We introduce a design strategy to expand the range of accessible mechanical properties in covalent adaptable networks (CANs) using bottlebrush polymer building blocks. Well-defined bottlebrush polymers with rubbery poly(4-methylcaprolactone) side-chains were crosslinked in formulations that include a bislactone and strong Lewis acid (tin ethylhexanoate). The resulting materials exhibit tunable stress relaxation rates at elevated temperatures (160-180 °C) due to dynamic ester crosslinks that undergo transesterification with residual hydroxy groups. Varying the crosslinker loading or bottlebrush backbone degree of polymerization yields predictable low-frequency shear moduli ca. 10-100 kPa, well below values typical of linear polymer CANs (1 MPa). These extensible networks can be stretched to strains as large as 350% before failure and undergo efficient self-healing to recover >85% of their original toughness upon repeated fracture and melt processing. In summary, molecular architecture creates new opportunities to tailor the mechanical properties of CANs in ways that are otherwise difficult to achieve.

中文翻译：

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动态瓶刷聚合物网络：超软材料中的自修复

我们引入了一种设计策略，以使用瓶刷聚合物构建块扩展共价适应性网络 (CAN) 中可访问的机械性能范围。具有橡胶状聚（4-甲基己内酯）侧链的明确定义的瓶刷聚合物在包含双内酯和强路易斯酸（乙基己酸锡）的配方中交联。由于动态酯交联与残留羟基发生酯交换反应，所得材料在高温（160-180°C）下表现出可调的应力松弛率。改变交联剂负载量或瓶刷主链聚合度会产生可预测的低频剪切模量。10-100 kPa，远低于线性聚合物 CAN 的典型值 (1 MPa)。这些可延展的网络在失效前可以拉伸至高达 350% 的应变，并进行有效的自我修复，在反复断裂和熔融加工时恢复 85% 以上的原始韧性。总之，分子结构创造了以其他方式难以实现的方式定制 CAN 机械性能的新机会。