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Self-assembled Nafion films of varyingthickness were generatedon SiO2terminatedsilicon wafer by immersion in Nafion dispersions of different concentrations.The impact of solvent/dispersion media was probed by preparing filmsfrom two different types of Nafion dispersionsIPA-diluteddispersion and Nafion-in-water dispersion. The thickness of filmswas ascertained by three different techniques: variable angle spectroscopicellipsometry (VASE), atomic force microscopy (AFM), and X-ray photoelectronspectroscopy (XPS). The three techniques yielded consistent nominalthicknesses of 4, 10, 30, 55, 75, 110, 160, and 300 nm for films self-assembledfrom IPA-diluted Nafion dispersions of concentrations 0.1, 0.25, 0.5,1.0, 1.5, 2.0, 3.0, and 5.0 wt %, respectively. Films generated from0.25–5.0 wt % Nafion-in-water dispersions generated comparablethicknesses. An interesting finding of our work is the observationof bimodal surface wettability, investigated by water contact angle.The sub-55 nm films were found to exhibit hydrophilic surface whereasthe thicker films showed hydrophobic surface similar to those reportedfor Nafion membranes. Employing XDLVO theory, surface energies ofthe hydrophobic, 160 nm film was found to be similar to that reportedfor Nafion membrane whereas those for the hydrophilic 4 nm film yieldedhigh electron-accepting/proton-donating parameters resulting in anenhanced surface polarity. It can be concluded that the structureand properties of the ultrathin (<55 nm) Nafion films are distinctfrom those of the thicker (but still submicrometer) films, which arelikely similar to those of the well-studied Nafion membranes. No significanteffect of dispersion type was observed for 10–300 nm thickfilms. [ABSTRACT FROM AUTHOR]