The photodegradation of a variety of donor-acceptor-substituted azobenzene nonlinear optical chromophores has been studied. The variables examined that influence the rate of degradation include chromophore and host polymer structure, irradiation wavelength, temperature, and atmosphere.

The photodegradation of the azobenzene chromophore DR1 {4-[N-ethyl-N-(2-hydroxyethyl)amino]-4(?)-nitroazobenzene]} incorporated as a side chain or as a guest in a poly(methyl) methacrylate host has been evaluated as a function of wavelength, temperature, and the atmospheric environment. The effects of these variables on the lifetime of DR1-based electro-optic devices is quantified.

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The wavelength dependence of the one-photon absorption-induced photodegradation rate has been measured from the visible to the near IR for a variety of electro-optic chromophore-doped polymers. Systematic behavior is identified. The lifetime of the electro-optic activity is found to increase exponentially over 4-6 orders of magnitude for wavelengths ranging from peak of absorption, typically in the visible, to ~1000 nm. Many popular chromophores developed for electro-optics over the past 10 years are compared.

Rotational dynamics of nonlinear optical chromophores embedded in amorphous polymer films were studied using second harmonic generation. Corona poling was used to orient the chromophores into the bulk noncentrosymmetric structure required to observe second-order nonlinearity. Electric field effects were examined by simultaneously measuring the second harmonic signal (during and following poling) and surface voltage decay (following poling). It is found that for short times the residual field following poling retards chromophore reorientation. A mathematical model that describes the rotational Brownian motion of chromophores in a polymer matrix is developed to simulate the field-dependent behavior. The electric field effects can therefore be deconvoluted from the Brownian motion to reveal information concerning local mobility in polymers. Further applications of the model in distinguishing the post-poling electric field effects and in computing the local free volume and viscosity are discussed. A first attempt is made to realize the contributions of the residual surface voltage, field-induced bulk charges, and thermally injected charges to the rotational motion of the chromophores. The magnitude of the local free volume and the local viscositytemperature behavior in a doped poly(methy1 methacrylate) system are estimated and compared with those predicted by the Doolittle-Williams-Landel-Ferry equation. IntroductionOver the past decade, nonlinear optical (NLO) polymers have been used for optical applications such as waveguides,l-3 optical modulator^,^ optical memory tora age,^ and holography.-Conventionally, inorganic crystals were used for these applications because of their high nonlinear optical performance. However, long times and delicate controls are required to grow crystals in the large sizes and optimized molecular structures needed for NLO