Structure-property relationships for film-forming poly(amide imide)s

Poly(amide imide)s from dichloro-dianhydrides of tri-mellitimide-and/or pyromellitimide-N-acetic acids (TMA and PMA), linear aromatic dimimines (LAD) and/or cardo diamine (CDA), 9,9 ' -bis-phenylfluorene (series PAI-1); a similar series (PAI-II) from dichloro-dianhydride of trimellitimide-N-benzoic acid (TMB), LAD and/or CDA; and a series of coPAIs from dichloro-dianhydride of TMA and mixtures of diphenylmethane diamine (DPA) with CDA were synthesized by low-temperature reaction in dimethyl acetamide (DMAA). The state of aggregation of PAIs and coPAIs in dilute and semi-dilute solutions of DMAA was characterized by measurements of specific heat capacity in the temperature interval 150-370 K, of heats of dilution in DMAA at room temperature, and of apparent viscosity in the temperature interval 288-373 K. The state of aggregation of PAIs and coPAIs in thin films cast from DMAA solutions was characterized by wide-angle and small-angle X-ray diffraction, dynamic mechanical analysis, broad-band dielectric spectroscopy and gas transport properties. It is concluded that film-forming PAIs and coPAIs have a reasonably good potential as high-temperature dielectrics and membrane materials for gas separation.