Single-Coil to Aggregate Transition of Sulfonated Polystyrene Ionomers in Xylene Studied by Dynamic Light Scattering

A single-coil to aggregate transition in the zinc salts of sulfonated polystyrene ionomers in xylene was studied by dynamic light scattering. As the polymer concentration was increased in the dilute regime, the measured average diffusion coefficient of the polymer molecules decreased, and it was accompanied by a broadening in the distribution of the coefficient. Spectral analysis of the light scattering autocorrelation function revealed a clear transition from a single- to a dual-decay rate mode with increasing solute concentration, the faster being identified as the diffusion of isolated coils. Thus the slowing-down of the average diffusion with increasing polymer concentration was ascribed to the emergence of aggregates. The overall weight fraction of the aggregates, however, remained low.