Sivaranjini B, Mangaiyarkarasi R, Ganesh V, Umadevi S
Department of Industrial Chemistry, Alagappa University, Karaikudi, 630003, India.
Electrodics and Electrocatalysis Division (EEC), CSIR - Central Electrochemical Research Institute (CSIR-CECRI), Karaikudi, 630003, India.
Sci Rep. 2018 Jun 11;8(1):8891. doi: 10.1038/s41598-018-27039-3.
A simple and effective approach for vertical alignment of liquid crystals (LCs) over a functionalized transparent flexible substrate is described. Surface characterization of this commercially available plastic substrate through X-ray photoelectron spectroscopy (XPS) and attenuated total reflection infrared spectroscopy (ATR-IR) indicated that cellulose acetate is main component of the transparent substrate. This substrate was chemically functionalized with a suitable LC compound. A trimethoxysilane terminated new rod-shaped mesogen is synthesized and covalently attached to the pre-treated film through silane condensation reaction. LC functionalization of the polymer film is confirmed through contact angle (CA), atomic force microscopy (AFM), XPS and ATR-IR spectroscopy studies. Versatility of the LC modified flexible substrates for the alignment of bulk LC sample at substrate-LC interface was assessed for nematic (N) and smectic A (SmA) phases. Remarkably, LC functionalized cellulose acetate films were found to be highly efficient in assisting a perfect homeotropic alignment of LCs (for both, a room temperature N and a high temperature SmA phase) over the entire area of the LC sample under observation indicating their superior aligning ability in comparison to their unmodified and octadecyltrimethoxysilane (OTS) modified counterparts. The demonstrated method of surface modification of flexible polymer film is easy, surface modified substrates are stable for several months, retained their aligning ability intact and more importantly they are reusable with maximum delivery.
本文描述了一种在功能化透明柔性基板上垂直排列液晶（LC）的简单有效方法。通过X射线光电子能谱（XPS）和衰减全反射红外光谱（ATR-IR）对这种市售塑料基板进行表面表征，结果表明醋酸纤维素是透明基板的主要成分。该基板用合适的LC化合物进行了化学功能化。合成了一种三甲氧基硅烷封端的新型棒状液晶基元，并通过硅烷缩合反应将其共价连接到预处理膜上。通过接触角（CA）、原子力显微镜（AFM）、XPS和ATR-IR光谱研究证实了聚合物膜的LC功能化。评估了LC修饰的柔性基板在基板-LC界面处对块状LC样品排列的通用性，用于向列相（N）和近晶相A（SmA）。值得注意的是，发现LC功能化的醋酸纤维素膜在观察到的LC样品的整个区域内，能够高效地辅助LC实现完美的垂直排列（对于室温下的N相和高温下的SmA相），这表明与未修饰的和十八烷基三甲氧基硅烷（OTS）修饰的对应物相比，它们具有卓越的排列能力。所展示的柔性聚合物膜表面改性方法简单，表面改性后的基板可稳定数月，保持其排列能力不变，更重要的是它们可重复使用且具有最大的传递效率。
