基于力响应膨胀单体的低收缩环氧树脂的合成与性能研究

Epoxy resin (EP) is widely used in the national defense industry due to its excellent properties. However, the shrinkage during curing, which causes internal stress and mechanical property decline, becomes an urgent problem in the weapon system. Here we would design and synthesize a novel kind of mechanoresponsive expansion monomer for EP modification. Double ring opening reaction of expansion monomer could be initiated by the destructive internal stress during curing process of EP, so as to solve the volume shrinkage problem. When cured, the expansion monomer would be covalently linked to the crosslinked network of EP, and the internal stress induced by volume shrinkage would initiate the ring opening reaction of the expansion monomer under appropriate conditions, dissipating the internal stress and reducing the volume shrinkage simultaneously. The evolution and distribution of internal stress could be shown from macro scale by monitoring the ring opening reaction through confocal laser scanning microscopy and UV spectrum; the effect of monomer’s structure on the curing shrinkage and property of epoxy resin would be studied systematically through experiment and DFT calculation, thus providing basis for structure optimism. This project is expected to develop novel kind of stimulus responsive expansion monomers and provide a new way to reduce the internal stress of thermosetting polymers.

环氧树脂因性能优异广泛应用于国防工业，但固化时的体积收缩及由此产生的内应力会显著降低材料的性能与稳定性，成为武器系统中急需解决的问题。本项目拟设计并合成一类力响应膨胀单体，探索利用破坏性的固化内应力诱导膨胀单体发生双开环反应的新方法，用于解决环氧树脂的固化收缩问题。固化时膨胀单体共价接入环氧树脂交联网络，体积收缩产生的内应力诱导膨胀单体发生开环反应，耗散内应力并减小体积收缩。通过共聚焦显微镜、紫外光谱等研究膨胀单体在环氧树脂固化内应力下的响应行为，可从宏观尺度反映材料内应力的分布情况及内应力随体积收缩的演变过程；通过实验结合理论计算研究膨胀单体的结构对环氧树脂固化收缩及性能的影响规律，可为膨胀单体的结构优化提供思路。本项目有望开发具有力响应性的新型膨胀单体并用于制备低收缩环氧树脂，也将为降低热固性聚合物内应力提供新思路。

本项目围绕热固性环氧聚合物的收缩问题，开展了低收缩环氧聚合物的设计与性能研究，通过开展新型力热响应的化合物作为膨胀单体，以降低环氧聚合物的热膨胀系数，弥补高热膨胀系数带来的体积收缩以降低材料应力，相关研究结果均具有较大的创新与突破。一方面，通过采用负热膨胀无机填料LaFe10.5Co1.0Si1.5制备了低膨胀环氧复合材料（27×10-6/K，228-323K），并通过磁场诱导填料的梯度分布构建了低膨胀环氧梯度功能材料；另一方面，聚焦于热致收缩结构二苯并环辛二烯（DBCOD），合成负热膨胀的线性聚酰胺NPA共混改性环氧树脂，或者通过在DBCOD结构上引入氨基、羧基等功能取代基与环氧树脂共聚两条技术途径，实现热固性环氧材料的热膨胀性能调控，证明DBCOD的可逆构象转变过程在三维交联网络中仍能够发生，但交联网络刚性与玻璃化转变温度的增加不利于构象转变过程的发生与热膨胀性能调控。通过上述研究获得了多种在宽温度区间内具有负热膨胀（-32.4 ×10-6/K，50-100℃）乃至零热膨胀性能（0.51 ×10-6/K，80-120℃）的热固性环氧聚合物。此外，建立了基于罗丹明力敏基团的力响应环氧聚合物的合成方法，获得了同时具备力致变色/荧光响应与负膨胀性能的环氧材料。