Precision Monolayer Chemistry on Amorphous Materials

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With support from the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program in the Division of Chemistry, Shelley Claridge at Purdue University is studying fundamental processes that allow precise control over the surface chemistry of technologically important amorphous materials. If better understood, these processes could enable design and fabrication of surfaces with well-defined chemical instructions for processes ranging from the assembly of materials for solar energy conversion to materials that scaffold the growth of cells to repair injuries. In this project, the progress of a class of surface reactions will be monitored using specialized microscopes that enable imaging at the scale of individual molecules. This information is integrated with larger-scale experimental techniques including fluorescence microscopy, providing a molecular-to-a macroscopic view of the reaction progress. As part of this project, Dr. Claridge is working with graduate students in her research group and with minority-serving undergraduate institutions to develop a series of educational experiences and resources that help undergraduate students analyze and communicate scientific findings, as a foundation for their future careers in science. This project utilizes striped phases of functional alkyl diacetylenes known to assemble on graphite and other two-dimensional materials as a basis for functionalizing the surface of amorphous elastomeric materials such as polydimethylsiloxane (PDMS) that exhibit substantial nanoscale heterogeneity. In this strategy, the diacetylene monomers are assembled on graphite, photo-polymerized by irradiation with ultraviolet light, then covalently transferred to the PDMS surface using the hydrosilylation reaction that is the basis for PDMS curing. The first two aims of this project are to understand the relationship between diacetylene monomer structure and striped phase monolayer polymerization efficiency, and to understand the relationship between PDMS component structure (vinyl-functional base polymer and hydrosilyl groups in crosslinker) and reactivity with the striped polydiacetylene layer. The final stage of the process characterizes the function of monolayers on PDMS based on their ability to control isotropic and anisotropic particle adsorption. Understanding and control of the striped phase polydiacetylene polymerization reaction, transfer reaction, and surface functionality has to the potential to lead to surfaces that carry embedded chemical instructions for applications including wearable electronics, chromatography, and cell culture.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.