Oxidative graft polymerization of aniline on PTFE films modified by surface hydroxylation and silanization

Chemical modification of argon plasma-pretreated poly(tetrafluoroethylene) (PTFE) films by UV-induced graft copolymerization with 2-hydroxyethyl methacrylate (HEMA), followed by silanization with (p-aminophenyl)trimethoxysilane (APTS), and finally oxidative graft polymerization of aniline had been carried out to render the PTFE surfaces electrically conductive. The chemical composition of the PTFE surface after each step of surface modification was analyzed by X-ray photoelectron spectroscopy (XPS). The graft concentration of the HEMA polymer and the aniline polymer increased with increasing concentration of the respective monomer used for graft polymerization. The extent of APTS chemisorption increased with the graft concentration of the HEMA polymer, as well as the concentration of the APTS solution. A high extent of APTS chemisorption, in turn, led to a high graft concentration of the aniline polymer and thus a low surface resistance of the resulting PTFE film upon acid treatment (reprotonation) of the grafted aniline polymer. The grafted aniline polymer exhibited similar intrinsic oxidation states and reprotonation-deprotonation behavior as those of the aniline homopolymer. The grafted aniline polymer was found to be more effectively protonated by 10-camphorsulfonic acid (CSA) than by HClO4. The optimum surface resistance of the aniline polymer-grafted PTFE film was on the order of 10(3) Omega/sq.