Local Polymer Interfacial Mechanics: Effect of Topological and Chemical NanoPatterning

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This grant will answer open questions about the dynamic-mechanical properties of polymers in close proximity to surfaces (within tens to hundreds of nanometers) with varying geometric confinement and chemical functionalities. Small scale, local polymer behavior near surfaces dramatically affects the mechanical behavior of polymers in thin films, nanoscale structures in microelectronics, drug delivery devices, and nanocomposites, not only locally, but also at the bulk scale. Mechanistic understanding of, and control over, these local interphase properties is a crucial factor for the design and manufacture of economically and technologically important products and processes, from aircraft structural composite components to zero-emission vehicle power sources. This project will use small scale experimental methods in conjunction with computational modeling to develop a deep understanding of the local polymer interfacial mechanics to advance optimal material design. As such, the project will provide cross-disciplinary training to a diverse group of postdoctoral, graduate, and undergraduate trainees, enable community outreach by engaging with local K-12 science events, and contribute to digital data curation and distribution platforms.The goal of this research is to characterize the local mechanical gradients in confined polymers by applying advanced atomic force microscopy nanoindentation experiments coupled with targeted finite element analysis simulations to novel polymer-substrate interface model systems. Due to the generally complex configuration of polymers in various applications, model substrate systems will be designed to study multi-body compound effects arising from simultaneous interactions of local polymer domains with multiple functional interfaces. A suite of polymer-substrate interface samples containing topological and chemical patterns will be fabricated using lithography techniques. Local elastic modulus gradients will be mapped at high resolution using a coupled experimental and simulated approach such that data analysis will enable deconvolution of complex experimental artifacts. Advanced dynamic atomic force microscopy modes will also be employed to assess local changes in polymer dynamics. The model systems are fabricated as well-defined mimics of confined polymers in actual materials applications and provide an avenue for increased characterization efficiency by leveraging a combinatorial approach. To accelerate data collection and analysis, substrate samples will be designed such that many interphase conditions can be probed within one single sample. Overall, the investigations will provide key fundamental insights into the nature and impact of confined polymers and enable the rational design of multifunctional and robust systems using polymers and composites.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.