Synthesis and characterization of poly-(p-phenylene pyromellitamic acid)

Poly-(p-phenylenepyromellitamic acid)s have been synthesized over the weight average molecular weight range from 8,000 to 22,000 by reaction of pyromellitic dianhydride and p-phenylenediamine in dimethylformamide. The polymers were recovered as amorphous yellow powders having planar dimensions of 3-4 x 1-2 µm with thicknesses of 0.1-0.2 µm and contained 20-30% associated dimethylformamide. Consumption of reactants and attainment of the ultimate molecular weight of the polymer was found to occur within one minute. Thermogravimetry of the solid poly(amic acid)s was used in a method developed to determine the amount of associated dimethylformamide, to study the cyclization of poly(amic acid) to polyimide, and to study the decomposition of the polyimide in air and in argon. Viscometry and light scattering measurements showed that dimethylformamide is a poor solvent for the polymer. The intrinsic viscosity - weight average molecular weight relationship was found to be [η] = 25.22 x 10⁻⁴ M̄w⁰.⁵⁶³ The poly(p-phenylene pyromellitamic acid)s were also characterized by ultraviolet, visible, near infrared, and infrared spectroscopy; differential thermal analysis; vapor pressure osmometry; and gel permeation chromatography --Abstract, page ii