Surface modification of poly(tetrafluoroethylene) films via grafting of poly(ethylene glycol) for reduction in protein adsorption

Poly(tetrafluoroethylene) (PTFE) films with surface grafted poly(ethylene glycol) (PEG) chains were prepared by two methods: (1) UV-induced graft copolymerization of methoxy poly(ethylene glycol) monomethacrylate (PEGMA) onto the plasma-pretreated PTFE films; and (2) coupling of the hydroxyl groups of PEG via ester linkages with the carbonyl chloride groups which were introduced onto the acrylic acid (AAc) graft-copolymerized PTFE surface through reaction with thionyl chloride (SOCl2). The UV-induced graft copolymerization of PEGMA onto the plasma-pretreated PTFE film was explored with different macromonomer concentrations and different UV graft copolymerization time, The coupling reaction, on the other hand, was explored with PEG of different molecular weights. The surface microstructures and compositions of the PEG-modified PTFE films from both processes were characterized by contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) measurements. In general, higher macromonomer concentration and longer UV graft copolymerization time led to a higher graft yield for the UV-induced graft copolymerization with PEGMA. Contact angle measurements revealed that the hydrophilicity of the PTFE film surface was greatly enhanced by the grafting of the PEG chains. The PTFE surface with a high density of grafted PEG was very effective in preventing bovine serum albumin adsorption.