Effect of Solvent Quality on the Behaviour of Highly Charged Polyelectrolytes

(Received 16 May 1995, received in final form 30 June 1995, accepted 24 July 1995)

Abstract
We show experimentally that the solutions properties of highly charged polyelectrolytes depend on the solvent quality for the backbone. Sulfonated Polystyrene, with hydrophobic backbone, and Poly(acrylamide- co-sodium-2-acrylamido-2-methylpropane sulfonate), with hydrophilic backbone, have been investigated by SAXS and fluorescence emission in a charge fraction range between 0.35 and 1, above the onset of Manning-Oosawa counterion condensation. The hydrophilic polyelectrolyte follows the prediction of the current models whereas the behaviour of polystyrene sulfonate cannot be reconciled with any existing model.

Résumé
Une étude par diffusion de RX aux petits angles et émission de fluorescence de solutions aqueuses de polystyrènes sulfonate de sodium (squelette hydrophobe) et de 2-acrylamido-2-méthyl-propane sulfonate de sodium (squelette hydrophile) a montré l'importance de la qualité du solvant sur la structure de ces solutions. La fraction de monomères chargés, entre 0,35 et 1, est supérieure au seuil de condensation de Manning-Oosawa pour les contre-ions. Le polyélectrolyte hydrophile suit qualitativement les modèles théoriques proposés, contrairement au polyélectrolyte hydrophobe dont le comportement ne peut être confronté aux prédictions théoriques.