Electrochemical study of the interfacial behavior of cationic polyelectrolytes and their complexation with monovalent anionic surfactants

► The interactions of polymers SC230 and SC240 with perfluorodecanate acid and perfluorooctanoate surfactants are studied. ► The effect of molecular weight of the polymer and chain length of the surfactant on the binding isotherms is investigated. ► It is concluded that the overall constant and cooperative binding process increase with the molecular weight of polymer. ► It is also found that the intrinsic constant, K0, increases with the anion chain length. ► The surfactant binding to the polymer is associated with electrostatic interactions and with hydrophobic interactions. The complexation of two hydroxyethylcellulose, of different molecular weights, SC230 and SC240, with the anionic surfactants perfluorodecanoic acid, PFDA, and perfluorooctanoic acid, PFOA, has been studied. For this purpose, the anions transfer current across a water/1,2-dichloroethane interface was employed to quantify PFDA and PFOA concentration in the absence or in the presence of the polyelectrolyte. When polymers were added in increasing amounts to solutions containing PFDA or PFOA, a gradual decrease in current values was observed, evincing the binding of the anions to the polymer. Peak Current values for the transfer, were used for the drawing up the binding isotherms, which were fitted by Satake and Yang theory. Cooperative binding was observed, but all fluorinated acids gave a similar cooperativity parameter, and it was found that both the overall constant as well as the cooperative binding process, increases with the molecular weight of the polymer.