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SynopsisA series of aromatic polyimide-co-amides of high thermal stability were synthesized.Low-temperature solution condensation involving aromatic diamines of varying basicity and bifunctional carboxylic acid chlorides containing preformed imide rings was employed. This approach offers several advantages over the conventional polyamic acid route. The final polymers obtained are linear, soluble, and of high molecular weight. Solution of the final polymers are stable in contrast to polyamic acid solutions, which depolymerize hydrolytically due to the neighboring-group effect. Tough, flexible films were cast from solution and required no heat cure. The properties of one polymer made by the preformed ring approach were compared to its structurally related amide and b i d e homologs.

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Phenyl‐substituted polyquinoxalines of unusually high oxidative‐thermal stability were prepared by one‐step solution condensations of aromatic tetraamines with 1,4‐bis‐(phenylglyoxaloyl)benzene and 1,3‐bis(phenylglyoxaloyl)benzene. The final polymers thus obtained show exceptionally good solubility in a variety of common organic solvents, such as chloroform, tetrachloroethane, dichlorobenzenes, and certain phenols. Polymerizations in these solvents lead to polyquinoxalines of high molecular weight at reaction rates which depend upon the solvent used. The phenylated polyquinoxalines exhibited glass transition temperatures between 253 and 317°C and polymer decomposition temperatures between 515 and 540°C, depending upon structure. Isothermal decomposition at 400°C in air showed a strong dependency of weight loss on structure. Tough, flexible films were cast from solutions.

Block 20. If different host Report) IS. SUPPLEMENTARY NOTES It. KEY WORDS (Continue an reverse side it necessar end Ientty~ by block nimber) Composites Mo~isture effects Diffusion Carbon fiber composite* 20. A bf AACT (Ceedhlua on rverse side it meosemp &W idmtl' 5 bl eek mmbeet) Mathematical models are suggested for calculating the reduced misture diffusivities in unidirectional carbon fiber reinforced composite* with hexagonal and tetragonal fiber alignment, parallel and perpendicular to the fiber direction, as a function of fiber alum fraction. DD 1 1473 "Oo O I NOV0 48t OUSOLEY8 UNCLASSIFIED S/N 010-LF414601 SECUXITY CLASIPICATIO11 OF THIS PAOt (Ma Does # EaOr*