Abstract
The composition and the structure of plasma-polymerized tetrafluoroethylene (PPTFE) in thin film, which was formed in the glow region, were investigated by means of X-ray photoelectron spectroscopy (XPS). The ratio of fluorine to carbon (F/C) in the PPTFE was determined to be 1. 42 by use of intensities of the F18 and C18 spectra. The curve resolution of the broad signal for C18. resulted in five kinds of peaks with different C18, electron binding energies : 284. ± 0. 4, 287. 0± 0.3, 289. 0± 0.2, 291.5± 0.2, and 293.6± 0.1 eV. In order to assign the C18 spectra, the Cls energy shifts (ΔE (C18)) for the specified carbon atoms of several model compounds were estimated by using (i) an electrostatic potential model based on the CNDO/2 calculation of the atomic charges and (ii) an electronegativity parameter method. An empirical equation concerning the increment of C18 electron binding energy due to fluorine substitution was derived from the theoretical calculation. By reference to this empirical equation, it was confirmed that the PPTFE includes highly branched and cross-linked segments.
