Polyelectrolyte-surfactant complexes: an aqueous titration method to modelion-pairing within polymeric membranes of polyion-sensitive electrodes

A model for estimating the degree of cooperative ion-pairing that occurs be tween polyions and lipophilic ion-exchangers doped into the organic polymer membranes of polyion-sensitive electrodes has:been developed. The binding of several polyanionic (e.g., heparins, carrageenans, polyphosphates, and p olyglutamates) and polycationic species (e.g., protamine, polyarginine, and polylysines) with water soluble surfactants, quaternary ammonium and alkyl - and alkylbenzene sulfonates, respectively, which are structurally analogo us to the ion-exchangers, is monitored in aqueous solutions with surfactant -selective electrodes. Analysis of the binding data reveals that the polyio n structure, including polyion molecular weight, lipophilicity, and charge density, has a significant impact on the observed binding affinities, as do es the surfactant structure. It is also shown that the measured aqueous pha se binding affinities have a strong linear correlation with the equilibrium EMF changes observed with the respective polyion-sensitive electrodes, con firming the validity of using an aqueous system to model the binding behavi or of ion-exchangers with polyions within the organic polymer membranes of polyion-sensitive electrodes. (C)2000 Elsevier Science B.V. All rights rese rved.