60th Annual Report on Research 2015

This investigation involves the use of surface plasmon resonance spectroscopy (SPR) to study the conformational changes of polymer-based brushes immobilized on solid surfaces when they are brought in close proximity to another surface. So far, the PRF funds have primarily been used to support Ms. Menglian Wei, a Ph.D. student in my group. This is a direct result of PRF funds being used to pay for her to be a research assistant (as opposed to a teaching assistant), which allows her to focus all of her efforts on this project. These funds have allowed her to be trained on a suite of imaging and analysis tools to study the synthesized thin films. Ms. Wei has also attended training classes on LabView programming, to help her develop skill required to develop a program to operate our in-house built SPR. These skills will be very important in her studies in the group and certainly when Ms. Wei moves on to her job search. Personally, the success of these studies will allow me to engage local oil companies, which are extremely important in this region of the world. Making these important connections will certainly lead to more funding of my research program, which will allow the group to continue to do high quality and world class research. Likewise, this will continue to allow me to train more personnel. Furthermore, success on this project will propel the group into new research directions and areas that would not have been possible without these funds. For example, since beginning these experiments, Ms. Wei has found some very interesting optical properties from the samples she is making, which she has exploited for other applications, in addition to the applications in this proposal. Finally, many others have been supported with funds from this grant, which can reap similar benefits as Ms. Wei.

Since beginning this project, Ms. Wei has fully completed the building of our SPR setup -- as noted in our proposal, the SPR was not complete when this project was submitted for funding. Critical to these studies was also generating very well-defined polymer brushes on Au (SPR) surfaces. To accomplish this, Ms. Wei completed countless experiments to optimize the polymerization. She also fully characterized each resulting brush by atomic force microscopy (AFM), ellipsometry, and scanning electron microscopy to determine the surface coverage and uniformity of the films. These studies were completed with the assistance of Mr. Yongfeng Gao (Ph.D. student in my lab), and Dr. Molla Islam (postdoc in my lab). After much experimentation, she was able to determine optimal conditions for yielding the required polymer thin films.

The in-house built SPR has been further modified to study polymer conformation when confined. Specifically, an additional surface (coated or uncoated with polymer thin film) has been brought close or far away from SPR sensor chip in a controlled manner with resolution down to 0.3 nm. Using the signal from SPR, the conformation of polymer thin film on SPR sensor chip has been studied as a function of distance from the test surface. The preliminary results will be correlated to data obtained from a surface force apparatus, which will allow us to understand how the conformation affects tribology.

Currently, experiments on a library of polymers are being conducted such that we can obtain a better understanding of the fundamental properties that dictate tribology. PRF funds have allowed us to finally get to this point, which will lead to innovation in the area of new and improved surface coatings.