Thermodynamic properties for aqueous solutions containing sodium pentane-1-sulfonate (C5SO3Na) in the absence and presence of poly(ethyleneglycol) (PEG) or poly(vinylpyrrolidone) (PVP) determined as a function of surfactant concentration from the density, sound velocity, viscosity, conductivity and vapor–liquid equilibria data, are reported here. Densities and sound velocities, allowing for the determination of apparent molar volumes and compressibilities, were measured at 288.15–313.15 K. Changes in the apparent molar properties upon micellization were derived using a pseudo-phase-transition approach and the infinite dilution apparent molar volumes and compressibilities of the monomer and micellar state of C5SO3Na in the investigated solutions were determined. The values of the infinite dilution apparent molar properties of micellar states of C5SO3Na in aqueous polymer solutions are larger than those in pure water. Vapor–liquid equilibrium data such as water activity, vapor pressure, osmotic coefficient, activity coefficient and Gibbs free energies were obtained through isopiestic method at 298.15 K. The variations of the critical micelle concentration (CMC) of C5SO3Na in water and in aqueous PEG and PVP solutions with temperature were obtained and a comparison between the CMC of C5SO3Na obtained from different thermodynamic properties was also made.
