CAREER: Impact of Nanoconfinement on Large-Scale Dynamics of Polymers

TECHNICAL SUMMARY:

The dynamic behavior of polymers near interfaces is critical to performance in a broad range of high-technology applications. The objective of this CAREER research is to develop an understanding of the parameters controlling the diffusion of polymers nanoconfined between interfaces and to use this information to construct theories that enable predictive capabilities. The dependence of bulk polymer diffusion on fundamental variables, such as chain length and temperature, is well understood and this information will provide a strong foundation for comparison of diffusion at the nanoscale. In this research, the diffusion of polymers nanoconfined between well-controlled planar interfaces will be studied using fluorescence techniques. Living polymerizations will be used to synthesize polymers with low polydispersity indexes containing covalently-bound, thermally-stable fluorophores that do not affect the glass transition of the film. The proposed research program seeks to: 1) Determine how diffusion coefficients of simple polymers composed of chemically identical units (i.e. homopolymers) are affected by the size of the confining dimension and by interactions between the polymer and the confining interfaces. 2) Identify the relationships between chain architecture and the fundamental mechanisms of interfacial diffusion by varying backbone rigidity, chain linearity (branched or star polymers), and by employing model block copolymers that self-assemble in specific ways when confined between interfaces with differing surface chemistry. 3) Develop theories, ascertain scaling relationships and construct predictive models that enhance capabilities for designing high-performance nanostructured materials.

NON-TECHNICAL SUMMARY:

The objective of this project is to perform a study of polymer molecule movement parallel to surfaces when the surfaces are separated by a distance comparable to the size of the polymer molecule. This understanding is important in a variety of technological applications, such as hard drive lubrication and microelectronics manufacturing, and in biological processes within cells. For example, certain properties of polymers can be improved by mixing polymers with clay; this study will help explain how the polymer moves in spaces between individual clay particles during the mixing process. The overall result of this project will be a more comprehensive understanding of the factors that control polymer motion near and in-between surfaces which will improve design rules for new advanced materials and enhance the understanding of polymer physics. To complement the research, the outreach and educational component of this CAREER project is to revive and expand the interest of society and students at all levels in STEM careers, especially targeting those who represent diversity with respect to economic status, ethnicity and gender. The CAREER award will allow the PI to develop a Minority Teaching Fellows program that pairs graduate student colleagues with minority teachers from Title 1 high-schools to conduct cutting-edge research and develop new high-school curricula involving modern issues of polymeric materials. Through active participation, graduate students will also develop new appreciation for current issues of math, science and engineering education and societal viewpoints of careers in these disciplines. Additionally, to more broadly reach K-12 students, the PI and graduate student colleagues will develop Engineering Expeditions modules to be incorporated into Explore UT, an on campus day of performances, exhibits, lectures and hands-on activities. This event is free and involves a broad cross-section of the public and K-12 students from all over the State of Texas with whom the PI and graduate students will interact through hands-on demonstrations highlighting 'why plastics do what they do'.