The Dynamics of Organic Films on Different Time Scales

University Of Missouri-Columbia, Columbia MO

Investigators

Abstract

Non-technical Abstract This project focuses on films of alkanes [chemical formula CnH2n+2], flexible chain-like molecules that are of general interest in materials science as prototypes of more complex polymers used in coatings, adhesives, and electronic devices. Alkanes are also the principal constituents of commercial lubricants. A microscopic understanding of the structural and dynamical properties of alkane films could potentially lead to technological advances ranging from more durable polymer coatings to lubricants that reduce wear in automobile engines and in nanoscale devices such as computer hard drives. This project will utilize high-resolution scattering of neutrons and computer simulations as the principal techniques to determine the rates at which flexible alkane molecules change their shape and how these conformational changes affect the molecules' ability to stick to a solid surface. Experiments will be conducted on state-of-the-art neutron spectrometers at the Center for Neutron Research at the National Institute of Standards and Technology and at the newly constructed Spallation Neutron Source at Oak Ridge National Laboratory. The project includes structural studies utilizing Atomic Force Microscopy, synchrotron x-ray scattering at Argonne National Laboratory, and neutron diffraction at the University of Missouri Research Reactor. This research will provide training of undergraduate and graduate students in fundamental aspects of polymer science, preparing them for careers in industry and academia as well as at our expanding national facilities for neutron and x-ray scattering. Technical Abstract Proposal No.: DMR- 0705974 Proposal Title: The Dynamics of Organic Films on Different Time Scales PI/PD: Haskell Taub This project focuses on films of alkanes [CnH2n+2], flexible chain-like molecules that are of general interest in materials science as prototypes of more complex polymers used in coatings, adhesives, and electronic devices. Alkanes are also the principal constituents of commercial lubricants. A fundamental issue concerned with films of intermediate-length alkane molecules (15 < n < 50) is the effect that changes in molecular shape (conformation) induced by heating may have on binding of molecules to a solid surface and, at a macroscopic level, the wetting of the fluid film to a surface. These conformational changes are important for understanding such technologically important phenomena as the evaporation of thin lubricant films from the surfaces of magnetic storage disks, the desorption of alkanes from catalytic surfaces, and the lubricating characteristics of alkane films. This project will utilize quasielastic neutron scattering and molecular dynamics simulations as the principal techniques to investigate the molecular conformational changes that occur over a range of time scales (picoseconds to nanoseconds) in alkane films adsorbed on solid surfaces. Experiments will be conducted on state-of-the-art neutron spectrometers at the Center for Neutron Research at the National Institute of Standards and Technology and at the newly constructed Spallation Neutron Source at Oak Ridge National Laboratory. Since interpretation of the dynamical experiments requires knowledge of the film structure, the project includes structural studies utilizing Atomic Force Microscopy, synchrotron x-ray scattering at Argonne National Laboratory, and neutron diffraction at the University of Missouri Research Reactor. This research will provide training of undergraduate and graduate students in fundamental aspects of polymer science, preparing them for careers in industry and academia as well as at our expanding national facilities for neutron and x-ray scattering.