We propose to study the density profiles of the non-fouling poly[N-(2-hydroxypropyl) methacrylamide] (poly(HPMA)) and antifouling poly[oligo(ethylene glycol)methyl ether methacrylate] (poly(MeOEGMA)) brushes at the solid-liquid interface by neutron reflectivity. The solvent-swollen brushes will be measured before and after contact with fibrinogen solution and whole blood plasma, at 25 and 37ºC at different contrast. Studies the brush profiles at different temperature will determine the importance of entropy on the resistance to fouling, while assessing the profiles after protein adsorption will aid at assessing whether fouling leads to changes in the conformation of the brush with a concomitant entropic penalty. The differences between the molecular conformations of the chains between poly(HPMA) and poly(MeOEGMA) brushes will help us to identify the key parameters rendering a surface non-fouling. Thus the obtained results will enable us to design synthetic protocols for surface modifications with predictable and tailor-made properties.