Control of Helical Orientation in Chiral-Nematic Liquid Crystals by Auxetic Structures

Abstract

Chiral-nematic liquid-crystalline elastomers (N*LCEs) have a helical molecular orientation exhibiting Bragg reflection at a certain wavelength matched with the helical pitch. Moreover, their helical pitch, i.e., wavelength of the selective reflection, is sensitively changed by mechanical stimuli. We have proposed that this phenomenon is useful to visualize stress and strain applied to the materials. In this study, we developed a N*LCE with an auxetic structure, which shows unique mechanical deformation behavior. The change in helical orientation of N*LCEs due to the pseudo-biaxial stretching of the Auxetic structure was discussed. As a result, the helical pitch length of liquid crystal molecules is significantly reduced, and the helical orientation is maintained.