Dynamic Infrared Reflective Filters Prepared from Cholesteric Liquid Crystalline Elastomers

Abstract

Cholesteric liquid crystalline elastomers (CLCEs) exhibit selective reflection due to a periodic variation of the refractive index throughout the thickness of the material. CLCEs can be formulated and prepared to reflect light in the UV, visible, and infrared regions of the electromagnetic spectrum by simply adjusting the concentration of the chiral species. This report details the synthesis and preparation of appropriately thick CLCEs that maximize reflection in both the short-wave and mid-wave infrared (SWIR, MWIR) regions of the electromagnetic spectrum. As elastomers, fully solid CLCEs can be mechanically deformed to tune the selective reflection. This report details approaches to tune selective reflection, including mechanical deformation, incidence angle, thermochromism, and dielectric actuation. Generally, the optomechanical response of the CLCE at longer pitch lengths (e.g., infrared reflecting) is comparatively less than that of prior examinations of analogous compositions with a shorter pitch. Furthermore, the contribution of modulus and dielectric breakdown to electromechanical response is examined.