POLYMER-FILMS WITH TUNABLE SURFACE-PROPERTIES - SEPARATION OF AN OIL-IN-WATER EMULSION AT POLY(3-METHYLTHIOPHENE)

We describe here the effect of an oil-in-water emulsion on the cyclic voltammetry of a redox probe at a platinum electrode coated with poly( 3-methylthiophene), PMeT, a material for which wetting properties can be tuned by controlling its oxidation (charging) level. When a water s oluble redox probe, such as potassium ferrocyanide or hexaammineruthen ium(III) chloride, is mixed in an oil-in-water emulsion, the current r esponse of the probe at Pt/PMeT decreases to less than 10%, consistent with adsorption of the disperse phase (oil + surfactant) at the polym er. On switching the partly blocked PMeT to its oxidized state, this p olymer turns hydrophilic, decreasing the hydrophobic interaction betwe en the polymer and the adsorbed oil particles. Removal of oil from the film is facilitated by electrostatic repulsion between the charged fi lm and the surfactant bound to the oil phase, as indicated by the reap pearance of the characteristic current signal at Pt/PMeT in an aqueous solution of the probe.