Entropic Routes to Hydrophilic / Biocompatible Polymer Surfaces. D.G. Walton, P.P. Soo, A.M. Mayes, Department of Materials Science and Engineering, Massachusetts Institute of Technology, S.J. Sofia Allgor, J.T. Fujii, L.G. Griffith, Department of Chemical Engineering, Massachusetts Institute of Technology, J.F. Ankner, H. Kaiser, Research reactor Center, University of Missouri-Columbia, S.K. Satija, Reactor Radiation Division, National Institute for Standards and Technology -

Thin film blends of branched and linear polymers are studied by neutron reflectivity to examine the effect of branching on surface segregation. A branched additive consisting of poly(ethylene oxide) side chains distributed randomly along a methacrylate backbone is blended in various concentrations with a matrix of high molecular weight poly(methyl methacrylate). Results show a large surface coverage of the higher-energy branched additive, indicating that the segregation is entropically, rather than enthalpically, driven, providing a non-water-soluble and thermodynamically stable hydrophilic surface. The biocompatibility of this surface is also explored through protein adsorption and cell adhesion experiments.