Rodlike Colloidal Structure of Short Pendant Chain Perfluorinated Ionomer Solutions

The colloidal structure of perfluorinated ionomer solutions in polar solvents which are not able to dissolve the neutral polymer analogue is confirmed studying short pendant chain perfluorosulfonated ionomer solutions by small-angle X-ray and neutron scattering. The analysis of the form factor obtained from the "dilute" solution spectra combined with the asymptotic behavior at large q values indicates the existence of rodlike shape aggregates. The radius is found to be 17 Å for aqueous solutions. The effects of the nature of the solvent and of the presence of added salt are studied. The origin of the scattering maximum is attributed to a local ordering between aggregates, and the value of the radius calculated from the peak position using space filling arguments compares well with other determinations. Finally, the study of the evolution of the reduced viscosity against the concentration shows evidence of a strong polyelectrolyte effect.