Due to the exchangeability of dynamic covalent bonds in the covalent adaptable networks (CANs) at elevated temperature, they possess recyclability while still maintaining many of the superior properties of thermosets. The exploration of dynamic covalent chemistry is of great significance to the expansion of CANs library and hence the sustainable development of thermosets. In this work, we discovered that, in absence of catalyst, the direct metathesis of the cyclic acetals proceeds while the acyclic acetals cannot. The metathesis kinetics of the cyclic acetals were fully revealed with model compounds. For the CANs demonstration, a series of cross-linked spirocyclic acetal polymers with excellent reprocessability, high thermal stability, and high refractivity were prepared via thiol–ene click polymerization. We envisage that the uncovering of the catalyst-free metathesis of cyclic acetals will enrich the dynamic chemistry of acetals and greatly promote the development of acetal-based CANs and their potential applications in optical devices.

中文翻译：

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环缩醛和螺环缩醛共价适应性网络的无催化剂复分解

由于在高温下共价适应性网络 (CAN) 中动态共价键的可交换性，它们具有可回收性，同时仍保持热固性材料的许多优越性能。动态共价化学的探索对于CANs库的扩展和热固性材料的可持续发展具有重要意义。在这项工作中，我们发现，在没有催化剂的情况下，环状缩醛的直接复分解进行，而无环缩醛则不能。模型化合物充分揭示了环状缩醛的复分解动力学。对于 CAN 演示，通过硫醇-烯点击聚合制备了一系列交联的螺环缩醛聚合物，这些聚合物具有优异的可再加工性、高热稳定性和高折射率。