A new technique for elucidation of the surfactants' effect on the water uptake by Nafion membranes

A new technique for elucidation of the surfactants' effect on water uptake by Nafion membranes has been developed. It is based on piezoelectric technique, spectrophotometry, and contact angle measurements. The elaborated technique allows determination of the water uptake by a polymer membrane and monitoring of the change in the film surface properties after bringing the same sample in contact with water and the surfactant solutions. It has been shown that anionic surfactants (sodium dodecyl sulfate and dodecylbenzenesulfonic acid) do not affect water uptake by Nafion membranes, whereas cationic surfactant (dodecylpyridinium chloride) reduces the membrane water uptake by a factor of 1.6. The surface energy (γ_SV) of the Nafion membrane has been determined, and the effect of adsorption modification on its polar (γ^p_SV) and dispersion (γ^d_SV) components has been revealed.