Characterization of plasma-treated poly (hydroxybutyrate) membrane surfaces by ESCA and contact angle measurements

Poly (hydroxybutyrate) membranes were used as substrates for cold plasma treatment with perfluorohexane. By varying a gas mixture of perfluorohexane and hydrogen, surface coatings of different hydrophobicity were obtained. In addition, inorganic glass slides were treated correspondingly. The plasma-treated samples were analyzed by ESCA with respect to the surface composition and by contact angle measurements with respect to the surface free energy. Atomic structures and surface energies of the deposited layers on the polymer substrates were compared to those on inorganic substrates. In both cases a strong correlation was found between the fluorine/carbon ratio as well as the oxygen/carbon ratio and the surface free energy. Furthermore, the plasma-treated membranes were investigated and characterized by their changed permeation properties in order to identify the influence of the surface coatings on the bulk properties. Up to a coating density of 50–100 γ/cm2 the filtration properties of the treated membranes remained unaffected.