Development of Self-Healing Boundary Lubrication Films Using Polymeric Liquids Containing Ionic Functional Groups

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Development of Self-Healing Boundary Lubrication Films Using Polymeric Liquids Containing Ionic Functional GroupsPI: Seong H. KimDepartment of Chemical Engineering, The Pennsylvania State UniversityAbstractThe main focus of this research is to develop self-healing boundary lubricants suitable for microelectromechanical systems (MEMS). MEMS devices are widely utilized in miniature satellites, airflow control, sensors, actuators, accelerometers, gyroscopes, microwave switches, aircraft turbine engines, unmanned aerial vehicles, etc. Protecting MEMS devices against friction, wear, adhesion and other destructive phenomena that hinder performance and shorten operational life poses a significant challenge to militaries as well as commercial industries. The key for reliable boundary lubricant film is to control the interaction between the lubricant molecule and the substrate surface. Most of the boundary lubricants currently studied or employed in industries are attached to the substrate surface via chemical bonding. In this case, a strong binding of the lubricating layer can be achieved; but the lateral mobility needed for self healing cannot be attained. Simple molecules attached to the substrate via much weaker physical interactions (such as van der Waals forces) will have a good mobility; but they cannot form bound lubrication coating. The proposed ionic polymer lubricant approach is to find a balance between these strong and weak interactions. The ionic polymer lubricants will have electrostatic interactions with the substrate through their ionic groups as well as van der Waals interactions. The electrostatic interaction between the ionic group and the substrate will provide strong adhesion of the lubricant molecule. Unlike covalent chemical bonding, the electrostatic interactions are isotropic so ionic pairs can easily be formed and dissociated as long as the charge neutrality is conserved. This will make the lubricant molecule "bound yet mobile" on the substrate surface. With the lateral mobility, the lubricant layer can repair (self-heal) the wear region by flowing from the surrounding region. The proposed study will provide fundamental understandings on how the ionic polymer molecule interacts and reacts with solid substrates and how the ionic polymer molecule adsorbed on the solid surface respond to the mechanical and tribological stimuli. This knowledge will be a valuable database to understand the structure-property relationship of ionic polymer molecules and develop better organic coating materials for various applications in nanotechnology and information technology. This project will also give graduate students a multidisciplinary training covering organic chemistry, surface chemistry, material science, tribology, and nanotechnology. The students trained with these multidisciplinary skills are in urgent need for fast growth of newly emerging nano-engineering fields.