New polyurethanes and polyesters for second-order nonlinear optical applications.

New polymers for second-order nonlinear optical (NLO) applications were synthesized and characterized. They were distinguished by the presence of chromophore groups, with various mol. hyperpolarizability values, used as pendants on substantially rigid backbones. The polymers were prepd. through the reaction of tolylene-2,4-diisocyanate, or a suitable alkyloxyphthaloyl dichloride, with the N,N-diethanol-4-(phenyl) group azo-linked to a nitrofluorenone, nitrostilbene, nitrooxadiazole, or nitrothiadiazole moiety. The polymers exhibited good thermal stability, high glass-transition temps., and an absence of crystallinity. The second-order NLO properties of thin, transparent poled films, prepd. by spin coating and thermal corona poling, were investigated for some of the polymers. The second harmonic coeffs., ranging between 18 and 25 pmV, depended more on the alignment of the chromophore groups along the direction of the poling field than on their mol. hyperpolarizability. The ternporal stability of the NLO properties of the polymers was also investigated.