Recycling of polyurethanes is largely infeasible due to the harsh reprocessing conditions and associated risks of side reactions and degradation whereas polymer networks incorporating dynamic covalent bonds represent an attractive approach to the design of recyclable materials. Here, we report findings on the dynamic nature of thiourethanes, and their application as a new class of recyclable analogs of urethane materials. A series of small molecule experiments was initially conducted to determine the equilibrium constant and exchange reaction kinetic constant for the thiol–isocyanate reaction. Furthermore, incorporating those thiourethane moieties into a cross-linked network resulted in thermoset materials that are readily depolymerized to liquid oligomers. The resultant oligomers can be re-crosslinked to thiourethanes without any loss of performance nor change in mechanical properties (peak stress of 25 MPa with max strain of 200%). Moreover, the recycled thiol oligomers from thiourethane network polymers could potentially be transformed into other materials with mechanical properties that exceed those of the initial, pristine thiourethane materials. Overall, the ease with which these polythiourethanes are polymerized, recycled and reformulated gives a new direction and hope in the design of sustainable polymers.

中文翻译：

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通过动态硫代氨基甲酸酯键实现聚（硫代氨基甲酸酯）热固性材料的化学回收

由于苛刻的后处理条件以及伴随的副反应和降解风险，聚氨酯的回收在很大程度上是不可行的，而结合了动态共价键的聚合物网络则是设计可回收材料的一种有吸引力的方法。在这里，我们报告有关硫代氨基甲酸酯的动态性质及其作为一类新的可重复使用的氨基甲酸酯材料类似物的应用的发现。最初进行了一系列小分子实验，以确定硫醇-异氰酸酯反应的平衡常数和交换反应动力学常数。此外，将那些硫代氨基甲酸酯部分并入交联网络中导致热固性材料易于解聚为液体低聚物。所得的低聚物可以与硫代氨基甲酸酯再交联，而不会降低性能或改变机械性能（峰值应力为25 MPa，最大应变为200％）。而且，从硫代氨基甲酸酯网络聚合物回收的硫醇低聚物可能被转化成机械性能超过原始的原始硫代氨基甲酸酯材料的其他材料。总体而言，这些聚硫代氨基甲酸酯的聚合，再循环和重新配制的简便性为可持续聚合物的设计提供了新的方向和希望。原始的硫代氨基甲酸酯材料。总体而言，这些聚硫代氨基甲酸酯的聚合，再循环和重新配制的简便性为可持续聚合物的设计提供了新的方向和希望。原始的硫代氨基甲酸酯材料。总体而言，这些聚硫代氨基甲酸酯的聚合，再循环和重新配制的简便性为可持续聚合物的设计提供了新的方向和希望。