Optical Properties of Cholesteric Liquid Crystal Elastomers under Various Stretching Conditions

Abstract

Cholesteric liquid crystal elastomers (CLCEs) exhibit both mechanical elasticity of rubber and optical characteristics of nanoscale periodic helical structures. Due to their elastic nature, mechanical deformations allow CLCEs to tune the structural color, which is called mechanochromism. Exploring the mechanochromism of CLCEs has attracted considerable research interest to date. An exclusive focus of most studies is the color shifting of uniaxially stretched CLCEs. Consequently, not much is known about the other optical properties or chiral structural behaviors at the nanoscale of CLCEs under various stretching directions. In this study, the reordering in the helical structure of CLCEs and consequential optical properties are explored when subjected to stretching along multiple axes. Beyond assessing the reflected structural color, the characteristics of circularly polarized color were also investigated. The dynamics of optical properties are observed in three distinct stretching directions, specifically uniaxial, biaxial, and out-of-plane stretching. Through the results of this study, the uniaxial stretching is confirmed that it leads CLCEs to lose their inherent circular polarization selectivity because of the helix unwinding. On the other hand, the biaxial and out-of-plane stretching modes preserve the helix and circular polarization selectivity. These results could offer a thorough comprehension of the helical structure changes caused by various stretching conditions and help with applying mechanochromic CLCEs in diverse optical applications.