Engineering mesophase stability and structure via incorporation of cyclic terminal groups
Engineering mesophase stability and structure via incorporation of cyclic terminal groups
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DOI：
10.1039/d1tc05954h
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发表时间：
2022-03-21
影响因子：
6.4
通讯作者：
Goodby, John W.
中科院分区：
文献类型：
--
作者：
Mandle, Richard J.;Abbott, Laurence C.;Goodby, John W.
我们报道了一些具有环状末端基团的液晶材料的表征，这导致了介晶态的温度范围的显著增强。只有短末端链的材料能够通过在由亚甲基单元组成的短间隔体末端添加大的末端环单元来支持层状中间相的形成。X射线散射实验表明，当环状端基存在时，片层近晶相的层间距明显大于等效线性未取代材料，但对取向顺序没有影响。全原子分子动力学模拟忠实地再现了实验层间距和取向有序参数，并表明环状末端单元自发地分离成扩散子层，从而导致层间距增加。分子动力学模拟预测的这种形状偏析是在晶体固体中用X射线衍射观察到的。
We report on the characterisation of a number of liquid-crystalline materials featuring cyclic terminal groups, which lead to significant enhancements in the temperature range of the mesomorphic state. Materials with only short terminal chains are able to support lamellar mesophase formation by appending a large terminal cyclic unit at the end of a short spacer composed of methylene units. X-ray scattering experiments reveal that the layer spacings of the lamellar smectic phase are significantly larger when a cyclic end-group is present than for equivalent linear unsubstituted materials, but there is no effect on orientational order. Fully atomistic molecular dynamics simulations faithfully reproduce experimental layer spacings and orientational order parameters, and indicate that the cyclic terminal units spontaneously segregate into diffuse sub-layers and thus cause the increased layer spacing. This shape segregation predicted by molecular dynamics simulations is observed in the crystalline solid state by X-ray diffraction.