KINETICS OF COIL OVERLAP IN IONOMER BLENDS BY H-1-NMR IN DMSO-D6 .2. MECHANISTIC ASPECTS

H-1 nuclear magnetic resonance (NMR) studies were carried out on solut ions of blends of lightly sulfonated polystyrenes (PS-SSA; 5-15 mol % sulfonation) of molecular weight (MW) 12 000 and 100 000, with poly(me thyl methacrylate-co-4-vinylpyridine) (PMMA-4VP) copolymers (11 mol %) of MW congruent-to 100 000. The process of coil overlap was monitored as a function of time by the acquisition of proton spectra, which sho wed the gradual disappearance of the original methoxy signal and the a ppearance of a new signal originating from the shielded methoxy proton s. The contributions of the two species were separated using a deconvo lution program. To propose a complete model for the coil overlap pheno menon, parameters that can influence the kinetics of the process were studied. The parameters included the ion content and the MW of the PS- SSA, the temperature, and the total polymer concentration. The study o f these parameters showed that the overlap was occurring through a com plex mechanism. It was determined that the true order (n(c)) for the s hielding process was second-order, reflecting the early stages of the mixing process. At the stage at which a ''ladder''-like complex is pro duced, the experimental data can best be represented by a kinetic expr ession containing two opposing first-order reactions.