MAIN-CHAIN 2ND-ORDER NONLINEAR-OPTICAL POLYMERS - RANDOM INCORPORATION OF AMINO SULFONE CHROMOPHORES

Several nonlinear optical (NLO) polymers with amino-sulfone azobenzene chromophores randomly incorporated into the polymer backbone have bee n synthesized by condensation polymerization techniques. The length an d content of the flexible segments are varied to study their effects o n second-harmonic generation coefficients. For comparison, a side-chai n polymer having virtually the same chromophore incorporated as a pend ant has also been prepared. The effects of polymer structure on electr ic field poling efficiency and the stability of the poling-induced dip ole alignment were studied. The results show that these main-chain, se cond-order NLO polymers, with random incorporation of the dipolar chro mophores, can be efficiently poled, yielding chi(2) as high as 300 pm/ V. The temporal stability of the poling-induced macroscopic order is d etermined by the flexibility of the polymer chains and can be greatly enhanced by cross-linking the polymer backbone.