Control of molecular-level mechano-optical response of chiral liquid-crystalline elastomers

Abstract

In chiral-liquid-crystal (LC*) phased, LC molecules are aligned helically; hence, the refractive indices of the LC* materials are altered periodically along the helical axis. The LC* materials have unique optical properties, such as selective reflection, that arise from the periodic structure of the refractive index. The wavelength of the selective reflection depends on the helical pitch as it is a Bragg reflection; therefore, we can control the reflective wavelength by controlling the helical pitch. In this study, we observed the mechano-optical behaviors of LC* elastomers, and discussed the relationship between the chemical structures of elastomers and mechano-responsive optical properties. When tensile strain was applied to the films, reversible hypsochromic shift in the reflection wavelength was induced. The results of the mechano-optical behavior observed for the LC* elastomers suggest that LC* materials have potential for application in mechanical sensors for soft robots.