Preparation and characterization of liquid crystal composite material with electrically controlled optical states

Liquid crystal materials provide different responses to changes of external physical quantities, such as electric field, heat, magnetic field and light, and liquid crystal composites with certain response characteristics can be prepared by adding compounds with certain properties. Composite materials with information recording function can be prepared based on the prepared liquid crystal composites with responses to electric field changes. Chiral ionic liquid was synthesized. By proportionally adding the sythesized chiral ionic liquid into N*-LC, an N*-LC/chiral ionic liquid composite material was obtained, whose reflective wavelengths were electrically controlled. Experimental results indicate that the prepared N*-LC/chiral ionic liquid composite material is in an original light-transmitting state. When a direct voltage of 40 V is applied, the material is switched to a light-scattering state with a light transmittance being less than 40%. When a high-frequency alternating voltage of 40 V is applied, the material is switched into a semitransparent mirror reflecting state with a reflecting range of 400 similar to 750 nm and a light transmittance being about 45%. When the electric field is removed, the material recovers to the original state, and all these states can be memorized for some time. The liquid crystal composite material can be prepared easily without UV radiation process. The liquid crystal composite material has response characteristics to electric field, and can be electrically switched among three different states of light transmission, strong light scattering and semitransparent mirror reflection within a visible-light wavelength range. The liquid crystal composite material also has memory effect, and the switching operation is easy and convenient.