Nature of dangling-bond sites in native plasma-polymerized films of unsaturated hydrocarbons, and electron paramagnetic resonance kinetics on heat treatment of the films

Abstract

We describe the electron paramagnetic resonance (EPR) study of dangling-bond sites (DBS) of plasma-polymerized films prepared from three unsaturated hydrocarbons, phenylacetylene, styrene and hex-3-yne. It has been shown that all the EPR spectra of DBS in such native films (before exposure to air) are much more intense than those after exposure to air. The DBS are quite stable at room temperature under anaerobic conditions, but their number begins to decrease towards a limiting value on heat treatment. However, when exposed to air the DBS decay rather rapidly; this decay tends to level off, indicating that there exist two different types of DBS, reactive and non-reactive. We discuss the difference in the nature of dissipation of DBS between oxidative and non-oxidative conditions.We also present the EPR spectral interpretations of the DBS and the reactions of several plasma-polymerized films previously reported.