Plasma polymerization of some simple saturated hydrocarbons

Methane, ethane, propane, and n-butane were polymerized in a plasma created by a radio-frequency glow discharge. It was found that the kinetics of polymer deposition were similar for all monomers but methane. It is suggested that the deviation from "normal" behavior of methane may be due to the difference in mechanism of formation of reaction intermediates. The "characteristic map" for the plasma polymerization of ethane was determined. It was shown that, in addition to transparent films, powders may be formed at low pressures and low monomer flow rates and unstable discharges at high pressures and low flow rates. With increasing power input, the unstable regions are decreased while the powdery regions are increased. The rates of polymer deposition were found to depend on pressure, flow rate, and power. An empirical equation is proposed that relates the rates of deposition for ethane, propane, and n-butane to these parameters.