NONLINEAR-OPTICAL CROSS-LINKED POLYMERS AND INTERPENETRATING POLYMER NETWORKS CONTAINING AZO-BENZOTHIAZOLE CHROMOPHORE GROUPS

Two kinds of crosslinked polymers and one kind of interpenetrating pol ymer network (IPN) containing phenylazo-benzothiazole (BT) chromophore groups were synthesized. Crosslinked polyurethane was obtained by the reaction between (2-hydroxypropyl acrylate-BT-l methacrylate) copolym er and phenol-capped NCO-terminated BT-2, whereas crosslinked epoxy-ba sed polymer was formed by reaction between epoxy-containing BT and BT- containing aniline. IPNs based on crosslinked polyurethane/epoxy-based polymer were obtained by carrying out the above two reactions simulta neously. The crosslinked polymers and IPNs were characterized by gel c ontent, LR spectra and differential scanning calorimetry. The crosslin ked polyurethane and the epoxy-based polymer exhibit glass transition temperatures at 140 and 178 degrees C, respectively, whereas the IPN s hows two T-g at 142 and 170 degrees C. Thin, transparent poled films o f the crosslinked polymers and IPN were prepared by spin-coating, foll owed by thermal curing and corona poling at 160 degrees C for 1 h. The second-order non-linear optical properties of the poled films were st udied by a visible light absorbance measurement according to the one-d imensional rigid oriented gas model. Long-term stability of the dipole alignment at 120 degrees C was demonstrated for the three polymers. ( C) 1998 Elsevier Science Ltd. All rights reserved.