Liu Xin, Wu Huanghu, Xu Wei, Jiang Yu, Zhang Junheng, Ye Bangjiao, Zhang Hongjun, Chen Sufang, Miao Menghe, Zhang Daohong
Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education & Hubei Key Laboratory of Catalysis and Materials Science, Hubei R&D Center of Hyperbranched Polymers Synthesis and Applications, South-Central Minzu University, Wuhan, 430074, China.
State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei, 230026, China.
Adv Mater. 2024 Mar;36(9):e2308434. doi: 10.1002/adma.202308434. Epub 2023 Dec 14.
The strength and toughness of thermoset epoxy resins are generally mutually exclusive, as are the high performance and rapid recyclability. Experimentally determined mechanical strength values are usually much lower than their theoretical values. The preparation of thermoset epoxy resins with high modulus, high toughness, ultrastrong strength, and highly efficient recyclability is still a challenge. Here, novel hyperbranched epoxy resins (Bn, n = 6, 12, 24) with imide structures by a thiol-ene click reaction. Bn shows an excellent comprehensive function in simultaneously improving the strength, modulus, toughness, low-temperature resistance, and degradability of diglycidyl ether of bisphenol-A (DGEBA). All the mechanical properties first increase and then decrease with minimization of the free volume properties. The improvement is attributable to uniform molecular holes or free volume by a molecular mixture of linear and hyperbranched topological structures. The precise measurement and controllability of the molecular free volume properties of epoxy resins is first discovered, as well as the imide structure degradation of crosslinked epoxy resins. The two conflicts are successfully resolved between strength and toughness and between high performance during service and high efficiency during degradation. These findings provide a route for designing ultrastrong, tough, and recyclable thermoset epoxy resins.
热固性环氧树脂的强度和韧性通常相互排斥，高性能和快速可回收性也是如此。实验测定的机械强度值通常远低于其理论值。制备具有高模量、高韧性、超强强度和高效可回收性的热固性环氧树脂仍然是一项挑战。在此，通过硫醇-烯点击反应制备了具有酰亚胺结构的新型超支化环氧树脂（Bn，n = 6、12、24）。Bn在同时提高双酚A二缩水甘油醚（DGEBA）的强度、模量、韧性、耐低温性和可降解性方面表现出优异的综合性能。所有机械性能均随着自由体积性能的最小化先增加后降低。这种改善归因于线性和超支化拓扑结构的分子混合物形成的均匀分子孔或自由体积。首次发现了环氧树脂分子自由体积性能的精确测量和可控性，以及交联环氧树脂的酰亚胺结构降解。成功解决了强度与韧性之间以及服役期间的高性能与降解期间的高效率之间的两个矛盾。这些发现为设计超强、坚韧且可回收的热固性环氧树脂提供了一条途径。
