Properties of mixed aqueous solutions of perfluorooctanoate with poly(N-vinylpyrrolidone)

Aqueous mixtures of ammonium perfluorooctanoate (C8FN) and poly(N-vinyl-pyrrolidone) (PVP) were characterized by measuring the surface tension, conductivity and solubilization. Sodium perfluorooctanoate was also used for comparison. The critical micelle concentration (c. m. c.) of C8FN was found to be 30 mmol L(-1). The dependence of the surface tension on the surfactant concentration could be successfully described by the surface condensation based on the Langmuir-type adsorption. The cross-sectional molecular area of the C8FN oriented perpendicular on the surface is estimated at 19.8 Angstrom(2). The addition of PVP increases the molecular area, suggesting an interaction between C8FN and PVP on the surface. The solubilization of p-aminoazobenzene (PAAB) in these systems shows a synergetic effect in the low-concentration range of C8FN and PVP. Changes in the absorption spectra of PAAB indicated the interaction between C8FN and PVP.