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Title
| - Surface Modification and Functionalization ofPolytetrafluoroethylene Films
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Abstract
| - Argon plasma-pretreated polytetrafluoroethylene (PTFE)films were subjected to furthersurface modification by near-UV light-induced graft copolymerizationwith acrylic acid (AAc), sodiumsalt of styrenesulfonic acid (NaSS), andN,N-dimethylacrylamide (DMAA). The surfacecompositions andmicrostructures of the modified films were characterized byangle-resolved X-ray photoelectronspectroscopy (XPS). A stratified surface microstructure with asignificantly higher substrate-to-graftchain ratio in the top surface layer than in the subsurface layer wasalways obtained for PTFE surfacewith a substantial amount of the hydrophilic graft. The stratifiedsurface microstructure was consistentwith the observed hysteresis in advancing and receding water contactangles. The graft yield increasedwith Ar plasma pretreatment time and monomer concentration.Covalent immobilization of trypsin onthe AAc polymer-grafted PTFE films was facilitated by water-solublecarbodiimide (WSC). The effectiveenzyme activities increased initially with increasing surfaceconcentration of the grafted AAc polymerbut became saturated at a moderate AAc polymer concentration. Theimmobilized enzyme could stillretain close to 30% of its original activity. Solution-coating ofthe polymeric acid-modified PTFE filmswith the emeraldine (EM) base of polyaniline readily resulted in aninterfacial charge transfer interactionand a semiconductive PTFE surface.
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