Topographic localization of liquid crystals based on gradual phase separation in a polymer network for electrically tunable smart window applications

A novel approach of realizing the transmittance-tuning mechanism based on the topographic localization of the liquid crystals (LCs) within the polymer network is proposed. The photopolymerization of chiral LC (CLC)/reactive mesogen (RM) mixtures without a photoinitiator in the bulk induced the gradual phase separation of the CLC and RM, producing a submicron-scale porous morphology in the polymer network. An achiral LC, which was injected after the removal of the residual mixture, was localized in the porous polymer network. In the state without an applied voltage, the localized LC molecules were homogeneously aligned along the adjacent polymer ordering, enabling the transmissive state to be achieved. Under the applied electric field, the reorientation of the LC molecules distributed the effective refractive index to scatter the incident light. The authors' concept of localizing LC molecules in the submicron scale will be applicable for the new type of smart window applications.