Epoxy-based polymers containing methyl-substituted azobenzene chromophores and photoinduced surface relief gratings

Series of epoxy-based polymers functionalized with methyl-substituted azobenzene chromophores have been designed and synthesized. The polymers synthesized were characterized by the spectroscopic methods and thermal analysis. Surface relief gratings (SRGs) were photofabricated on thin films of the azo polymers by exposure to an interference pattern of coherent Ar+ laser beams. The methyl substitution in the ortho-positions of the azo groups significantly influences the SRG inscription rates. The inscription rates decrease as the number of the methyl substituents increases. The rates are also related with the positions of the methyl substitution on the azo chromophores. The methyl substitution in the ortho-positions of the azo groups on anilino sides shows a more significant effect to decrease the inscription rates. Meanwhile, the type of the electron withdrawing groups in the para-positions of the azobenzene units also shows a significant effect on the SRG inscription rates.