FRG: X-Ray Scattering Studies of Structure and Dynamics of Polymer Interfaces

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This is a Focused Research Group award between the University of California in San Diego, Northern Illinois University, and Yale University. Its aim is to carry out detailed structural and dynamical studies of polymer films, using the non-invasive proves of x-ray and neutron scattering at national synchrotron radiation and neutron scattering facilities, in order to achieve a better scientific understanding at the microscopic level of the static and dynamic behavior of macromolecules at solid/liquid interfaces and at free (liquid/vapor) surfaces in the fluid state and around the glass transition. This scientific understanding is needed because at present there is a considerable divergence of results from experiments and also of theoretical views regarding the nature of the fluctuations at polymeric surfaces and of the glass transition in thin polymer films. The roles of confinement (e.g. when the film thickness is comparable to the radius of gyration of the polymer chains) and of the polymer-substrate interactions need to be elucidated in more detail to achieve such an understanding. The techniques to be brought to bear on these problems include x-ray and neutron reflectivity, diffuse x-ray scattering, small-angle neutron scattering and x-ray photon correlation spectroscopy.The scientific interest driving this project stems from our present limited knowledge of how the conformation and mobility of polymer molecules are affected by confinement to a thin film and by interactions with the substrate and how these materials transform into the glassy state. It's technological importance is related to the important role played by polymer films in industry and technology in the form of coatings, adhesives, filters for chemical separations, packaging materials, lithographic masks for microelectronic devices, etc. Further, it will provide an opportunity for students and postdoctoral researchers at three different educational institutions to be trained in this important area of materials science and in the use of advanced research methods utilizing the nation's premier national facilities for research using synchrotron x-ray and neutron beams.