Molecular Order in a Chromonic Liquid Crystal: A Molecular Simulation Study of the Anionic Azo Dye Sunset Yellow
Molecular Order in a Chromonic Liquid Crystal: A Molecular Simulation Study of the Anionic Azo Dye Sunset Yellow
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DOI：
10.1021/ja102468g
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发表时间：
2010-06-09
影响因子：
15
通讯作者：
Wilson, Mark R.
中科院分区：
文献类型：
--
作者：
Chami, Fatima;Wilson, Mark R.
我们在水溶液中对一种慢性液晶材料（日落黄）的分子秩序进行了详细的原子模拟研究。自组装发生在稀溶液中，形成堆叠聚集体，表现出头尾堆叠和反平行偶极子顺序的偏好。这一特性与溶液浓度和骨料粒度无关。发现堆栈是动态实体，其中旋转转变（翻转）可以发生在反平行和平行构型之间。当浓度与日落黄的向列相相匹配时，模拟结果显示出具有松散六边形填料的色柱，柱间距离为2.36 nm。钠离子的部分缩聚发生在一个慢性堆叠周围，钠离子有两个首选的结合位点，对应于与磺酸基的氧的强结合和堆叠中一对分子之间的桥接位点。对于3个和8个分子的堆栈，获得了一个分子与7 kBT堆栈的自由结合能的值，二聚体结合能的值略大（额外的2 kJ mo1-1），表明聚集近似等轴。
We have carried out a detailed atomic simulation study of molecular order within a chromonic liquid crystalline material (sunset yellow) in aqueous solution. Self-assembly occurs in dilute solutions to form stacked aggregates, which show a preference for head-to-tail stacking and antiparallel dipole order. This feature is independent of solution concentration and aggregate size. Stacks are found to be dynamic entities in which rotational transitions (flips) can occur between antiparallel and parallel configurations. At a concentration matching the nematic phase of sunset yellow, the simulations show chromonic columns with a loose hexagonal packing and an intercolumn distance of 2.36 nm. Partial condensation of sodium ions occurs around a chromonic stack, with two preferred binding sites identified for sodium ions, corresponding to strong binding with the oxygens of a sulfonate group and a bridging site between a pair of molecules in a stack. A value for the free energy of binding of a molecule to a stack of 7 kBT was obtained for stacks of three and eight molecules, with a slightly larger value (additional 2 kJ mo1-1) obtained for the dimer binding energy, indicating that aggregation is approximately isodesmic.