Photoreorientation in liquid crystalline side-group polysiloxane with azobenzene derivative admixture

The photoreorientation effect in thin films of a liquid crystalline side-group polysiloxane with an azobenzene derivative admixture of the pseudo-stilbene type is presented. The film is introductory homogenously aligned in a typical liquid crystal cell of 3 pm in thickness due to rubbed polyimide coatings. The molar concentration of the azobenzene derivative, calculated per monomeric mesogenic units of the polysiloxane, is equal to 0.021 M/M and corresponds to 2 wt%. The exposure with linearly polarized light results in a reorientation of the azobenzene derivative and the 4'-cyano biphenyl side groups of the liquid crystalline polymer perpendicular towards the electric field vector of the incident light. Caused due to the reorientation process the degree of order is decreased front 0.73 to 0.44.