Cholesteric liquid crystalline thermosets: synthesis, structure and properties of ChLCTs/precursor polymers

Abstract

The synthesis of six liquid crystalline monomers M₁–M₆ and three series of side chain cholesteric liquid crystalline polymers P₁–P₃ is described. The chemical structures of the monomers were characterized by FTIR and ¹H NMR spectroscopy. The structure–property relationships of M₁–M₆ and P₁–P₃ are discussed. Their phase behaviour and optical properties were investigated by differential scanning calorimetry and polarizing optical microscopy. The monomers M₁–M₃ exhibited cholesteric phases; M₄–M₆ showed nematic or smectic phases. The polymer series P₁–P₃ showed cholesteric phases. Experimental results demonstrated that the selective reflection of the cholesteric monomers and homopolymers shifted to the shorter wavelength region (blue shift) with increasing length of the flexible spacer. The selective reflection of the copolymers shifted to the longer wavelength region (red shift) with increasing content of nematic units.