具有优异性能的动态共价聚氨酯网络以及回收后的交联密度和单体回收潜力,ACS Applied Energy Materials

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具有优异性能的动态共价聚氨酯网络以及回收后的交联密度和单体回收潜力
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2020-04-14 00:00:00 , DOI: 10.1021/acsapm.0c00378
Xi Chen ₁ , Sumeng Hu ₁ , Lingqiao Li ₁ , John M. Torkelson _{1,

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Affiliation

涉及缔合和解离机理的动态氨基甲酸酯化学可用于实现交联聚氨酯（PU）网络中的可再加工性。我们发现，通过掺入过量的游离羟基可以增强动态共价PU网络的性能恢复和热稳定性，从而在羟基和异氰酸酯基的化学计量不平衡的情况下进行聚合反应，并将交联剂官能度从三个增加到四个。游离羟基可抑制氨基甲酸酯键的回复并在后处理条件下将与释放的异氰酸酯基团相关的副反应减至最小，而四官能交联剂则可在少量副反应的情况下保持网络完整性。利用这些策略，我们开发了一个PU网络，在实验误差范围内，经过多个再加工步骤后，交联密度和拉伸性能恢复了100％，这之前从未有过报道。我们还证明了在相对温和的条件下通过醇解从PU网络中回收单体的潜力。我们的研究不仅为解决PU网络回收这一长期存在的问题提供了解决方案，而且还提供了改善可重处理网络的属性恢复的简单策略。

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Dynamic Covalent Polyurethane Networks with Excellent Property and Cross-Link Density Recovery after Recycling and Potential for Monomer Recovery

Dynamic urethane chemistry, which involves both associative and dissociative mechanisms, can be used to achieve reprocessability in cross-linked polyurethane (PU) networks. We discovered that property recovery and thermal stability of dynamic covalent PU networks can be enhanced by incorporating excess free hydroxyl groups, thus performing polymerization reactions at slight stoichiometric imbalance of hydroxyl and isocyanate groups, and by increasing the cross-linker functionality from three to four. While free hydroxyl groups suppress the reversion of urethane links and minimize side reactions associated with liberated isocyanate groups under reprocessing conditions, tetrafunctional cross-linkers help to maintain network integrity in the presence of small levels of side reactions. Using these strategies, we developed a PU network that, within experimental error, exhibits 100% recovery of cross-link density and tensile properties after multiple reprocessing steps, which has not been reported before. We also demonstrated the potential of recovering monomer from PU networks by alcoholysis under relatively mild conditions. Our study not only offers a solution to the long-standing issue of PU network recycling but also provides simple strategies to improve property recovery of reprocessable networks.

更新日期：2020-04-14

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