Abstract Main chain liquid crystalline polymers (MCLCP) offer strong potential to exhibit auxetic properties. However, the first synthesized molecules did not show the expected results. To address this issue, simulation provides an interesting advantage as it can grasp the molecular reasons why the auxetism is not reached, and thus it can guide the synthesis of successful candidates. However, the crucial step of validation is mandatory. In this study, we report the simulation of MCLCP at the coarse-grained level. Interactions are represented by an hybrid Gay-Berne/Lennard Jones (GB/LJ) potential which is particulary adapted in the simulation of anisotropic systems. Energies stemming from different configurations of pairs of ellipsoids are computed at the MP2 level, and are fitted using the GB potential. The methylene groups are represented by spheres whose interactions are depicted by the LJ potential. Molecular dynamics in the NPT ensemble (number of particles, pressure and temperature are kept constant) are thus carried out beginning at 800 K to 375 K, by cooling the system by 25 K steps. It is shown that the smectic A phase emerges at about 500 K, and the smectic B phase at about 425 K. Such mesophases occur without the use of any external stimulus. These findings pave the way to simulate LCP which have been specifically designed to potentially exhibit auxetic properties.

中文翻译：

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使用 Gay-Berne/Lennard-Jones 混合模型模拟主链液晶聚合物

摘要 主链液晶聚合物 (MCLCP) 具有展现拉胀性能的强大潜力。然而，第一个合成的分子并没有显示出预期的结果。为了解决这个问题，模拟提供了一个有趣的优势，因为它可以掌握未达到 auxetism 的分子原因，从而可以指导成功候选者的合成。但是，验证的关键步骤是强制性的。在这项研究中，我们报告了粗粒度级别的 MCLCP 模拟。相互作用由混合 Gay-Berne/Lennard Jones (GB/LJ) 势表示，特别适用于各向异性系统的模拟。源自不同配置的椭圆体对的能量在 MP2 级别计算，并使用 GB 势进行拟合。亚甲基由球体表示，其相互作用由 LJ 势描述。NPT 系综中的分子动力学（粒子数、压力和温度保持恒定）因此从 800 K 到 375 K 开始，通过 25 K 步长冷却系统。结果表明，近晶 A 相出现在大约 500 K，而近晶 B 相出现在大约 425 K。这种中间相在不使用任何外部刺激的情况下发生。这些发现为模拟 LCP 铺平了道路，LCP 专门设计用于潜在的拉胀特性。结果表明，近晶 A 相出现在大约 500 K，而近晶 B 相出现在大约 425 K。这种中间相在不使用任何外部刺激的情况下发生。这些发现为模拟 LCP 铺平了道路，LCP 专门设计用于潜在的拉胀特性。结果表明，近晶 A 相出现在大约 500 K，而近晶 B 相出现在大约 425 K。这种中间相在不使用任何外部刺激的情况下发生。这些发现为模拟 LCP 铺平了道路，LCP 专门设计用于潜在的拉胀特性。