Effect of Urea on the Interaction of Polyvinyl Alcohol with Sodium Dodecyl Sulfate

Abstract

The effect of urea on the interaction of polyvinyl alcohol (PVA) with sodium dodecyl sulfate (SDS) in aqueous solution was investigated by means of viscosity, electrophoresis, and dialysis equilibrium. In the absence of urea, the intrinsic viscosity [η], the electrophoretic mobility u, the number of effective charge Z (corresponding to the number of bound surfactant ion on PVA) of PVA-SDS complex, and the bound SDS on PVA changed depending on the SDS concentration (Cs) in solution and increased steeply from the vicinity of the first critical micelle concentration (cmc) of the surfactant. Then the first three reached maxima at the concentration corresponding to the second cmc. In the presence of urea, [η] Cs, uCs, ZCs curves and the bound SDS on PVA changed with the concentration of urea. At SDS concentrations higher than the first critical micelle concentration, the above three curves fell and the bound SDS decreased with increasing concentration of urea. These results suggest a release of the bound SDS from PVA and a contraction of the PVA-SDS complex molecule by the weakening of the electric repulsion between the surfactant ions bound on PVA.