Polymer Surface Treatment with SO2-Containing Plasmas

Polyethylene, poly(propylene), and polyester were treated with sulfur dioxide plasma and with plasmas using a mixture of SO2 with oxygen or with hydrogen. Depending on the process gas and the treatment conditions the functional groups formed by the plasma treatment can be sulfides or groups with highly oxidized sulfur such as sulfonic acid groups and sulfates. XPS and infrared reflection absorption spectroscopy (IRRAS) were used to identify the surface functional groups. The acidic groups (sulfonic acid, hydrogen sulfates) were quantified by fluorescence labeling with dansyl cadaverine. Values of up to 820 pmol · cm−2 were found. The acidic functional groups were also used as starting points for further functionalization of the surfaces. In the reaction with diamino ethane, primary amines were produced on the surface. Sulfur dioxide containing plasmas produce bright blue light and a high concentration (up to 820 pmol cm−2) of reactive functional groups. Depending on the composition of the process gas, functional groups are produced which can react with nucleophilic (e.g., amines) or with electrophilic (e.g., carboxylic acids) agents.