Preparation of chiral polymer/cholesteric liquid crystals composite films with broadband reflective capability for smart windows and thermal management of buildings

In this study, a new method to prepare the chiral polymer/cholesteric liquid crystals composite films with broadband reflective capability was reported. A negative dielectric anisotropy liquid crystal material was utilized as the mesogenic solvents and a chiral mesogenic monomer was employed as the chiral dopant. The chiral mesogenic monomer not only induced the liquid crystal molecules to align to form the helical structure, but also as the polymerizable monomer to be crosslinked under UV light to stabilize the pitch gradient in the materials. The UV absorbing dye was used to generate the intensity gradient of UV light and promoted the diffusion of the chiral mesogenic monomer from the backlight side to the light side. The effect of the content of the chiral mesogenic monomer and the intensity of the UV light applied during the preparation process of the composite film on the broadband reflective capability was studied systematically. The chiral polymer/cholesteric liquid crystals composite film that can reflect the light covering the wavelength from 820 nm to 2100 nm was achieved successfully and was used as the functional film in the windows for shielding part of near-infrared light to achieve the thermal management effect of buildings. This work is expected to provide a new method for the preparation of smart windows and thermal management of buildings.