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In this paper we present the results of ESR and photo-ESR m e a s u r e m e n t s o n Y Α l O 3 (Y Α Ρ) s i n g l e c r y s t a l s a n d p o w d e r s a m p l e s d o p e d p u r p o s e l y with about 1 at.% Nd 3+ and undoped crystals in which Er3 + was observed as residual dopant. The ESR measurements were carried out at X-band spectrometer in 4-300 K temperature range. TIe photo-ESR was performed at 5 K using a mercury arc lamp. For the Nd 3 + doped crystals the intensity of ESR signal decreased about 2 times during illumination conditions. Moreover, the calculations of the g tensor and Α Hyperfine structure parameters for Νd3+ and Er3 + were carried out.

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Representatives of a family of soluble, imidized maleimide‐terminated amide‐imide precursors for molding and composite applications were prepared and characterized. The key step was the preparation of an amine‐terminated amide‐imide intermediate that was needed in order to introduce the maleimide groups. Trimellitic anhydride (TMA) and its monoacid chloride (TMAC) were each investigated for utility in reaction with molar excesses of methylenedianiline. With TMA the limiting factor was the time‐consuming amidation reaction, which, although catalyzed with triphenyl phosphite, required 24 hr to bring to completion in hot N‐methylpyrrolidone (NMP). The use of TMAC provided a more facile route to the intermediate and, as shown by gel permeation chromatography (GPC), resulted in a narrower molecular weight range than with TMA for the final maleimide‐terminated products. The reactions were followed by carboxyl titration, and the resulting products were characterized by IR, NMR, DTA, GPC, and inherent viscosity. The relative thermal capabilities were compared by isothermal aging as thin films (250°C) and as molded bars (316°C). Physical properties were assessed on glass laminates and molded bars. Although soluble in polar solvents, the products were viscosity unstable at ambient conditions. A solution to this problem was demonstrated by the preparation of the cyclopentadiene adduct, which was viscosity stable.