Spectroscopic investigation of light induced response of a Cyano Azobenzene polymer

Abstract

In this paper, absorption spectra of both solution and films of cyano azobenzene polymer are investigated. The analysis of overlapped absorption spectra of polymer, related to trans and cis isomers, shows that the population of cis isomers is higher than trans isomers. It means that, cyano azobenzene molecules have a folded structure in polymer, in thermal equilibrium. Presence of cyano molecules causes this folded structure. Illumination of polymer films, prepared by THF solvent, with light of diode pumped solid state laser, results in increasing the population of isomers and their absorption peaks, due to trans-cis and cis-trans photoisomerization process. Then, Isopropanol is added to solution to enhance the freedom degree of molecules. So, the population of trans isomers in films and solutions, prepared by THF+Isopropanol are higher than trans isomers in films prepared only by THF. The illumination of polymer films prepared by THF+Isopropanol changes the concentrations of isomers due to photoisomerization process.