Easily crosslinkable side-chain azobenzene polymers for fast and persistent fixation of surface relief gratings

Abstract

A series of side-chain azobenzene (azo) homo- and copolymers with easily crosslinkable N-hydroxysuccinimide carboxylate-substituted azo moieties and relatively low glass transition temperatures were synthesized for rapid and persistent fixation of surface relief gratings (SRGs). These azo polymers exhibited good thermal stability and their films proved easily crosslinkable within 4–15 min with 1,6-hexanediamine under mild conditions with the crosslinking rates of copolymer films being faster than homopolymer films. Moreover, the formation speed and saturation modulation depth of the photoinduced SRGs increased both with a decrease in the flexible spacer length in azo homopolymers and with an increase in the azo contents in copolymers. Furthermore, considerably stabilized high quality SRGs were obtained after their post-fixation by crosslinking, as revealed by the negligible or rather small change of both the modulation depth of the crosslinked SRGs upon their exposure to high temperatures or organic solvents and the transparency of the crosslinked polymer films.