Molecular understanding for large deformations of soft bottlebrush polymer networks
Molecular understanding for large deformations of soft bottlebrush polymer networks
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DOI：
10.1039/d0sm00759e
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发表时间：
2020-07-21
期刊：
影响因子：
3.4
通讯作者：
Cai, Li-Heng
中科院分区：
文献类型：
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作者：
Cai, Li-Heng
通过交联瓶刷聚合物形成的网络是一类软材料，其硬度与“水性”水凝胶和生物组织的硬度相匹配，但不含溶剂。由于它们的极端柔软性，瓶刷聚合物网络经常受到大的变形。然而，人们对分子结构如何决定网络的可扩展性知之甚少。通过实验和理论相结合的方法，我们发现网络的屈服应变γ（y）等于轮廓长度L（max）与两个相邻交联之间的瓶刷的端到端距离R的比值：γ（y）=L-max/R- 1。这种关系表明了两种状态：（1）对于刚性瓶刷聚合物，γ（y）与网络剪切模量G成反比，γ（y）类似于G（-1），这代表了以前未认识到的状态;（2）对于柔性瓶刷聚合物，γ（y）类似于G（-1/2），这恢复了传统聚合物网络的行为。我们的研究结果为软瓶刷聚合物网络的非线性力学提供了一个新的分子理解。
Networks formed by crosslinking bottlebrush polymers are a class of soft materials with stiffnesses matching that of 'watery' hydrogels and biological tissues but contain no solvents. Because of their extreme softness, bottlebrush polymer networks are often subject to large deformations. However, it is poorly understood how molecular architecture determines the extensibility of the networks. Using a combination of experimental and theoretical approaches, we discover that the yield strain gamma(y)of the network equals the ratio of the contour lengthL(max)to the end-to-end distanceRof the bottlebrush between two neighboring crosslinks:gamma(y)=L-max/R- 1. This relation suggests two regimes: (1) for stiff bottlebrush polymers,gamma(y)is inversely proportional to the network shear modulusG,gamma(y)similar to G(-1), which represents a previously unrecognized regime; (2) for flexible bottlebrush polymers,gamma(y)similar to G(-1/2), which recovers the behavior of conventional polymer networks. Our findings provide a new molecular understanding of the nonlinear mechanics for soft bottlebrush polymer networks.