Fabrication of cholesteric liquid crystalline semiconductor thin films by solution process and the contribution of trifluoromethyl groups

Abstract

We have successfully fabricated cholesteric liquid-crystalline (CLC) semiconductor thin films from the mixture of dimeric and monomeric compounds based on oligo(p-phenylenevinylene) units by spin-coating method. This is the first example of solution-processed planarly orientated thin film in CLC semiconductors. The mixture exhibited a stable CLC phase at lower temperatures than the compound alone, allowing the fabrication of spin-coated CLC thin films at room temperature. Furthermore, the dimeric compound has trifluoromethyl groups that exhibited high solubility in organic solvents such as chloroform due to its improved hydrophobicity. In addition, the high hydrophobicity of the trifluoromethyl groups lowers the surface tension of the liquid-crystal material, resulting in planar orientation.