Functionalization by Cold Plasmas of Polymer Model Surfaces (Hexatriacontane and Octadecyloctadecanoate) Studied by Contact Angle Measurements, XPS, and FTIR Spectroscopy

Surface functionalization by argon or oxygen RF plasmas (13.56 MHz) of polymer model compounds, namely hexatriacontane (C36H74) and octadecyloctadecanoate [OOD, CH3(CH2)16COO(CH2)17CH3, was studied using contact angle measurements, XPS, and FTIR-ATR. In order to gain a better insight into the plasma-surface interaction mechanisms, the effects of the main plasma parameters (treatment time, power, pressure, and flow rate) on functionalization were investigated. It was shown that an argon plasma is more efficient than an oxygen plasma and that the ester-containing model compound incorporated less oxygen than the paraffinic one. After 10 seconds of treatment, contact angle measurements showed that none of these plasma parameters affect in any way the properties of the uppermost surface layer; these depend only on the nature of the sample and on the gas used in the plasma. On the other hand, ESCA, which allows a 70-Å in-depth probing, reveals the influence of the plasma parameters on both types of samples. IR, which probes to a much greater depth, evidences an evolution only for treated OOD samples. Interpretations are proposed for the effect of the plasma parameters on functionalization.