We propose to make neutron reflectivity measurements of hydrophillic polymers covalently attached, via thiol chemistry, to the gold-water interface. In particular, we will measure 10k and 20k end-attached poly(ethylene glycol) in an attempt to resolve some puzzling SANS and Surface Force Apparatus data that we have obtained from the 20k PEG attached to gold nanoparticles and a flat gold surface, respectively. The reflectivity measurements will enable us to determine if the non-uniform density profile measured in SANS is a consequence of interfacial curvature or a signature of the 2-phase brush predicted for PEG at high grafting density. We also plan to measure the same poly(hydroxy propyl methacrylamide) polymers for which we have measured SANS data when they are attached to virus particles used in Gene Therapy. The simpler interfacial geometry will help us interpret the virus SANS data.