59th Annual Report on Research 2014

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 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.

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.

Currently (September 2014) we are further modifying the SPR to conduct the very careful, and difficult experiments of bringing the polymer brushes that Ms. Wei synthesized close (within tens of nm) to a variety of solid substrates (test surfaces), both uncoated and coated with polymer. Using the signals from the SPR, we will be able to infer the conformational changes that the brush is undergoing as a function of distance from the test surface. This will be completed for a number of brush-coated surfaces, to generate a library of responses for multiple brush/test surface combinations. Once this is complete, we will gain access to a surface force apparatus (a few of these are available on campus) to further verify our results, and to possibly conduct tribological studies to discern how polymer conformation changes tribology.