School of Materials Science and Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
Department of Material Science and Engineering, and Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Peking University , Beijing 100871, P. R. China.
ACS Appl Mater Interfaces. 2018 Feb 7;10(5):4961-4970. doi: 10.1021/acsami.7b16001. Epub 2018 Jan 17.
Hierarchically arranged stripes of photoswitchable liquid crystal polymers (LCPs) containing azobenzene moieties were conveniently crafted via a flow-enabled self-assembly (FESA). Interestingly, by subjecting a drop of LCP solution to dry in a restricted geometry comprising two nearly parallel plates with a stationary upper plate and a movable lower plate that programmably traveled in a "stop-and-move" manner during the FESA process, photoswitchable LCP stripes were yielded, displaying two modes of deposition, namely, periodic primary stripes of large dimensions and regularly spaced secondary stripes of small dimensions situated between adjacent primary stripes (i.e., forming hierarchical LCP stripes). Notably, these hierarchical azobenzene moieties-containing stripes demonstrated sequential photoinduced reversible phase transition (i.e., photoswitching) due to the thickness difference between primary and secondary stripes. A UV light-induced expansion effect was observed on the LCP stripes. Clearly, such rapid creation of hierarchical stripes by FESA represents a robust means of organizing polymers, nanoparticles, colloids, DNA, etc. into complex yet ordered patterns over a large area in a simple and controllable manner for potential use in surface relief grating, photoactuators, photoswitchable devices, antifake labels, etc.
通过一种可实现流动的自组装（Flow-enabled self-assembly，FESA），方便地制备了含有偶氮苯部分的分级排列的光致变色液晶聚合物（LCP）条纹。有趣的是，通过将一滴 LCP 溶液在由两个几乎平行的板组成的受限几何形状中干燥，其中上板固定，下板可移动，并在 FESA 过程中以“停-动”方式可编程移动，得到了光致变色 LCP 条纹，其显示了两种沉积模式，即大尺寸的周期性初级条纹和位于相邻初级条纹之间的小尺寸规则间隔的次级条纹（即形成分级 LCP 条纹）。值得注意的是，由于初级条纹和次级条纹之间的厚度差异，这些含有分级偶氮苯部分的条纹表现出顺序光致可逆相转变（即光致开关）。观察到 LCP 条纹上存在 UV 光诱导的膨胀效应。显然，通过 FESA 快速创建分级条纹代表了一种强大的方法，可以将聚合物、纳米粒子、胶体、DNA 等组织成复杂但有序的图案，在大面积上以简单可控的方式进行，可用于表面浮雕光栅、光致动器、光致变色器件、防伪造标签等。
