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The stability of plasma-polymerized allylamine films with autoclaving sterilization cycles was investigated. Polymerized films were deposited under pulsed plasma conditions using two different duty cycles to provide surfaces having different initial amino group concentrations. The film properties were analyzed by XPS and water contact angle measurements before and after autoclaving. The reactions of these surfaces with trifluoroacetic anhydride provided quantitation of the amino surface concentrations before and after autoclaving. In general, the plasma-polymerized films exhibit good stability vis à vis the autoclaving process, with relatively high retention of the surface amino groups. The results of this work are of specific value with respect to tissue culture studies in which surface modifications involving the introduction of amino groups have been shown to have high efficacy in promoting cell growth. The results obtained suggest that the simple one-step plasma treatment process is a viable alternative to the more cumbersome surface modification procedures currently employed to introduce amino groups in these tissue culture studies.

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A variable-duty cycle-pulsed radio frequency discharge is shown to provide film chemistry control during plasma polymerization of acryloyl chloride. A nonlinear dependence is observed between the percent retention of acid chloride groups in the deposited films and the average power input during plasma polymerization. Significant C(O)Cl group retention is observed only under conditions of exceptionally low power input, as made available in the pulsed experiments. Additionally, relatively large scale systematic changes in surface morphology and film formation rates are observed with sequential variations in the plasma duty cycle employed during film formation. Specifically, film surface roughness decreases and the film thickness per joule of input energy increases as the plasma duty cycles employed are decreased. The plasma-generated films were employed in subsequent chemical reactions to attach target molecules to the substrate surfaces via facile reactions with the surface acid chloride groups. This concept is illustrated in the present paper with reactions of 1,1,1-trifluoroethanol and allylamine with the plasma-modified surfaces. The results obtained are supportive of the use of the ultralow-energy pulsed plasma technique to introduce reactive surface groups, followed by subsequent covalent coupling of target molecules, as a viable new route to molecular tailoring of surfaces.

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