Ionic poly (p-phenylene terephthalamide)s: Preparation and characterization

The preparation and characterization of two types of ionic poly(P-phenylene terephthalamide) (PPTA) is described. A sufficient number of ionic groups were added to render modified PPTA soluble in dimethylsulfoxide (DMSO). In one type, a hydrogen atom of the amide group was replaced by an ionic propa nesulfonate group. In the other type, one of the hydrogen atoms on the phen ylene ring was replaced by an ionic sulfonate group. The ionic PPTAs in DMS O showed an upturn in viscosity at very low concentrations that was charact eristic of the polyelectrolyte behavior. Fourier transform infrared spectra of these samples were also studied. When the ionic group was attached at t he end of the short propane side chain, the intensity of both the free and hydrogen-bonded N-H stretching mode was reduced compared with that of PPTA. Depending on the location of the ionic group, there were some changes in t he intensity and wave number of the asymmetric and symmetric vibrations of the ionic SO3- group and the stretching mode of the carbonyl group. In both ionic PPTAs, there was an upward shift in the frequency of the symmetric v ibrations of the sulfonate ion when the counterion, having been monovalent, became divalent. (C) 2001 John Wiley & Sons, Inc.