New Frameworks for Nanoscale Surface Functionalization of Amorphous Materials

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Claridge of Purdue University will design molecular building blocks that allow precise control over the surface chemistry of technologically important soft materials. The proposed work develops a new approach to on-surface diacetylene polymerization reactions, designing building blocks that exhibit long-range order, and that allow for atomic-scale motion during reaction, greatly improving reaction efficiency.

Together these capabilities create large polymers that efficiently transfer to the surfaces of materials with stiffness similar to human soft tissue. Ultimately, these building blocks 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. The proposal also includes an assessment/outreach strategy aimed at addressing gaps in national preparation of undergraduate students for STEM careers such as nanoscience, including students from underrepresented backgrounds.

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.

This project focuses on a class of monomers with a bioinspired architecture in which two alkyl diacetylenes are linked through a glycerol or similar core, since these monomers appear to undergo exceptional ordering and reactivity. The first two aims of this project are to understand the relationship between alkyl chain structure and core/linker structure, and polymerization efficiency.

The final stage of the project designs monomers with a new core architecture that leads to formation of 2D sheetlike polymers. The new classes of building blocks developed through this project have to the potential to lead to soft material 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.