基于分子动力学模拟的主链型液晶聚合物的新模型

在传统的Gay-Berne (GB)/Lennard-Jones (LJ)模型的基础上，发展了一种用于模拟半刚性主链型液晶聚合物(LCP)的分子级模型，命名为Solo-LJ-SP-GB 模型.单一的LJ联合体和非线性弹簧被用于描述LCP分子中的间隔体.用分子动力学模拟半刚性主链型LCP系统(该系统由169条分子链组成，每两个刚性体之间的间隔体个数为6)时，该模型所需的计算时间不到传统的GB/LJ 模型所需时间的十分之一，大大地提高了计算效率.通过采用该模型模拟半刚性主链型LCP的相变问题，观察到了与半刚性主链型LCP分子中间隔体个数相关的热力学的奇偶效应以及从等方相到向列相的相转变过程.这些模拟结果与当前的试验结果相当符合，从而表明了该模型可以较为准确地描述出半刚性主链型LCP的结构特性. 关键词： Solo-LJ-SP-GB模型 液晶聚合物 分子动力学模拟

A new molecular model for main-chain liquid crystalline polymers based on molecular dynamics simulations

This paper has derived a new molecular model for simulating semi-rigid main-chain LCPs (liquid crystalline polymers) based on the traditional GB (Gay-Berne)/LJ (Lennard-Jones) model, named Solo-LJ-SP-GB model. A single LJ unit and two nonlinear springs have been firstly used to describe the flexible spacers between GB units in the LCPs. Using the current model, the simulation time is less than 10% of that spent by using the traditional GB/LJ model, when simulating the semi-flexible main-chain LCP of 169 molecular chains with 6 flexible spacers between neighboring GB units, which greatly enhances the computational efficiency. Through using the current model to study the phase behaviors of semi-flexible main-chain LCPs, the odd-even effects of thermodynamic properties depending on the number of flexible spacers and the phase transition from isotropic to liquid crystalline have been observed, which agrees well with the existing experimental data and the simulation results of the traditional model. It is shown that the new model enables to describe the structural properties of semi-rigid main-chain LCPs accurately.