Surface modification of fluorine-containing polymers by atmospheric pressure plasma jet with negative substrate biasing

Fluoropolymers are difficult materials to modify the surfaces because of strong C-F bonds. In this study, the surface modification of fluoropolymer films such as polytetrafluoroethylene (PTFE) with amino groups was performed by using He/NH₃ gas mixture atmospheric pressure plasma jets with negatively-biased substrate. It is expected that the ion bombardment effect onto the polymer surface due to negative substrate bias will make dangling bonds over the polymer surface and eventually promote the surface modification. From XPS analysis, we confirmed the breaking C-F bonds and creating C-C, C=O or C-N bonds in C 1s spectrum and increasing nitrogen-containing functional groups in N 1s spectrum. Fluorescence patterns were observed on the amino group functionalized PTFE surface by using the fluorescent dyes selectively connecting with the amino groups. With a spectrophotometric method, the surface concentration of amino groups introduced onto the PTFE surface was evaluated to be roughly 3.86 nmol/cm².