BLOCK-COPOLYMER IONOMERS - SOLUTION BEHAVIOR OF LIGHTLY SULFONATED POLYSTYRENE-B-POLY(TERT-BUTYLSTYRENE) IN POLAR-SOLVENT

Light scattering experiments were performed to study the structure and dynamics of block copolymer ionomers in polar solvent. Two lightly su lfonated polystyrene-b-poly(tert-butylstyrene)copolymers in the sodium form with a sulfonation level of 5.8 and 12.0 mol % dissolved in N,N- dimethylacetamide were studied at 25, 45, and 60-degrees-C in the dilu te-solution regime. A polyelectrolyte-like solution behavior was obser ved. Due to the repulsive electrostatic interactions between like char ges, the scattered intensities monitored were greatly reduced as compa red with those of the unmodified diblock copolymer. In particular, a c haracteristic bimodal relaxation mode was observed on block ionomer so lutions in strong contrast to the single-exponential decay found for t he parent (neutral) copolymer solutions. Both the free-particle diffus ion coefficient and the macroscopic self-diffusion coefficient as a fu nction of temperature and concentration were determined and discussed. It seems that at 45 and 60-degrees-C charged monomolecular micelles a re formed, whereas charged polymolecular aggregates would exist at roo m temperature arising from the delicate balance between the aggregatio n tendency and the solvent affinity.