Mass transport in Triton X series nonionic surfactant solutions: a new approach to solute-solvent interactions

Abstract

Densities, viscosities and tracer diffusion coefficients for solutions of the nonionic surfactants Triton X-45, X-114, X-100 and X-102 in water (except for Triton X-45) and methanol, and for Triton X-100 in three water-methanol mixtures have been measured at 298.15 K and 308.15 K. The activation energy for viscous flow and the contributions to it from solute and solvent have been calculated. Comparison of the Gibbs energies of these systems shows the roles of polyoxyethylene chains of Triton X molecules in the interactions between solute and solvent, and also the effects of solvents on the inter-actions for different solutes. The viscosityB coefficients are positive for all of the surfactant solutions, and the temperature coefficients ofB are negative. In the non-micellar solutions in methanol, values ofB are small and the temperature coefficient ofB is nearly zero. In water-methanol mixtures the critical micelle concentration becomes larger as the methanol content increases up to 40% w/w; micelles are not formed at higher methanol concentrations. TheB coefficient decreases with increasing proportion of methanol in the solvent, and the temperature coefficient ofB changes from a fairly large positive value at low methanol contents to a small negative value at 80% w/w methanol.