Characterization of a side-chain liquid crystalline polymer as reversible polarization holographic material

Polymers with high optical sensitivity, short access and switching times, reversibility, and high storage densities are being developed for use as optical recording media. It was found that polymers containing azobenzene groups had these properties. Therefore, much attention was paid to the polymers containing the azobenzene group recently. The mechanism of optical anisotropy in a polymer containing azobenzene moieties in the side chain is based on the photoselective excitation of the azobenzene groups with the transition moment parallel to the light polarization. They undergo a multitude of trans-cis-trans isomerization cycles accompanied by motion of their transition moment until they fall perpendicular to the polarization of the actinic light. This results in an anisotropy induced by the orientation of the azobenzene groups. We investigated the characteristics of photoisomerization in a side-chain liquid crystalline polymer. The prepared material was side-chain polymalonic esters (PCN) with two symmetrical azobenzene groups, 4-cyanoazobenzene. A couple of ethylenoxy groups used as flexible spacers were incorporated into the azobenzene unit for improving the liquid crystalline behavior.