Deposition of Water-Stable Coatings Containing Carboxylic Acid Groups by Atmospheric Pressure Cold Plasma Jet

Thin films containing carboxylic acid groups are deposited from mixtures of helium, acrylic acid, and ethylene using an atmospheric pressure cold plasma jet in dielectric barrier discharge (DBD) configuration. The influence of the feed gas composition on the properties of the deposits is investigated. As assessed by X-ray photoelectron spectroscopy (XPS), the oxygen atomic concentration of the coatings as well as the percentage of the XPS C1s component ascribed to carboxylic groups (i.e., COOH and COOR moieties) increase with the acrylic acid concentration in the feed gas. On the other hand, ethylene addition enhances the deposition rate, reduces the carboxylic groups content of the coatings, and significantly improves their chemical and morphological stability upon immersion in water for 72h. The surface concentration of COOH groups before and after immersion in water is determined by chemical derivatization in conjunction with XPS.