Surface immobilization of poly(ethylene oxide): Structure and properties

We covalently immobilized poly(ethylene oxide) (PEO) chains onto a fluorinated ethylene propylene copolymer (FEP) surface. On the FEP surface, aldehyde groups were first deposited by plasma polymerization of acetaldehyde or acrolein. Then, amino-PEO chains were immobilized through Schiff base formation, which was followed by reduction stabilization with sodium cyanoborohydride. The PEO-grafted polymer surfaces thus prepared were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy, contact-angle measurements, and protein adsorption. The dramatic increase in the CO intensity of the high-resolution XPS C 1s spectrum, together with an overall increase in oxygen content, indicated the successful attachment of PEO chains onto the acetaldehyde plasma surfaces. The amount of grafted PEO chains depended on the superfacial density of the plasma-generated aldehyde groups. The grafted monoamino-PEO chains formed a brushlike structure on the polymer surface, whereas the bisamino-PEO chains predominately adopted a looplike conformation. The PEO surface had a regular morphology with greater roughness than the aldehyde surface underneath. Surface hydrophilicity increased with the grafting of PEO. Also, the bisamino-PEO-grafted surface had slightly higher surface hydrophilicity than its monoamino-PEO counterpart. These PEO coatings reduced fibrinogen adsorption by 43% compared with the substrate FEP surface.