We propose to combine surface sensitive infrared-visible sum frequency generation spectroscopy (SFG) with insitu friction and adhesion measurements. The experiments are motivated by results of Chaudhury and Brown using poly (dimethylsiloxane) (PDMS) lenses and Israelachvili using surface force apparatus; where they find a relationship between friction, adhesion hysteresis and mobility of the molecules at the interface. However, there is no information on how different relaxation processes are at polymer/solid or hidden interfaces in comparison to that in bulk. Recent experiments of glass transition temperature of polymer thin films indicate that the relaxation at the air interface can be several orders of magnitude faster than in the bulk. The relaxation times of polymer chains are expected to be altered in contact with surfaces of different surface energies. Furthermore, there is no direct information of the change in the structure of molecules at moving or sliding interfaces. Understanding these properties is crucial to understand friction. Recently, we demonstrated that SFG can be applied to study the contact interface between an elastomeric PDMS lens and a polymer or solid substrate. Here, we take advantage of this design to measure simultaneously the changes in structure between two sliding surfaces, friction and adhesion. In addition, we propose to measure the relaxation dynamics at interfaces using SFG to understand the relationship between mobility and friction coefficient. As a Director of District 5, I have been actively involved in organizing District 5 Science Day for students from K5-K12 for the past five years. In addition to this outreach activity, this proposal offers research opportunities to two high school students from a local high school to work during summer in my laboratory under the supervision of graduate students. The research of these high school projects can be submitted as a part of their science project for competition in the Intel Science and Engineering Fair. This effort will be integrated with the NSF-REU undergraduate program already existing at The University of Akron. Broader Impact: Friction between two surfaces is of utmost importance in a variety of technological and biological applications. The understanding and control of these phenomena will have a tremendous impact in conserving and using precious energy resources. The advances in this field are limited by the lack of understanding of the structure and properties of molecules at the interface. This proposal provides a new experimental method to probe molecular motion or deformation taking place at the interface and studies its relationship to friction and adhesion. This will broadly impact our design of surfaces, lubricants and micro or nano-actuators. The education and outreach activities target local schools in District 5 to promote an interest in science by encouraging students to undertake science projects and compete at district, state and international level.
