Collective polyelectrolyte diffusion as a function of counterion size and dielectric constant

Abstract

We report studies of the effect of counterions on the properties of solutions of a strong polyelectrolyte for a wide range of solvent dielectric constant. For this purpose we investigated the dynamic properties of polystyrene sulfonate in N-methylformamide whose dielectric constant changes significantly with temperature. By means of dynamic light scattering and NMR spectroscopy, polymers of different molecular weights and various counterions were investigated, including large phosphazene counterions P1, P2 and P4 measured for the first time. It was found that the order of counterion binding of ionomers in the solvent changed with an increase of dielectric constant. The order for low dielectric constant (high temperature) was Na < Rb < Cs < P1 < P2 < P4, whereas for a solvent with high dielectric constant no influence of counterion nature was observed. The solvation-desolvation effect together with electrostatic interactions are responsible for the observed phenomenon. © 2012 Society of Chemical Industry.