Plasma assisted immobilization of poly(ethylene oxide) onto fluorocarbon surfaces

Different plasma-assisted procedures were compared with respect to the immobilization of poly(ethylene oxide) (PEO) and poly(ethylene-block-propylene) triblock copolymers (PEO-PPO-PEO) on top of thin plasma-deposited fluorocarbon layers. The fluorocarbon substrate was used as a model system for the common poly(tetrafluoroethylene) as it provides several advantages to apply surface-selective analytical methods. The fixation of pre-adsorbed PEO-PPO-PEO by argon plasma treatments on the fluorocarbon surface was found to produce less homogeneous coatings probably due to the insufficient adsorption of the triblock-copolymers on the substrate. More effective PEO coverage of the fluorocarbon surface was achieved by O2-plasma initiated graft polymerization of PEO-dimethacrylate (Mw = 400 g/mol) and PEO-monoacrylate (Mw = 1000 g/mol) from solutions or melts. X-ray photoelectron spectroscopy (XPS) and contact angle measurements were utilized for a detailed study of the modified surfaces. The efficiency of PEO-coatings with respect to the reduction of protein adsorption onto the hydrophobic fluorocarbon layer was demonstrated with the example of the adsorption of fibrinogen. The adsorbed amount of this protein was determined based on spectroscopic ellipsometry.