A structural study of a polymer-surfactant system in dilute and entangled regime: Effect of high concentrations of surfactant and polymer molecular weight

Ahmed El Aferni (1) , Moez Guettari (1) , Marwa Kamli (1) , Tahar Tajouri (1) , Alain Ponton (2)

1 Université de Tunis
2 MSC - Matière et Systèmes Complexes

In the polymer-surfactant system, increasing the concentration of surfactant leads to structural changes in surfactant micelles. This is expected to influence the polymer conformation in the dilute regime where polymer chains are singles and in the entangled regime where the polymer system is described by the blob concept. In this report, the effect of large Sodium bis(2-ethylhexyl) sulfosuccinate (AOT), surfactant concentrations on the conformation of two polyvinylpyrrolidone (PVP) molecular weight (M w ¼ 55000 g/ mol and M w ¼ 360000 g/mol) was discussed. In the first part, in the dilute regime, C PVP 3C*where polymer chains are considered isolated, the determination of PVP (M w ¼ 55000 g/mol and M w ¼ 360000 g/mol) intrinsic viscosity ½h showed a coil to globule transition with the increase of temperature. Electrical conductivity measurements have shown the morphological transition (sphere-cylinder) of surfactant micelles with the increase of surfactant concentrations. The addition of AOT wormlike micelles revealed the expansion of PVP chains for the two molecular weight. In the second part, in PVP entangled regime,C PVP x16C* where overlapped polymer chains form molecular blobs, the addition of AOT wormlike micelles to PVP solutions doesn't affect the Newtonian behavior of PVP (M w ¼ 55000) and the pseudo-plastic behavior of PVP (M w ¼ 360000 g/mol). However, AOT surfactant reinforces significantly the dynamic viscosity of PVP,h for the two molecular weight. By fitting the PVP viscosity-temperature dependence with Fulcher-Tammann-Vogel law, the results showed that the more the surfactant is added, the stronger the PVP solution becomes, which proves that AOT cylindrical (wormlike) micelles presence enhances the solid character of PVP solutions.

Mots clés: Surfactant; Conductivity; Polymer; Pseudo-plastic behavior; Viscosity; Newtonian behavior

Domaines: Matière Molle [cond-mat.soft]; Polymères

Ahmed El Aferni, Moez Guettari, Marwa Kamli, Tahar Tajouri, Alain Ponton. A structural study of a polymer-surfactant system in dilute and entangled regime: Effect of high concentrations of surfactant and polymer molecular weight. Journal of Molecular Structure, 2020, 1199, pp.127052. ⟨10.1016/j.molstruc.2019.127052⟩. ⟨hal-02376443⟩