Small Bandgap Type Liquid Crystalline Conjugated Polymers

Novel liquid crystalline (LC) pi-conjugated polymers with small bandgaps are synthesized. The polymers consist of benzenoid and quinonoid structures of thiophene or pyrrole and a methine moiety substituted with LC group. The polymers of 1,2, and 7 exhibit smectic mesophases and have bandgaps of 1.5, 2.5 and 2.3 eV, respectively, depending on resonance interaction between the main chain and the LC side chain. Feasibility of chemical doping and electrical conductivity of the polymers are confirmed. The polymer of 1 aligned by shear stress under LC phase showed a dichroism in fluorescence spectra. It is suggested that the present polymers are useful for not only self-alignable electrically conducting material, but also photoluminescent material with optical anisotropy.