Self-diffusion method for broadband reflection in polymer-stabilized cholesteric liquid crystal films

Abstract

ABSTRACT Chiral nematic liquid crystal (N*-LCs) films with wide pitch gradients covering the near infrared (NIR) region are facilely obtained by a simple controlling diffusion method. The polymer network can not only fix the orientation of N*-LCs, but also serves as a diffusion channel for substances, and has excellent compatibility. First, in the design of the pre-polymerisation (Incomplete polymerisation) layer, mainly by controlling the content of polymerisable monomer and UV-absorbing dyes in N*-LCs, a polymer network with density gradient distribution and suitable for material diffusion is formed, and the substrate of the oil repellent layer on the side of the low-density polymer network is easier to be peeled off. Then, nematic liquid crystals are injected between the pre-polymerisation layer and another oriented glass substrate. Due to the large concentration difference of chiral compounds and UV-327 between the two liquid crystals, the gradient distribution of spacing is formed by diffusion. Because of the gradient distribution of the UV-327, the gradient distribution of the pitch is further increased after polymerisation again. Finally, the effect of the UV-327 on the polymer network of the pre-polymerised layer is observed using SEM. Thus, a new method for reflective broadband in the near-infrared region is proposed.