Surface modification and functionalization of polytetrafluoroethylene films via graft copolymerization

Abstract

Argon plasma pretreated polytetrafluoroethylene (PTFE) films were subjected to further surface modification by near-UV light induced graft copolymerization with hydrophilic and epoxide-containing monomers. Thus, the functional monomers used include acrylic acid (AAc), sodium salt of styrenesulfonic acid, N,N-dimethylacrylamide (DMAA) and glycidyl methacrylate (GMA). The surface composition and microstructure of the modified films were characterized by angle-resolved X-ray photoelectron spectroscopy. A stratified surface microstructure with a significantly higher substrate-to-graft chain ratio in the top surface layer than in the subsurface layer is always obtained for the PTFE surface with a substantial amount of graft. In all cases, the graft yield increases with plasma pretreatment time and monomer concentration. The PTFE films with molecularly redesigned surfaces are capable of exhibiting a number of new functionalities. These new functionalities include (i) covalent immobilization of an enzyme, such as trypsin (for AAc graft copolymerized surface), (ii) charge transfer induced coating of an electroactive polymer, such as polyaniline (for AAc and styrenesulfonic acid graft copolymerized surfaces), (iii) adhesive-free adhesion between two PTFE surfaces (for AAc, styrenesulfonic acid and DMAA graft copolymerized surfaces), and (iv) improved adhesive bonding via interfacial crosslinking of the grafted chains (for GMA graft copolymerized surfaces). © 1997 John Wiley & Sons, Ltd.