HYDROPHOBIC RADIOFREQUENCY PLASMA-DEPOSITED POLYMER-FILMS - DIELECTRIC-PROPERTIES AND SURFACE FORCES

Advancing and receding contact angles for various liquids placed on th e surface of thin n-hexane plasma polymer films have confirmed that th e surface is hydrophobic; comparable to polyethylene. A waveguide tech nique has been employed to determine the refractive indices of the pla sma polymer films in the visible and near infrared regions of the diel ectric spectrum. Along with ESCA data that provide polymer group funct ionality, this information has been used to estimate the n-hexane plas ma polymer density and to construct a simple dielectric permeability f unction (epsilon(i xi), the dielectric constant at imaginary frequency i xi) for the polymer. The dielectric permeability function and Lifsh itz theory have been used to calculate the Hamaker function (including non-retarded Hamaker constants) which should characterise the van der Waals interaction in systems that contain n-hexane plasma polymers. T he atomic force microscope (AFM) has been employed to measure the forc e of interaction between n-hexane plasma polymer films deposited on mu scovite mica hat plates and either uncoated silicon nitride AFM tips o r n-hexane plasma polymer coated glass spheres. The force versus separ ation curves have been compared with DLVO theory. The homo-interaction between n-hexane plasma polymer coatings in water initially displays a long-range attraction additional to van der Waals interaction. There is evidence that after prolonged immersion in water the thin n-hexane plasma polymer films swell. (C) 1997 Elsevier Science B.V.