Stimuli‐Responsive Light‐Diffusing Polarizers Self‐Assembled of Liquid Crystals and Polymers

Abstract

Light‐diffusing polarizers of liquid crystal (LC)/polymer composites are fabricated via a self‐assembly process. The transmittance has a polarization extinction ratio more than ten and is controlled electro‐ or thermo‐responsively. Such stimuli responsiveness results from unidirectionally oriented, highly rotatable LCs existing in LC‐rich domains. The polarizers are photoinduced self‐organizable, electro‐driven controllable, and wavelength adjustable. The structures comprise (sub) micrometer‐long, narrow domains of LC and isotropic polymer phases, and some LCs are oriented perpendicular to the domain boundaries. Such LC orientation becomes self‐assembly ordered through photopolymerization‐induced phase separation (PPIPS), performed by nonuniform photoirradiation with direct or Fourier‐transformed speckle‐pattern projection. The polarization extinction ratio of light diffusion increases, as the compositional ratio of urethane prepolymers increases or the photoirradiation becomes more intense. LCs are found to be oriented more uniaxially in the LC‐richer (polymer‐poorer) phases. The uniaxially oriented LCs contribute to the optical polarization of light diffusion. The electro‐response time of polarization change is the order of 100 ms and microscopically caused by LC reorientation behavior in LC‐rich domains among open polymer networks. Two different light‐source wavelengths can be chosen for PPIPS by adjusting photoinitiators. The light‐diffusing polarizers extend photonic application range from the points of view of users and manufacturers.