The adsorption of plasma proteins (fibrinogen and albumin) from buffer onto polystyrene-graft-(stearyl-poly(ethylene oxide)) (PS-g-SPEO) was investigated by radioiodine labeling of proteins using the iodine monochloride method. The molecular mobility of poly(ethylene oxide) grafts was determined by ESR spectroscopy, and the effects of PEO mobility on the ability of PS-g-SPEO to resist the non-specific protein adsorption have been studied. The non-specific adsorption of fibrinogen was found to decrease with increasing PEO mobility, whereas the interfacial energies lack significant correlation to the protein adsorption. The elastic restoring force seems much more important than hydrophobic interaction in PS-g-SPEO/protein interfaces. The high molecular mobility of PEO side chain is supposed to be the key effect on the protein-resistant properties of PS-g-SPEO. The protein adsorption results also reveal that the molecular mobility of PEO has a quite important role in developing albumin preferential materials. A high albumin preferential adsorption layer has been developed by immobilizing the stearyl end groups onto high mobile PEO chains. (C) 2000 Elsevier Science Ltd. All rights reserved.