Synchrotron-based X-ray photoemission electron microscopy (X-PEEM) and atomic force microscopy (AFM) were used to characterize the composition and surface morphology of thin films of a polystyrene-poly(ethylene oxide) blend (PS-PEO), spun cast from dichloromethane at various mass ratios and polymer concentrations. X-PEEM reveals incomplete segregation with ∼30% of PS in the PEO region and vice versa. Protein (human serum albumin) adsorption studies show that this partial phase separation leads to greater protein repellency in the PS region, whereas more protein is detected in the PEO region compared to control samples.