The Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China.
School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, Singapore 21 Nanyang Link, Singapore, 637371, Singapore.
Macromol Rapid Commun. 2023 Aug;44(15):e2300133. doi: 10.1002/marc.202300133. Epub 2023 Jun 1.
The development of catalyst-free ester-based covalent adaptable networks (CANs) provides a new approach to achieve milder reaction conditions to reprocess thermoset resins. Despite recent advances, however, accelerating network rearrangements requires the introduction of hydroxyl groups into the network. In this study, disulfide bonds are introduced into the CANs to add new kinetically facile pathways to accelerate network rearrangement. Kinetic experiments using small molecule models of the CANs show that the presence of the disulfide bonds can accelerate transesterification. These insights are applied to synthesize new kinds of poly(β-hydrazide disulfide esters) (PSHEs) using thioctic acyl hydrazine (TAH) as a precursor for ring-opening polymerization with the hydroxyl-free multifunctional acrylates. The PSHE CANs have lower relaxation times (505-652 s) than the polymer containing only β-hydrazide esters (2903 s). The ring-opening polymerization of TAH improves the crosslinking density, heating resistance deformation temperature, and UV shielding performance of the PSHEs. Thus, this work provides a practical strategy to reduce the reprocessing temperatures of CANs.
无催化剂的基于酯的共价适应性网络（CANs）的发展为实现更温和的反应条件来再加工热固性树脂提供了一种新方法。然而，尽管最近取得了进展，但加速网络重排仍需要在网络中引入羟基。在这项研究中，二硫键被引入 CANs 中，以增加新的动力学上易于接近的途径来加速网络重排。使用 CANs 的小分子模型进行的动力学实验表明，二硫键的存在可以加速酯交换反应。这些见解被应用于使用硫辛酸酰肼（TAH）作为无羟基多功能丙烯酸酯开环聚合的前体来合成新型聚（β-腙二硫代酯）（PSHEs）。PSHE CANs 的弛豫时间（505-652 s）低于仅含有β-腙酯的聚合物（2903 s）。TAH 的开环聚合提高了 PSHEs 的交联密度、耐热变形温度和 UV 屏蔽性能。因此，这项工作提供了一种实用的策略来降低 CANs 的再加工温度。
