Direct Measurement of the role of Confinement and Chemistry on Local Physical and Mechanical Properties of Polymers

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The research objective of this award is to utilize techniques based on two different physics to investigate the thermal and mechanical properties of polymers near interfaces. In one case, nanoscale mechanical indentation is performed by measuring the force required to push small tips into the sample either from the top or side surfaces. In the second case, spectroscopy on embedded fluorescent probes measures the change in light emitted from the sample at different temperatures. These techniques are complimentary and orthogonal and both analyses can be performed on the same physical samples. Current literature reveals that substrate stiffness may play an important role in the effects on the confined polymer. After synchronization of the measurement techniques, we will investigate the mechanical interphase on a variety of substrates with different stiffness. This study will encompass rubbery substrates through high modulus silicon wafers. The effect of differences in polymer-substrate chemical interactions will also be investigated. Nanostructured polymers are important components of a variety of important systems, including lightweight structural materials, biomedical devices, and energy storage. Unfortunately, the unknown mechanical properties of confined polymers leads to uncertainty in design of novel devices and applications. Accurate assessment of interfacial polymer properties will allow for a more robust design space and tailoring of material properties to a higher degree. The proposed research will also serve as an excellent training platform for graduate students and postdoctoral fellows in the critical frontier of structure-based material design. Outreach to undergraduates, underrepresented groups and local middle-school students are included in the education plan, exposing larger societal groups to materials design principles and the technological development process. Students participating in this project will also have opportunities to collaborate with scientists at national labs (Argonne) and industries (Dupont and Boeing) in design projects.