Conventional polymer networks are incapable of being reprocessed or recycled in the melt state, leading to sustainability and economic losses associated with spent polymer networks. With the incorporation of hydroxyurethane dynamic cross-links resulting from reaction of tricyclocarbonate and telechelic amine-terminated polymer, polybutadiene (PB) networks and poly(tetramethylene oxide) (PTMO) networks are reprocessable with full property recovery after multiple molding steps. Two types of small-molecule chain extender are incorporated into these networks to tune their morphologies, cross-link densities and associated properties. Addition of m-xylylenediamine (XYL) chain extender to PTMO networks increases the hard-segment content and leads to nanophase separation, which is absent when XYL is not present, and the elimination of cold crystallization behavior that is observed in PTMO networks without XYL. Addition of XYL also increases the cross-link density and rubbery plateau modulus of both PB and PTMO networks, and the resulting materials remain fully reprocessable. In contrast, addition of divinylbenzene dicyclocarbonate (DVBDC) chain extender enhances the cold crystallization behavior of molded PTMO-based networks and their crystallinity. Addition of DVBDC reduces the cross-link density and rubbery plateau modulus of both PB and PTMO networks, and the resulting networks exhibit selective property losses after reprocessing. This study demonstrates the simple and effective use of chain extenders in achieving tunability of dynamic network properties to satisfy requirements in different potential applications. It also provides a better understanding of structure-property relationships in dynamic covalent networks from both chemical and physical standpoints.

常规的聚合物网络不能在熔融状态下进行再加工或再循环，从而导致与废聚合物网络相关的可持续性和经济损失。通过引入羟基氨基甲酸酯，其是由三环碳酸酯和远螯胺终止的聚合物反应而产生的动态交联，可在多个模塑步骤后对聚丁二烯（PB）网络和聚四氢呋喃（PTMO）网络进行再加工，并恢复其全部性能。这些网络中结合了两种类型的小分子扩链剂，以调节其形态，交联密度和相关性能。m的加法-PTMO网络中的-xylylenediamine（XYL）扩链剂增加了硬段含量，并导致纳米相分离（当不存在XYL时则不存在），并且消除了在没有XYL的PTMO网络中观察到的冷结晶行为。XYL的添加还增加了PB和PTMO网络的交联密度和橡胶平台弹性模量，并且所得材料保持完全可再加工。相反，添加二乙烯基苯二环碳酸酯（DVBDC）扩链剂可增强基于PTMO的模塑网络的冷结晶行为及其结晶度。DVBDC的添加降低了PB和PTMO网络的交联密度和橡胶态平稳模量，并且所得的网络在再加工后表现出选择性的性能损失。这项研究证明了扩链剂在实现动态网络特性的可调性方面的简单有效的使用，以满足不同潜在应用中的需求。从化学和物理的角度，它也提供了对动态共价网络中结构-性质关系的更好理解。