Poly(2,3-diphenylphenylene vinylene) derivatives having liquid crystalline side groups

Poly(2,3-diphenylphenylene vinylene) (DP-PPV) derivatives with pendant mesogene groups were synthesized. A biphenyoxyl or cyclohexylphenoxy moiety serves as the rigid mesogen core, a methylene chain as the spacer, and a alkyl or alkoxy group as the flexible terminal group. The optical properties of the polymers were investigated by UV-vis and photoluminescent spectroscopies. The polymer films emitted green-blue photoluminescence and electroluminescence. The phase transition behaviors of the polymers were characterized by a polarized optical microscope and a differential scanning calorimeter. The monomers did not show mesophases, while the polymers exhibited a nematic phase around 170-190 °C. The aligned films exhibited dichroism in absorption and emission spectra, implying that the polymers have potential for linearly polarized LED application.