Abstract: A process for the preparation of a thermostable polyester which is insoluble in tetrachloroethane and consists of about 40 to 200 units, said polyester having units of the formula ##STR1## combined with units of the formula ##STR2## wherein Ph is ##STR3## AND BOTH R radicals are methyl on some units and both R radicals are phenyl on the balance of the units, said methyl units comprising 5-30 mole percent of the total R-containing units which comprises heating and condensing in the absence of a catalyst 4,4'-dihydroxytetraphenylmethane having a melting point of at least 295.degree. C together with 2,2-bis-(4-hydroxyphenyl)-propane and terephthalic or isophthalic acid dichloride until there is prepared said polyester which is insoluble in tetrachlorethane.

Abstract: In a process for the manufacture of a polyimide from a polyamide carboxylic acid solution by cyclodehydration of the polyamide carboxylic acid, the improvement which comprises carrying out said cyclodehydration in the presence of a nitrogen containing compound selected from the group consisting of quinoline, isoquinoline, mono-substituted alkyl pyridines, dialkyl substituted pyridines, mono-substituted alkyl quinolines, dialkyl substituted quinolines, monoaralkyl substituted quinolines, diaralkyl substituted quinolines, monoalkyl substituted isoquinolines, dialkyl substituted isoquinolines, monoaralkyl substituted isoquinolines, diaralkyl substituted isoquinolines and mixtures thereof.