Molecular Simulations Shed Light on Supersoft Elasticity in Polydomain Liquid Crystal Elastomers
Molecular Simulations Shed Light on Supersoft Elasticity in Polydomain Liquid Crystal Elastomers
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DOI：
10.1021/ma501836j
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发表时间：
2014-12-23
期刊：
影响因子：
5.5
通讯作者：
Zannoni, Claudio
中科院分区：
文献类型：
--
作者：
Skacej, Gregor;Zannoni, Claudio
液晶弹性体（LCE）是由液晶单元构成的高分子网络，具有弹性应变与液晶取向有序之间的耦合作用。当在各向同性相中通过聚合和交联制备，然后冷却（各向同性成因）时，多域LCE在单向拉伸下呈现出非凡的超软弹性行为，在应力应变曲线中具有平台状低弹性模量区域，然后转变成单域LCE，其中恢复标准弹性阻力。这种行为的物理机制非常有趣，但仍然是个谜。本工作探讨了其起源，再现了实验，并成功地观察到平台状的应力应变行为，通过大规模的分子等应力蒙特卡罗模拟。结果不仅表明，超软弹性背后的基本分子机制铰链上的局部域旋转和增长，但也表明，这是由一个新提出的耗散存储在各向同性成因过程中产生的缺陷的弹性能量的辅助，也解释了在主链LCE中观察到的不可逆性。
Liquid crystal elastomers (LCE)polymer networks constructed with liquid crystal unitsare functional materials characterized by a pronounced coupling between elastic strain and liquid crystalline orientational ordering. When prepared by polymerization and cross-linking in the isotropic phase, and then cooled (isotropic genesis), a polydomain LCE presents an extraordinary supersoft elastic behavior under unidirectional pulling, with a plateau-like low elastic modulus region in the stressstrain curve, before turning into a monodomain LCE where a standard elastic resistance is recovered. The physical mechanism of this behavior is of great interest, but still mysterious. This work investigates its origin, reproducing the experiment and succeeding to observe the plateau-like stressstrain behavior by means of large-scale molecular iso-stress Monte Carlo simulations. The results not only show that the basic molecular mechanism behind supersoft elasticity hinges on local domain rotation and growth but also suggest that this is assisted by a newly proposed dissipation of the elastic energy stored in the defects created by the isotropic genesis process, explaining also the irreversibility observed in main-chain LCE.