PREPARATION OF AROMATIC POLYAMIDE POLYANIONS - A NOVEL PROCESSING STRATEGY FOR AROMATIC POLYAMIDES

The reaction of aromatic polyamides such as poly(p-phenylene terephthalamide) (PPTA) with a variety of strong bases to yield dimethyl sulfoxide (DMSO) soluble polyanions has been explored. At least 60% of the amide groups must be deprotonated to give soluble polyanions of PPTA, Little loss of molecular weight was observed under 40 °C. Solution viscosity was highly dependent on the cation, with potassium giving lower viscosity solutions than sodium. The viscosity of the PPTA solutions increased with the degree of deprotonation, suggesting an increase in chain stiffness. Addition of proton donors, such as methanol, to the reaction of base with the aromatic polyamide in DMSO significantly enhanced the rate of polymer dissolution and gave higher solubilities and lower solution viscosities. Deprotonation of dibenzoyl-p-phenylenediamine was studied as a model compound for PPTA, confirming the results from the polymer. A single-crystal X-ray diffraction study of the model compound as its dianion revealed a short C-N bond and a long C-0 bond in the amide groups indicative of increased conjugation through the backbone chain. Properties of films and fibers from processing the isotropic anion solutions are also described. © 1990, American Chemical Society. All rights reserved.