Structure of polyvinylpyrrolidone aqueous solution in semi-dilute regime: Roles of polymer-surfactant complexation

Abstract

The effect of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) addition on the structure of polyvinylpyrrolidone (PVP) aqueous solution, in dilute and semi-dilute regimes, has been investigated at 25 °C. The intrinsic viscosity, Huggins constant, Flory exponent and the Mark-Houwink-Sakurada coefficient were deduced by viscosimetry. The structure of PVP (MW = 40.000 g/mol) aqueous solution in semi-dilute regime was described according the blob model. The monomer size, the density of monomer, the correlation length and the number of monomer in each blob were determined. The PVP-AOT interaction in water was studied in dilute and semi-dilute concentration regime of the polymer by electrical conductivity. A complexation occurs between polymer and surfactant independently on the concentration regime, where the complex nature depends on surfactant concentration. The overlapping concentration of PVP-AOT aqueous solution increases with increasing AOT concentration from 0 to 0.6 g/dl. The Flory exponent decreases from 0.545 to 0.509 and the Mark-Houwink-Sakurada coefficient decreases from 0.636 to 0.528 g/dl. The effect of AOT complexation with PVP in water was also discussed according the blob model. At the overlapping concentration, the density of monomers and the correlation length decrease with increasing surfactant concentration. The density of monomers increases from its value at the overlapping concentration as the polymer concentration increases at the semi-dilute regime. However, the monomer size, the correlation length and the number of monomer in each blob decrease from their values at the overlapping concentration as the polymer concentration increases.