POLYELECTROLYTE EFFECT IN PERFLUOROSULFONATED IONOMER SOLUTIONS

Ubbelohde viscosity measurements were performed on dilute solutions of perfluorosulfonated ionomers (PFSI) in various solvents exhibiting qu ite different dielectric constants. With aliphatic alcohols as solvent s an increase of the reduced viscosity with dilution is evident. This effect is analogous to the so-called 'polyelectrolyte effect' observed for highly charged ionic polymers in polar solvents. The polyelectrol yte effect increases with the dielectric constant for alcohols, is sim ilar in water and in methanol solutions, and disappears for high polar ity solvents. This evolution is discussed in terms of an increase of t he electrostatic persistence length. The viscosimetric behaviour of PF SI solutions is shown to fit well with the Liberti-Stivala equation.