A polymer microsphere-filled cholesteric-liquid crystal film with bistable electro-optical characteristics

In this paper, we promote a new polymer microsphere-filled cholesteric-liquid crystal (PFLC) system sandwiched between two flexible substrates for making a robust composite film with both bistable optical performance and high mechanical strength . The effects of the size of the polymer microspheres (PMs) and the pitch of the cholesteric liquid crystals (ChLCs) on the electro-optical performance of the as-made PFLC films were systematically investigated. Results show that the optical appearance of the optimized PFLC film can be reversibly changed between transparent and light-scattering states according to electric field by switching the ChLCs between planar (P) and focal conic (FC) states. Moreover, both P and FC states are stable for more than one year after removing the electric field, which is due to the great reduced polymer specific surface area of 1.78 m 2 /g and the spatial hindrance from the in situ thermally polymerized PMs, respectively. Aside from the long-term optical stability, the high content of the densely packed PMs also endows the PFLC film with a satisfactory shearing strength of 206.0 kPa between the top and bottom substrates, showing great potential applications in a wide range of uses, such as smart windows , electronic paper or writing tablets.