SURFACE MODIFICATION AND FUNCTIONALIZATION OF POLYTETRAFLUOROETHYLENEFILMS

Argon plasma-pretreated polytetrafluoroethylene (PTFE) films were subj ected to further surface modification by near-UV light-induced graft c opolymerization with acrylic acid (AAc), sodium salt of styrenesulfoni c acid (NaSS), and N,N-dimethylacrylamide (DMAA). The surface composit ions and microstructures of the modified films were characterized by a ngle-resolved X-ray photoelectron spectroscopy (XPS). A stratified sur face microstructure with a significantly higher substrate-to-graft cha in ratio in the top surface layer than in the subsurface layer was alw ays obtained for PTFE surface with a substantial amount of the hydroph ilic graft. The stratified surface microstructure was consistent with the observed hysteresis in advancing and receding water contact angles . The graft yield increased with Ar plasma pretreatment time and monom er concentration. Covalent immobilization of trypsin on the AAc polyme r-grafted PTFE films was facilitated by water-soluble carbodiimide(WSC ). The effective enzyme activities increased initially with increasing surface concentration of the grafted AAc polymer but became saturated at a moderate AAc polymer concentration. The immobilized enzyme could still retain close to 30% of its original activity. Solution-coating of the polymeric acid-modified PTFE films with the emeraldine (EM) bas e of polyaniline readily resulted in an interfacial charge transfer in teraction and a semiconductive PTFE surface.