Helical pitch and thickness-dependent opto-mechanical response in cholesteric liquid crystal elastomers

Cholesteric liquid crystalline elastomers (CLCEs) are selectively reflective, deformable materials. We prepared CLCEs with selective reflection spanning the electromagnetic spectrum, from the visible to the mid-wave infrared (MWIR). Within these CLCEs, we systematically investigate the opto-mechanical response and expand upon observations detailed in our previous study where CLCEs with comparatively long pitch lengths do not exhibit total reflection in response to deformation (i.e., mechanically induced depolarization of the selective reflection). By systematically varying the pitch length and/or thickness of the CLCEs we isolate that total reflection in CLCEs is dependent on the number of helical pitches (N_p). Optical characterization, including polarized optical microscopy (POM), UV-vis, and FTIR spectroscopy, is complemented by X-ray scattering to uncover the mechanical origins. The tunable and reversible optical properties of CLCEs position them as promising candidates for adaptive optics, sensors, tunable reflectors, and reconfigurable photonic devices.