Precise Control of the Wavelengths of the Reflection Bands of the Cholesteric Liquid Crystal Polymer Network Patterns

Cholesteric liquid crystal polymer network (CLCN) patterns have been applied in decorative and anticounterfeiting applications because of their vivid structural colors. In this article, a cholesteric liquid crystal (CLC) mixture with photochromism property was prepared using a chiral dopant derived from azobenzene. The ortho-methyl groups can stabilize the Z-form of the azobenzene group. Due to the low isomerization energy barrier of the azobenzene group, the photochromism can be accomplished within 10 s. Therefore, CLCN patterns should be able to be prepared on coating lines. The selective Bragg reflection band of the CLCN film can be controlled precisely with the addition of a non-photoisomerizable chiral dopant. Based on these, a two-step approach was developed for the preparation of colorful CLCN patterns. Moreover, a CLCN pattern composed of both left- and right-handed helical CLCNs and a one-dimensional CLCN grating with a relief structure were prepared.