Optically isotropic nano-size encapsulation of nematic liquid crystals with a high-filling factor

The filling factor of LCs in the LC-polymer composite system is a crucial factor for the electro-optic performance of optically isotropic liquid crystal (OILC) devices. The polymerization-induced phase separation method is well-known method to fabricate the OILCs; however, this method spontaneously limits the filling factor by ∼ 40%, which is inadequately low, owing to low-LC concentration in the mixtures. To overcome such intrinsic problem, we propose an encapsulated LC which is fabricated by means of oil-in-water encapsulation. Through this approach, the filling factor of LCs is effectively increased up to 67.8% because the capsules are closely packed. Consequently, we achieve a thin-composite film of nano-size LC encapsulation whose isotropic state is reliably switched to anisotropic state in response to an external electric field with low-operation voltage (E_th = 1.4 V/μm and E_op = 4.6 V/μm), fast-response time (τ_on = 0.5 ms, τ_off = 2.2 ms), and hysteresis-free electro-optic behavior. The highly improved electro-optic performances of the proposed encapsulated LC device would give versatile applications in blooming free-form flexible displays and various tunable photonic systems.