Multimodal control of liquid crystalline mesophases from surfactants with photoswitchable tails
Multimodal control of liquid crystalline mesophases from surfactants with photoswitchable tails
复制标题
DOI：
10.1039/c9tc04079j
复制
发表时间：
2019-09-21
影响因子：
6.4
通讯作者：
Evans, Rachel C.
中科院分区：
文献类型：
--
作者：
Houston, Judith E.;Kelly, Elaine A.;Evans, Rachel C.
非侵入性操纵功能材料的分级结构是光电子学、能量转换和存储设备以及药物输送系统发展中的一个关键挑战。溶致液体晶体具有长程有序性和丰富的结构，长期以来一直被用作制备多孔材料的软模板。使用诸如光的外部刺激来修改模板结构的可能性可能导致新的架构。在这里，使用小角X射线散射和偏光显微镜的组合，我们破译了含光开关尾部的中性表面活性剂的各种结构/自组装关系，这些结构/自组装关系自组织成丰富的溶致液晶中间相。通过：(I)分子结构，通过仔细选择烷基尾部/环氧乙烷头基长度；(Ii)浓度；(Iii)温度；(Iv)光异构化，实现对这些单组分体系纳米级形态的简便、多模式控制。纳米尺度的结构范围从弱集中的超溶胀片层相，更常见的溶致片层相和六方相，到纯粹的热致液晶；所有这些都可以在室温下获得。紫外光的光致异构化导致液晶相的可逆破坏，这可以通过使用掩膜进行空间控制。这项广泛的研究展示了中性光表面活性剂的多功能性，并为新的应用铺平了道路，如光响应型模板或药物输送系统。
Non-invasive manipulation of the hierarchical structure of functional materials is a key challenge in the advancement of optoelectronics, energy conversion and storage devices and drug delivery systems. Lyotropic liquids crystals, with their long-range order and a rich array of structures, have long been exploited as soft templates to prepare porous materials. The potential to modify the template structure using an external stimulus such as light could lead to new architectures. Here, using a combination of small-angle X-ray scattering and polarised optical microscopy, we decipher the various structure/self-assembly relationships of neutral surfactants bearing photoswitchable tails, which self-organise into a rich variety of lyotropic liquid crystalline mesophases. Facile, multimodal control of the nanoscale morphology of these single-component systems is achieved through: (i) molecular structure, via careful selection of the alkyl tail/ethylene oxide headgroup lengths; (ii) concentration; (iii) temperature; and (iv) photoisomerisation. The nanoscale architectures range from the weakly concentrated hyperswollen lamellar phases, the more common lyotropic lamellar and hexagonal phases, to pure thermotropic liquid crystals; all of which are accessible at room temperature. Photoisomerisation with UV light leads to the reversible destruction of the liquid crystalline phase, which can be spatially controlled through the use of a mask. This extensive study demonstrates the versatility of neutral photosurfactants and paves the way for new applications, such as photoresponsive templates or drug delivery systems.