Resinous condensation polymers of polycarboxylic acid compounds and aromatic diprimary amines comprising diamino-t-butylbenzens are described. In particular, film-forming polyamides, polyimides and polyamide-imides and their copolymers made using diamino-t-butylbenzenes which have amino groups meta or para to each other on a benzene ring are described. These polymers have some solubility in organic solvents such as N-methylpyrrolidone, a high glass transition temperature, excellent thermal stability, and are useful in films, fibers and composites, and in the electronics industry as electrical component substrates, protective coatings, interlevel dielectrics and the like.