This paper presents a new class of nonlinear optical (NLO) polyimide for second harmonic generation (SHG). This new class of NLO polyimide consists of 2,4-diamino-4‘-nitroazobenzene (2R-DIAMINE) with 3,3‘4,4‘-benzophenonetetracarboxylic dianhydride, in which the NLO dipole moment is aligned transverse to the main chain. 2R-DIAMINE was prepared from m-phenylenediamine with p-nitroaniline. The time dependence of the decay was found to be well-fitted by a Kohlrausch−Williams−Watts stretched exponential function. The difference of the orientational relaxation among the samples with different glass transition temperatures can be compared using the scaling relation of τ = A‘ exp[(T 0 − T)/T] in which τ is the relaxation time and T 0 is the effective transition temperature for SHG activity. T 0 is in good agreement with the corresponding glass transition temperature. Enhanced orientational stability of the aligned NLO chromophore is ascribed to the rigid structure of the polyimide backbone. For the orientational relaxation at 100 °C, a relaxation time of over 50 years could be estimated, and a relaxation time of 3.8 years could be obtained at a higher temperature of 150 °C.

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Novel nonlinear optical (NLO) network polyurethane of lysine triisocyanate (LTI) with 44N-(2-hydroxyethyl)-N-methylaminol-3'-(hydroxymethyl)azobenzene (AZODIOL) dye as a NLO-phore has been prepared for second harmonic generation (SHG). A soluble prepolymer of LTI with AZODIOL was prepared, and then a thin prepolymer film was spun-cast on an indium tin oxide coated glass substrate. Two types of poling were carried out. One-step poling process: while high voltage between 5.0 and 8.0 kV was applied to the corona wire, the sample film was heated up and held at a temperature range of 70-190 "C for 10 min and then cooled down to room temperature for 40 min. Two-step poling process: while high voltage was applied to the corona wire, the sample was heated up and held at 90 "C for 1 h and then heated up again and held at a temperature range of 90-190 "C for 30 min. Then the sample was cooled down to room temperature while applying the poling field. The effects of the above poling condition and storage time and thermal annealing on SHG activity are investigated in connection with polymer structure. Better long-term thermal stability of SHG at room temperature can be obtained for the sample prepared by a two-step poling process. This better thermal stability is interpreted to be due to the smaller free volume for that sample.

Novel regular network polyesters were prepared from pentaerythritol (Xp) and aliphatic dicarboxylic acids of different numbers of methylene groups (HOOC(CH2) n - 2COOH, n = 4, 6, 8, 9, 10, 12, 14, 16, and 20). Prepolymer prepared by melt polycondensation was cast from dimethylformamide solution and postpolymerized at 270 °C for various times to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The network polyesters obtained were characterized by infrared absorption spectra, wide angle X-ray diffraction analysis, density, thermomechanical analysis, differential scanning calorimetry, tensile test, water absorption, and alkali hydrolysis. The enzymatic degradation estimated by weight loss of the network polyester films in a buffer solution of various kinds of lipases at 37 °C was studied. The enzymatic degradation of Xpn films was compared with that of the network polyester films of glycerol with various aliphatic dicarboxylic acids reported earlier. After a 6 day incubation in Rhizopus delemar lipase solution, the weight loss was hardly observed for Xp4−8, while it increased gradually for Xp9−14 and showed the maximum weight loss of 13 g/m2 for Xp14; then the weight loss decreased abruptly for Xp16−20. Other lipases of porcine pancreas and Candida rugosa hardly degraded Xpn films.