This research is intended to measure the segment adsorption profile for a polymer physadsorbed to an interface from dilute solution. It will concentrate on the most simple case, that of a neutral homopolymer adsorbed to a neutral, smooth surface. This is idealized in the laboratory by the study of polymer adsorption from a dilute solution to the solution/air interface. The methods to be employed for the study are: X-ray Evanescent Wave Induced Fluorescence (XEWIF) and surface tensiometry on polymer solutions; These techniques measure the profile at the level of the segment size and the macroscopic (thermodynamic) scale. The studies will use fractionated poly(dimethylsiloxane) and measure its adsorption from solutions in toluene (good solvent). These experiments are intended to test the limits of mean-field theories and demonstrate the relative importance of fluctuations on the final density profile. This research initiation grant will test experimentally various theories of polymer adsorption, which are important in adhesion, coatings, and other applications.
