Developing high-performance polymers in a sustainable and simple manner while efficiently converting renewable resources is extremely challenging. In this study, three different diamine (aliphatic, cyclic, and aromatic) derived curing agents with dynamic imine covalent bond were successfully synthesized using vanillin and their chemical structures were validated by FTIR, GCMS and NMR spectroscopy. Further, curing behavior, mechanical and thermal properties of the resulting epoxy thermosets were investigated by DSC, tensile analysis, TGA, and DMA. The curing response of aliphatic amine-derived epoxy polymer shows significantly higher but lower flexural strength (∼37 %), flexural modulus (∼53 %), T_g (∼52 %), storage modulus (∼8 %), T_d5 % (∼4.5 %), and Char₇₀₀ (∼54 %) properties due to the steric-hindrance of aromatic and cyclic rings in the molecular structures. Moreover, these epoxy thermosets can be reprocessed, and repaired several times without losing their mechanical and thermal properties due to incorporate dynamic imine bond into their molecular structures. Notably, the pendant backbone-chain in curing agents significantly influences the dynamic manners of the cured thermosets and aliphatic-chain exhibits the quickest stress relaxation performance. Finally, all cured products showed excellent chemical stability in various solvents. These remarkable findings offer important clues for comprehending the structure-property link of recyclable epoxy thermosets with different amine-derivatives.

中文翻译：

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研究胺基可回收香兰素环氧热固性塑料的结构-性能相关性


以可持续和简单的方式开发高性能聚合物，同时高效转换可再生资源极具挑战性。在本研究中，使用香兰素成功合成了三种不同的二胺（脂肪族、环状和芳香族）衍生的具有动态亚胺共价键的固化剂，并通过 FTIR、GCMS 和 NMR 光谱验证了它们的化学结构。此外，通过 DSC、拉伸分析、TGA 和 DMA 研究了所得环氧树脂热固性材料的固化行为、机械和热性能。脂肪胺衍生环氧树脂聚合物的固化响应表现出明显较高但较低的弯曲强度 （∼37 %）、弯曲模量 （∼53 %）、T_g （∼52 %）、储能模量 （∼8 %）、T_{d5 %} （∼4.5 %） 和 Char₇₀₀ （∼54 %） 性能，这是由于分子结构中芳香族和环状环的空间位阻造成的。此外，这些环氧树脂热固性材料可以进行多次再加工和修复，而不会因将动态亚胺键掺入其分子结构而失去其机械和热性能。值得注意的是，固化剂中的悬垂主链会显著影响固化热固性塑料的动力学方式，并且脂肪族链表现出最快的应力松弛性能。最后，所有固化产物在各种溶剂中均表现出优异的化学稳定性。这些显著的发现为理解具有不同胺衍生物的可回收环氧树脂热固性材料的结构-性能联系提供了重要线索。