A method to modify mica chemically by means of a plasma discharge in water vapour, to form reactive silanol groups, followed by silyation with isocyanatopropyldimethylchlorosilane has been developed. The introduction of isocyanatopropyl moieties on the surface enables the performance of a wide range of organic derivatization reactions. As examples, amino- and ethylene oxide-functional surfaces have been prepared. The surface film compositions have been quantitatively studied by ESCA. The interaction force in water between poly (ethylene oxide) layers covalently attached to mica, as measured in a surface force apparatus, was repulsive at separations less than 20-30 nm.