Epoxy-based azo polymers: synthesis, characterization and photoinduced surface-relief-gratings

Epoxy-based azo polymers with three kinds of backbones, different types of azo chromophores, and selected degrees of functionalization (DFs), were synthesized through a post-polymerization azo-coupling scheme. The T(g)s of the azo, polymers were found to be considerably influenced by the substituents on the 4-positions of the azobenzene units and increased with the increase of the DFs of the polymers. Surface-relief-gratings (SRGs) were induced on the polymer films by interferenced Ar+ laser beams. With the same irradiating light intensity and approximately equal film thickness, the rates of SRG formation were found to be significantly dependent on the electron-withdrawing groups on the 4-positions of the azobenzene units. For the polymers with the same type of azo chromophores and backbone structure, the inscription rates increased with the increase of the DFs. Meanwhile, the backbone structure also exhibited some effect on the inscription rates through the ways such as changing chromophore loading density or main-chain rigidity. (C) 2002 Elsevier Science Ltd. All rights reserved.