SURFACE MODIFICATION AND FUNCTIONALIZATION OF POLYTETRAFLUOROETHYLENEFILMS VIA GRAFT-COPOLYMERIZATION

Argon plasma pretreated polytetrafluoroethylene (PTFE) films were subj ected to further surface modification by near-UV light induced graft c opolymerization 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 m ethacrylate (GMA). The surface composition and microstructure of the m odified films were characterized by angle-resolved X-ray photo-electro n spectroscopy. A stratified surface microstructure with a significant ly 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 fil ms with molecularly redesigned surfaces are capable of exhibiting a nu mber of new functionalities. These new functionalities include (i) cov alent immobilization of an enzyme, such as trypsin (for AAc graft copo lymerized surface), (ii) change transfer included coating of an electr oactive polymer, such as polyaniline (for AAc and styrenesulfonic acid graft copolymerized surfaces), (iii) adhesive-free adhesion between t wo PTFE surfaces (for AAc, styrenesulfonic acid and DMAA graft copolym erized surfaces), and (iv) improved adhesive bonding via interfacial c rosslinking of the grafted chains (for GMA graft copolymerized surface s). (C) 1997 by John Wiley & Sons, Ltd.