Dynamic Bottlebrush Polymer Networks: Self-Healing in Super-Soft Materials
Dynamic Bottlebrush Polymer Networks: Self-Healing in Super-Soft Materials
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DOI：
10.1021/jacs.0c01467
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发表时间：
2020-04-22
影响因子：
15
通讯作者：
Bates, Christopher M.
中科院分区：
文献类型：
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作者：
Self, Jeffrey L.;Sample, Caitlin S.;Bates, Christopher M.
我们介绍了一种使用瓶刷聚合物构建块来扩展共价自适应网络(CAN)中可获得的力学性能范围的设计策略。具有橡胶聚(4-甲基己内酯)侧链的明确定义的瓶刷聚合物在包括双内酯和强Lewis酸(己酸锡乙酯)的配方中进行了交联。所得材料在高温(160-180摄氏度)下表现出可调的应力松弛速率，这是由于动态的酯交联与残留的羟基进行了酯交换反应。改变交联剂装载量或瓶刷主干聚合度可产生约10-100 kpa的可预测低频剪切模数，远低于线性聚合物罐的典型值(1兆帕)。这些可伸展的网络在失效前可以拉伸到350%的应变，并经过有效的自我修复，在反复断裂和熔融处理后恢复其原始韧性的85%。总而言之，分子结构创造了新的机会，可以用其他方式难以实现的方式来定制罐头的机械性能。
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 cross-linked 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 degrees C) due to dynamic ester cross-links that undergo transesterification with residual hydroxy groups. Varying the cross-linker 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.