Feng Wei, Broer Dirk J, Grebikova Lucie, Padberg Clemens, Vancso Julius G, Liu Danqing
SCNU-TUE Joint Lab of Devices Integrated Responsive Materials , South China Normal University , No. 378, West Waihuan Road, Guangzhou Higher Education Mega Center , Guangzhou 510006 , China.
Materials Science and Technology of Polymers, Faculty of Science and Technology, MESA+ Institute for Nanotechnology , University of Twente , Enschede 7500 AE , The Netherlands.
ACS Appl Mater Interfaces. 2020 Feb 5;12(5):5265-5273. doi: 10.1021/acsami.9b11928. Epub 2019 Sep 6.
Surface topography variations of liquid crystal networks in their functional coatings provide unique properties in these systems. Chiral-nematic polymer coatings self-organize in a fingerprint texture with the molecular helices parallel to the substrate with alternating domains of molecular units with parallel and perpendicular director orientation as controlled by the concentration of a reactive chiral additive. Driven by surface-tension differences and altered by anisotropic polymerization shrinkage, the coating may form hills and valleys hundreds of nanometers in size with different molecular alignment. The director orientation in the corrugations could be controlled by monomer diffusion during polymerization. Polymerization in the presence of a dichroic dye gives topographic elevations in which the molecules are oriented along the normal. Polymerization by means of a dichroic photoinitiator gives topographic elevations in which the molecules align parallel to the surface. By balancing the monomer diffusion and anisotropic polymerization shrinkage, relatively flat surfaces are also achieved. The different surfaces exhibit distinct topographical deformations when subjected to external stimuli, such as an AC electric field. This method can be universally extended to LC polymers with other alignment configurations.
液晶网络在其功能涂层中的表面形貌变化为这些体系提供了独特的性能。手性向列型聚合物涂层以指纹纹理自组装，分子螺旋平行于基底，分子单元的交替区域具有平行和垂直的指向矢取向，这由反应性手性添加剂的浓度控制。在表面张力差异的驱动下，并因各向异性聚合收缩而改变，涂层可能形成数百纳米大小、具有不同分子排列的山丘和山谷。波纹中的指向矢取向可在聚合过程中通过单体扩散来控制。在二色性染料存在下进行聚合会产生地形凸起，其中分子沿法线方向取向。通过二色性光引发剂进行聚合会产生地形凸起，其中分子平行于表面排列。通过平衡单体扩散和各向异性聚合收缩，也可实现相对平坦的表面。当受到外部刺激（如交流电场）时，不同的表面会呈现出明显的地形变形。这种方法可普遍扩展到具有其他排列构型的液晶聚合物。
