Chromophore concentration effect on holographic grating formation efficiency in novel azobenzene-functionalized polymers

Optically active photochromic poly(amideimide)s containing azobenzene side groups in the repeating unit were prepared. The polymers were designed and synthesized specifically for this work in order to evaluate chromophore concentration effect on holographic grating recording. The poly(amideimide)s with mono- and bis-azobenzene moieties were obtained via direct high temperature polycondensation and compared with respect to their ability of diffraction grating formation due to the light-induced optical anisotropy effects. Holographic gratings were fabricated in polymer films upon exposure to an interference pattern of two polarized Ar+ laser beams at 514.5 nm wavelength. Different geometries of laser beams polarization were applied. It should be emphasized that although the azobenzene moieties are rigidly connected to the polymers backbone, some of polymers exhibited the unusually high light diffraction efficiency of around 40%. The created surface relief gratings (SRGs) were successfully observed using the atomic force microscopy (AFM). AFM images show regularly defined and aligned grating structures. It should be stressed that the SRGs with maximum of relief height up to 260 nm in polyimide derivatives with side azobenzene group were observed for the first time.