School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA.
Soft Matter. 2017 Nov 22;13(45):8542-8555. doi: 10.1039/c7sm01819c.
T-shaped bolaamphiphiles (TBA) with a swallow-tail lateral chain have been found to provide a fertile platform to produce complex liquid crystalline phases that are accessible through changes of temperature and lateral chain length and design. In this work, we use molecular simulations of a simple coarse-grained model to map out the phase behavior of this type of molecules. This model is based on the premise that the crucial details of the fluid structure stem from close range repulsions and the strong directional forces typical of hydrogen bonds. Our simulations confirm that TBAs exhibit a rich phase behavior upon increasing the length of their lateral chain. The simulations detect a double gyroid phase and an axial-bundle columnar phase which bear some structural resemblance to those found in the experiment. In addition, simulations predict two cocontinuous phases with 3D-periodicity: the "single" diamond and the "single" plumber's nightmare phase. Our analysis of energetic and entropic contributions to the free energy of phases formed by TBA with either swallow-tail or linear side-chains suggest that the 3D-periodic network phases formed by the former are stabilized by the large conformation entropy of the side-chains.
具有燕尾型侧链的 T 型两亲分子（TBA）被发现为产生复杂液晶相提供了一个有利的平台，这些液晶相可以通过温度和侧链长度和设计的变化来实现。在这项工作中，我们使用简单的粗粒化模型的分子模拟来描绘这种分子的相行为。该模型基于这样的前提，即流体结构的关键细节源于近距离排斥和氢键典型的强定向力。我们的模拟证实，随着侧链长度的增加，TBAs 表现出丰富的相行为。模拟检测到双各向同性相和轴向束状柱状相，它们与实验中发现的相具有一些结构相似性。此外，模拟预测了两种具有 3D 周期性的共连续相：“单一”金刚石和“单一”水管工噩梦相。我们对 TBA 形成的相的自由能的能量和熵贡献的分析表明，前者形成的 3D 周期性网络相是由侧链的大构象熵稳定的。
