Surface molecular tailoring via pulsed plasma-generated acryloyl chloride polymers: Synthesis and reactivity

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)C1 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.