The sparing solubility of a rigid aromatic polyamide, poly(p- phenylene terephthalamide), PPTA, can be improved by introducing functional groups to the polymer, for example through the attachment of the sulfonic acid group (or its alkaline salt) to the aromatic ring, or by N-substitution with aligo (oxyethylene). The lithium or sodium salt of the sulfonic acid substituted polyamide, PPTS, form dilute aqueous gels which are birefringent and exhibit morphologies characteristic of nematic liquid crystalline structures. The order-disorder transition in these rigid polyelectrolyte gels will be studied by monitoring the evolution of the aggregated structures by light-scattering measurements and by microscopy using digital image analysis. These investigations will be supplemented by NMR experiments to detect changes in the relaxation rates of the polymer as the solution is cooled (or the gel is Heated) through the transition region. The enthalpy change associated with the transition will also be determined. The response of the rigid polyelectrolyte gels to electric stimulation is the second topic of this study, because the mechanochemical and chemical valve actions produced by electric stimulus find analogies in biological responses. It is also planned to study the miscibility of PPTS or its salts with flexible polymers. Poly(oxyethylene) PEO is a particularly interesting candidate because the Li-PPTS/PEO/LiClO4 system shows sufficiently high ion conductivity to warrant a systematic study. PPTA grafted at the N-position with oligo (oxyethylene) will be blended with PEO, poly(methyl methacrylate) or poly(acrylic acid). Since it is known that PEO is miscible with PMMA and forms complexes with PAA, it is likely that the PPTA-g-PEO polymer can be dispersed on a molecular level in PEO, PPMA, or PAA. Aside from using the graft copolymer to demonstrate the feasibility of this approach to molecular composites, the copolymer-PEO system will be evaluated as a potential ion conducting material. This research involves the study of novel solutions, gels, and polymer mixtures of potential interest as biomolecular materials and ionic conductors.
