相当。基于不同的硼酸酯键交联的NR固化树脂，系统地研究了硼酸酯结构的形成和破坏所引起的固化树脂的结构和性能的变化规律，揭示了材料的微观结构与宏观性能之间的关系，并获得了具有良好力学性能、可高效回收和具备一定自修复能力的PR以及复合材料。因此，本项目提出了一条环境友好地实现PR高效回收的新途径，并可为开发其它类型的可回收热固性树脂提供了一个新思路。