Membrane fouling phenomena, which can be certainly promoted by the adsorption of biomolecules such as proteins and polysaccharides, have been one of the major challenges in membrane separation. Surface modification has recently become a promising approach to suppressing such fouling. In this study, to conduct a computational design of an optimal surface modifier, a simple strategy has been applied, where the local affinities between an amino acid residue and a repeating unit of a candidate material are evaluated, by calculating free energy profiles for a residue approaching a repeating unit in explicit water molecules from a molecular dynamics simulation. We show that the predicted profiles for a 2-methoxyethylacrylate monomer have almost no energetically stable points. On the other hand, the profile for a conventional isophthalamide shows an energetically remarkable minimum. These results show the possibility for drastically simplifying the screening procedures of an optimal surface modifier.