Photo- and thermal switching of blue phase films reflecting both right- and left-circularly polarized light

Abstract

A new kind of blue phase (BP) liquid crystal (LC) films has been developed which could reflect both right- and left-circularly polarized light. Here a free-standing, three dimensional (3D) BP polymer template with around 2/3 the cell thickness was first fabricated by non-uniform photopolymerization of a LC mixture at BP I temperature induced by an ultraviolet light absorbing dye, in which the non-reactive components were removed to achieve a porous polymer template with a right-handed (RH) structure, retaining the 3D structure of BP I. By refilling photoresponsive and left-handed (LH) helical structure BP-LCs containing a chiral azobenzene switch into the polymer template, we finally obtain a BP-LC film with a segregation of RH and LH domains across the LC film, thereby reflecting both right- and left-circularly polarized light. Photo- and thermal switching characteristics of this BP film were investigated in detail. These special optical properties make this kind of BP-LC film interesting for great potential applications in many fields such as flexible LC displays, optical components, LC lasing, etc.