Influence of Methyl Substituents on Azo-Dye Photoalignment in Thin Films

摘要

Photoalignment of azo dyes derived from salicylic acid in thin films (80-200 nm) was studied upon irradiation with polarized light (lambda(max) = 457 nm). It is shown that different trends of molecular reorientation, i.e., in the layer plane or orthogonal to it, are observed depending on the position of the methyl substituent in the dye structure. A new distribution parameter Z that allows the portion of molecules reoriented in the layer plane during exposure to be determined is introduced. The novel azo dye potassium 3,7-bis[1-(4-hydroxy-3-carboxylate)phenylazo]-5,5'-dioxodibenzothiophene was synthesized. Its molecules are photoaligned in the layer plane upon irradiation with polarized light.