de ionized water and washed also with water the moist diamine is dried overnight in a vaccum oven and contains less that 10 ppm iron sodium and chloride ions further information concerning diamines may be found in copending application ser no 105 857 filed oct 7 1987 now u s pat no 4 906 741 the disclosure of which is incorporated herein by reference a 5000 ml 3 neck flask was fitted with a stirrer condenser ice water bath thermometer and nitrogen atmosphere to the flask 250 5 g 0 75 mole of recrystallized substantially pure 2 2 bis 4 aminophenyl hexafluoropropane mw 334 along with 1000 grams freshly distilled n methyl pyrrolidone nmp was charged the mixture was agitated to get a clear solution cooling was applied and agitation was continued until the diamine solution reached about 15 degrees celsius to the cooled solution 333 grams 0 75 mole of electronic grade 2 2 bis 3 4 dicarboxyphenyl hexafluoroprpane dianhydride was charged portion wise in substantially equal intervals while the system was agitated over a forty five minute period so that the solution was maintained at 20 25 degrees celsius by the bath while the exothermic polymerization occurred the beakers used to add the diamine and dianhydride was washed with an additional 1334 grams of freshly distilled nmp which was added to the reaction flask to make a roughly 20 percent solution of polymer precurser the reaction mixture was agitated gently for twenty hours while maintaining the temperature uniformly throughout the reaction mixture at.