Ilnytskyi Jaroslav M, Neher Dieter
Institute for Physics, University of Potsdam, Am Neuen Palais 10, 14469 Potsdam, Germany.
J Chem Phys. 2007 May 7;126(17):174905. doi: 10.1063/1.2712438.
Side chain liquid crystalline polymer with relatively long spacer was modeled on a semiatomistic level and studied in different liquid crystalline phases with the aid of molecular dynamics simulations. Well equilibrated isotropic, polydomain smectic and monodomain smectic phases were studied for their structural and dynamic properties. Particular emphasis was given to the analysis on a coarse-grained level, where backbones, side chains, and mesogens were considered in terms of their equivalent ellipsoids. The authors found that the liquid crystalline phase had a minor influence on the metrics of these objects but affected essentially their translational and orientational order. In the monodomain smectic phase, mesogens, backbones, and side chains are confined spatially. Their diffusion and shape dynamics are frozen along the mesogen director (the one-dimensional solidification) and the reorientation times increase by one to one-and-half orders of magnitude. In this phase, besides obvious orientational order of mesogens and side chains, a stable detectable order of the backbones was also observed. The backbone director is confined in the plane perpendicular to the mesogen director and constantly changes its orientation within this plane. The backbone diffusion in these planes is of the same range as in the polydomain smectic phase at the same temperature. A detailed analysis of the process of field-induced growth of the smectic phase was performed. The study revealed properties of liquid crystalline polymers that may enable their future fully coarse-grained modeling.
具有相对较长间隔基的侧链液晶聚合物在半原子水平上进行建模，并借助分子动力学模拟在不同液晶相中进行研究。研究了充分平衡的各向同性、多畴近晶相和单畴近晶相的结构和动力学性质。特别强调了在粗粒度水平上的分析，其中主链、侧链和介晶基元根据其等效椭球体进行考虑。作者发现液晶相对这些物体的尺寸影响较小，但基本上影响它们的平移和取向有序性。在单畴近晶相中，介晶基元、主链和侧链在空间上受到限制。它们的扩散和形状动力学沿介晶指向矢冻结（一维凝固），重取向时间增加一到一个半数量级。在这个相中，除了介晶基元和侧链明显的取向有序外，还观察到主链有稳定的可检测有序性。主链指向矢限制在垂直于介晶指向矢的平面内，并在该平面内不断改变其取向。在相同温度下，主链在这些平面内的扩散范围与多畴近晶相中的相同。对近晶相场诱导生长过程进行了详细分析。该研究揭示了液晶聚合物的性质，这可能使它们未来能够进行完全粗粒度建模。
