Broadband reflection in polymer stabilized cholesteric liquid crystal films with stepwise photo-polymerization.

In this study, we demonstrate a novel method for fabricating polymer stabilized cholesteric liquid crystal (PSCLC) films with non-uniform pitch distribution by utilizing two kinds of photo-induced processes. Based on the large HTP temperature dependence of a chiral dopant, polymer networks were formed at two distant temperature points in sequence. The influence of the polymerization conditions on the reflectance properties of PSCLCs before and after polymerization was investigated. The results strongly suggest that the location and bandwidth of the reflection band can be controlled preferably by adjusting the ultraviolet light intensity and irradiation time of UV-light. In addition, the morphology of the polymer network in the composites was studied using scanning electron microscopy (SEM). A general correlation between polymerization conditions, the network morphology, and the reflective region will be outlined.