Organosilicon plasma polymer and silicalike layers are deposited at different temperatures in a dielectric barrier discharge at atmospheric pressure operating in the Townsend regime. Final properties of these two kinds of layers can be finely tuned by the plasma process conditions. In particular, influence of deposition temperature is investigated when hexamethyldisiloxane based monolayers are deposited on poly(ethylene naphtalate) substrate. Coating chemical structure is tested by means of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Their thickness, topography, and mechanical properties are evaluated by ellipsometry, scanning electron microscopy observation of coatings cross sections, atomic force microscopy, and nanoscratch testing. Permeability of coated polymer is measured for transparent silicalike layers, and the effect of coating structure on the oxygen gas permeability is discussed. The deposition temperature of coatings at 90 °C provides a strong improvement in barrier property compared to room temperature deposition, thanks to a densification of the SiO₂ matrix and to a decrease in the silanol group content.

This paper aims at describing the synthesis of plasma polymer films by means of atmospheric filamentary plasma dielectric barrier discharge. This work highlights the fact that molecular structures of siloxane based plasma films can be tuned according to the so‐called Yasuda's parameter, which corresponds to the W/F ratios (W = power discharge; F = Monomer flow rate). Indeed, we showed that the plasma films exhibit a polydimethylsiloxane (PDMS) structure when W/F was low (i.e. when low plasma energy is applied), whereas SiOx structures were rather obtained when W/F is high (i.e. high plasma energy). These results were validated thanks to a wide set of analytical tools allowing to identify two domains where molecular structures of the plasma films swiftly progress from PDMS to SiOx according to W/F ratios.