ESR and Optical Study of Photo-Orientation in Azobenzene-Containing Liquid-Crystalline Polymer

We report a comprehensive experimental study of photoinduced processes in azobenzene-containing liquid-crystalline polymer. The kinetic and optical characteristics of the photoisomerization reaction and photo-orientation process have been determined. The spin probe technique has been used to elucidate the details of orientation order and rotational mobility of molecular fragments within the liquid-crystalline polymer. The evolution of orientation order parameters ⟨<i>P</i>₂⟩, ⟨<i>P</i>₄⟩, and ⟨<i>P</i>₆⟩ in the course of photoinduced ordering of the material as well as the change of liquid-crystalline domain sizes have been studied quantitatively. The obtained experimental results are compared with the predictions of the existing models of photo-orientation