The conformation of biopolymers in solution and on surfaces, as well as changes in conformation caused by external stimuli or molecules which bind to the biopolymers, are central to the biological activity and function of the respective biopolymers. Our research addresses conformation, association and interactions in solution and on surfaces of blood proteins which are involved in haemostasis and thrombosis. This presentation will highlight results on interactions in aqueous solutions of fibrinogen with poly(ethylene glycol)-containing polymers that are known to prevent non-specific protein adsorption on surfaces. This information has been obtained by light and neutron scattering experiments. Be examining PEG homopolymers (of different molecular weights) and poly(ethylene glycol)-poly(propylene glycol) block copolymers, we can assess repulsive or attractive interactions and PEG polymer adsorption on / complexation with fibrinogen.