Towards tunable defect arrangements in smectic liquid crystal shells utilizing the nematic-smectic transition in hybrid-aligned geometries
Towards tunable defect arrangements in smectic liquid crystal shells utilizing the nematic-smectic transition in hybrid-aligned geometries
复制标题
DOI：
10.1039/c2sm07415j
复制
发表时间：
2012-01-01
期刊：
影响因子：
3.4
通讯作者：
Lagerwall, Jan
中科院分区：
文献类型：
--
作者：
Liang, Hsin-Ling;Zentel, Rudolf;Lagerwall, Jan
我们生产和研究了具有混合排列的液晶壳——在一个边界是平面的，在另一个边界是同向性的——在向列相(N)和smic - a （SmA）之间发生转变。外壳显示一个动态的图案序列，细节取决于对准剂和外壳的直径和厚度。在足够直径的壳层中，我们通常会在N-SmA相变附近发现一种瞬态条纹纹理，在SmA相中稳定为平铺图案，或多或少有规则间隔的焦点圆锥域。畴的尺寸和间距随壳厚的减小而减小。而在同一边界强同向锚固和壳体尺寸较小的情况下，曲率的增加使壳体在同向阶段偏向于同向而非平面取向，从而在过渡的最后阶段趋向于完全同向取向。这是对混合排列的近晶壳的首次研究，其结果很好地证明了软物质中通过自组装形成和改造动态结构的能力。新的模式扩展了可以用球形液晶实现的拓扑缺陷阵列的范围，并且特征排列与外壳及其环境的可变参数之间的相关性开辟了可调性的途径。然而，观察到的曲率增加的强烈影响，即使对于这些相当大的外壳，表明当瞄准最吸引的约1微米或更小的胶体尺寸尺度时，选择具有不同强度的平面或同向取向取向的对准剂将变得至关重要。
We produce and investigate liquid crystal shells with hybrid alignment-planar at one boundary, homeotropic at the other-undergoing a transition between the nematic (N) and smectic-A (SmA) phases. The shells display a dynamic sequence of patterns, the details depending on the alignment agents and on the diameter and thickness of the shell. In shells of sufficient diameter we typically find a transient striped texture near the N-SmA transition, stabilising into a pattern of tiled, more or less regularly spaced focal conic domains in the SmA phase. The domain size and spacing decrease with reduced shell thickness. In case of strong homeotropic anchoring at one boundary and small shell size, however, the increased curvature favors homeotropic against planar alignment in the smectic phase, and the shell then tends to adapt to complete homeotropic alignment at the final stage of the transition. This is the first study of hybrid-aligned smectic shells and the results constitute a beautiful demonstration of the capacity for dynamic structure formation and reformation via self-assembly in soft matter. The new patterns extend the range of arrays of topological defects that can be realised with liquid crystals in spherical morphology and the correlation between the feature arrangements and the variable parameters of the shell and its environment opens a route towards tunability. However, the observed strong impact from increasing curvature, even for these rather large shells, indicates that the choice of alignment agents inducing planar or homeotropic alignment with varying strength will become critical when targeting the most attractive colloidal size scale of about a micron or smaller.