Oligo(ethylene glycol) self-assembled monolayers (SAMs) effectively prevent the adsorption of proteins from biological media. Despite the importance of this effect for bio-technical applications, the molecular-level understanding of the mechanisms leading to protein resistance is limited. Various mechanisms have been proposed to explain the prevention of irreversible adsorption. However, the small length scales of the interactions make studies, especially in-situ, rather difficult. This proposal aims at obtaining high resolution structural information of the interfacial region at the SAM/protein solution interface with the aid of polarised neutron reflectivity using a magnetic reference layer.This will allow the determination of the protein density profile for different protein sizes and a study of the transition from a resistant to an adsorbing surface using temperature switchable SAMs.