Nucleophilic Derivatization of Polyethylene Surfaces Treated in Ambient-Pressure N 2 –H 2 DBD Post Discharges

Chemical derivatization analysis of polyethylene surfaces plasma-treated in the afterglow regions of dielectric barrier discharges in mixtures of nitrogen and hydrogen was studied, using nucleophilic instead of electrophilic reagents which have commonly been used in studies of polymer surfaces exposed to discharges in nitrogen or nitrogen-containing gases. Vapors of strongly nucleophilic 2-mercaptoethanol and 4-(trifluoromethyl)-phenylhydrazine (TFMPH), respectively, were used for derivatization. XPS spectroscopy was subsequently applied in order to quantify the amount of sulfur and fluorine, respectively, introduced to the surface due to the presence of electrophilic moieties generated by the plasma treatment. Using FTIR-ATR spectroscopy following TFMPH derivatization, a quantitative determination of the hydrazone groups formed was possible, based on a comparison with spectra of a low-molecular weight model hydrazone. The results of these investigations confirm conclusions from earlier studies showing that the formation of electrophilic groups such as imines on polymers treated in afterglows of nitrogen–hydrogen DBDs must not be disregarded.