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Syntheses of a series of conjugated donor-acceptor chromophores, based on a strongly electron-withdrawing heterocyclic acceptor, have led to compounds with large second-order optical nonlinearities. Incorporation of one of these chromophores into polycarbonate at 20 percent weight loading yielded, after poling at 150 volts per micrometer, a polymer film with an electro-optic coefficient, r 33 , of 55 picometers per volt at 1.313 micrometers. This value is roughly twice that of lithium niobate. A variant of one of these chromophores exhibited improved thermal stability as needed for use in polymers with higher glass transition temperatures. The chromophore was soluble in common organic solvents, had a scalar product of the dipole moment, μ, and the molecular first hyperpolarizability, β (corrected for dispersion), of roughly 5000 × 10 −48 electrostatic units, and showed less than 10 percent decomposition after heating for 20 minutes in air and at 200°C in an inert organic solvent.

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Relaxation processes in nonlinear optical modified polyimide polymers with side-chain azo chromophores having glass transition temperatures in the range of 140 < T g < 170 °C have been studied. The relaxational mechanisms of the side-chain chromophores in these polymers have been investigated above and below the glass transition by second-harmonic decay, dielectric relaxation, and differential scanning calorimetry measurements. The nonexponential relaxation in both the time and frequency domains was modeled by the Kohlrausch−Williams−Watts (KWW) function. The nonlinear relaxational behavior of these polymers can be modeled in terms of the Tool−Narayanaswamy description of glassy state behavior. It allows for the nonlinear extension of the liquid equilibrium state behavior into and below the glass transition region with an accurate prediction of the relaxation times over more than 15 orders of magnitude in time. Time−temperature scaling of the relaxation times with (T g − T)/T as the relevant scaling parameter is observed below the glass transition.

New modified polyimide polymers with pendent side group nonlinear optical (NLO) azo chromophores and moderate to high glass transition temperatures (140 °C < Te < 190 °C) have been prepared. Corona poled films of these polymers possess large nonlinear optical susceptibilities of d3J = 23 pm/V and electrooptic (EO) coefficients of ri3 -6.5 pm/V at a wavelength of X = 1.3 gm. The structural properties (glass transition, molecular weight, chromophore density) and optical properties (refractive index, optical nonlinearity) of these polyimides can easily be varied to fulfill the requirements of potential electrooptic devices. Due to the relatively high glass transition temperatures of these polymers, long-term stability of the optical nonlinearity of typically one to hundreds of years at operating temperatures of 80-100 °C is predicted from accelerated time-temperature measurements. Using a development of a phenomenological theory of the glass transition, a normalized relaxation law is proposed with (Tg -T)/T as the relevant scaling parameter.