Nonlinear optical crosslinked polymers and interpenetrating polymer networks containing azo-benzothiazole chromophore groups

Abstract

Two kinds of crosslinked polymers and one kind of interpenetrating polymer network (IPN) containing phenylazo-benzothiazole (BT) chromophore groups were synthesized. Crosslinked polyurethane was obtained by the reaction between (2-hydroxypropyl acrylate-BT-1 methacrylate) copolymer and phenol-capped NCO-terminated BT-2, whereas crosslinked epoxy-based 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 simultaneously. The crosslinked polymers and IPNs were characterized by gel content, IR spectra and differential scanning calorimetry. The crosslinked polyurethane and the epoxy-based polymer exhibit glass transition temperatures at 140 and 178°C, respectively, whereas the IPN shows two T g at 142 and 170°C. Thin, transparent poled films of the crosslinked polymers and IPN were prepared by spin-coating, followed by thermal curing and corona poling at 160°C for 1 h. The second-order non-linear optical properties of the poled films were studied by a visible light absorbance measurement according to the one-dimensional rigid oriented gas model. Long-term stability of the dipole alignment at 120°C was demonstrated for the three polymers.