The structure of organosilicon plasma-polymerized coatings on metal substrates

The structure of coatings formed by the low pressure plasma-polymerization of hexamethyldisiloxane has been studied by FTIR and XPS techniques. The coatings were performed in two pressure regions: 0.63–0.88 and 0.36–0.44 torr. At both pressures much of the structure of the monomer appeared to be maintained. Coatings deposited at the higher pressure showed the expected increase in abstraction of methyl groups and formation of Si  O  Si crosslinks with increasing discharge power. The lower pressure coatings showed a markedly more diverse pattern of peaks associated with Si  O bonds. The spectra of the moncmer, hexamethyldisiloxane, and of a highly crosslinked silicone resin were examined in order to clarify the way in which FTIR spectra varied during the polymerization and crosslinking processes. The different structures observed emphasize a considerable potential for tailoring structure by varying deposition conditions.