Plasma Polymerization of Ethylene and the Series of Fluoroethylenes: Plasma Effluent Mass Spectrometry and ESCA Studies

Abstract

The plasma polymerization of ethylene and the series of fluorinated ethylenes has been investigated in a capacitively coupled, low-pressure radio-frequency system. ESCA analysis of the polymer films allowed the relative concentrations of CF3, CF2, CF, and carbon not directly attached to fluorine to be determined. The structures and stoichiometries of the films were found to exhibit distinct trends depending on the injected material. The neutral species in the effluents of the plasmas were analyzed by mass spectrometry and this data coupled with the ESCA data allowed the primary precursors to polymerization to be identified. In going along the series from ethylene to tetrafluoroethylene the relative importance of acetylene in the plasma steadily decreases while that of difluoroacetylene increases. The relative importance of fluoroacetylene exhibits a maximum at the isomeric difluoroethylenes. Methylene plays an important role in the ethylene plasma while the relative importance of difluorocarbene increases along the series until for tetrafluoroethylene the plasma reactions are dominated by :CF2 and CF2CF2 itself. We believe that plasma polymerization proceeds via a plasma-induced mechanism involving the unchanged injected material and a second mechanism involving the initial formation of these other precursors in the plasma. © 1981, American Chemical Society. All rights reserved.