Title: Piecewise Phototuning of Self-Organized Helical Superstructures

Author: Lang Qin, Wei Gu, Jia Wei, Yanlei Yu*

Journal: Adv. Mater., 2018, 30(8), 1704941.

Abstract:

Cholesteric liquid crystals (CLCs) exhibit selective reflection that can be tuned owing to the dynamic control of inherent self-organized helical superstructures. Although phototunable reflection is reported, these systems hitherto suffer from a limitation in that the tuning range is restricted to one narrow period and the optically addressed images have to sacrifice one color in the visible spectrum to serve as the background, resulting from the insufficient variation in helical twisting power of existing photoresponsive chiral switches that are all bistable. Here, delicate patterns of three primary red, green, and blue (RGB) colors with a black background are presented, which is realized based on piecewise reflection tuning of the CLC induced by a newly designed photoresponsive tristable chiral switch. Three stable configurations of the chiral switch endow the CLC with two continuous and adjacent tuning periods of the reflection, covering not only entire visible spectrum, but also one more wide period within near-infrared region. Therefore, the concept of piecewise tuning in CLC system demonstrates a new strategy for phototunable RGB and black reflective display.

论文链接：https://onlinelibrary.wiley.com/doi/full/10.1002/adma.201704941

PDF下载：Piecewise Phototuning of Self-Organized Helical Superstructures.pdf

研究者设计了一种新型光响应三稳态手性分子，通过将两种偶氮苯连接在联萘手性中心上，使基于该材料制备的光子晶体具有超宽的颜色调控范围，能够在黑色背景上显示各色图案。偶氮苯（Azo）和含氟偶氮苯（F-Azo）在紫外光和蓝光的刺激下分别发生trans-cis和cis-trans异构化反应。当使用绿光作为刺激源时，Azo由cis回复到trans，F-Azo由trans异构化为cis。由于两种Azo在蓝绿光刺激下可产生三种异构化组合，该手性分子可以产生3种稳定构型，为胆甾相液晶提供2个调控波段,将反射波长延伸至近红外光区域来显示黑色背景。