The effect of thermal curing on the thermal expansion coefficients (TECs) and morphologies of films of PMDA-ODA (pyromellitic dianhydride-4,4'-oxydianiline) and PMDA-PDA (p-phenylenediamine) has been examined by using the techniques of FTIR (Fourier transform infrared), X-ray diffractometry, and bending beam. The TECs varied significantly with annealing temperature before the films were fully cured. The PMDA-ODA film was nearly fully cured when annealed at 300-degrees-C, while the same was true for PMDA-PDA at 250-degrees-C. The morphology of the PMDA-ODA film did not vary with annealing, while that of PMDA-PDA changed from low to relatively high ordering when annealed at temperatures from 100 to 250-degrees-C. During annealing of the PMDA-PDA film at 150-degrees-C, a substantial amount of intermolecular links formed. Some of the links disappeared when the film was further annealed at 350-degrees-C and above.
