SYNTHESIS AND PROPERTIES OF 2 CROSS-LINKED POLYMERS WITH STABLE NONLINEAR-OPTICAL PROPERTIES

Two kinds of crosslinked polymers, containing 4-(4'-nitrophenylazo) an iline chromophore groups, were synthesized. Crosslinked polyacrylate w as synthesized by polymerization of Dispersed Red-19 (DR-19) diacrylat e, whereas crosslinked polyurethane was obtained by the reaction betwe en (beta-hydroxy propyl acrylate-DR-1 methacrylate) copolymer and phen ol-capped isocyanate-terminated DR-19. The crosslinked polymers were c haracterized by infra-red spectra, gel content and differential scanni ng calorimetry. The crosslinked polyacrylate and the crosslinked polyu rethane exhibit glass transition temperatures at 125 and 160 degrees C , respectively. Thin, transparent, poled films of both crosslinked pol ymers were prepared by spin-coating, followed by thermal curing and co rona poling at 160 degrees C for 1 h. The second-order non-linear opti cal properties of the poled films were studied by visible light absorb ance measurement according to a one-dimensional, rigid oriented gas mo del. Long-term stability of the dipole alignment at 140 degrees C was demonstrated for the crosslinked polyurethane.