Chiral porous thin film/liquid crystal hybrid materials

Abstract

The orientational ordering of liquid crystal (LC) materials directly determines their optical properties. Controlling the orientational order allows the optical properties to be engineered for display and switching applications. Recent advances in LC ordering with LCs embedded in porous networks have resulted in materials with exciting new properties, enabling new display and switching technologies. A new technique called Glancing Angle Deposition (GLAD), based on conventional thin film fabrication, allows engineering of porous structures of inorganic materials in three dimensions on a nanometer scale. By impregnating the void spaces in these porous inorganics with various polymers and LCs, we have created a new type of hybrid material where the orientational order of the impregnate is controlled by the inorganic backbone structure. Optical measurements of GLAD materials with various impregnates demonstrate that simple rodlike liquid crystalline materials (nematics) are oriented by a helical inorganic backbone to form a phase similar to the chiral nematic phase seen in other (cholesteric) liquid crystals. This new hybrid material appears promising for optical switching and display applications.