CAREER: Vitrimer gels as a platform for homogenous and meso/nanostructured networks

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). NON-TECHNICAL SUMMARY:

A vitrimer is a relatively new type of polymer that is insoluble yet still flows at high temperatures. These paradoxical traits – not found in any other type of polymer – enable vitrimers to be mechanically robust, chemically resistant, and also recyclable. While vitrimer research has mostly focused on dry bulk materials, vitrimer gels (where the material is swollen with a liquid solvent) are also predicted to have unique properties.

Unlike conventional polymer gels, vitrimer gels are expected to have minimal structural defects. Increasing the interaction strength between the vitrimer and solvent is anticipated to induce the gel to assemble into a complex nanostructure. Such behavior invites the development of adaptable materials that switch properties on command, which are needed for creating safer batteries, and more efficient separations membranes and catalyst scaffolds.

To that end, this work will determine the molecular design principles of vitrimer gels. Through tuning the interactions between vitrimer and solvent, gels with either uniform or complex nanostructures will be realized. Success in this research will unlock a new generation of temperature responsive polymer materials with adaptable nanostructures.

Augmenting the research objectives, the education plan will encourage underrepresented minority (URM) high school students to pursue STEM PhD degrees. To achieve this goal, students from a local Tallahassee high school will be introduced to STEM role models and research opportunities through in-class science experiments and summer research internships in the PI’s laboratory.

TECHNICAL SUMMARY:

A vitrimer is a dynamic polymer network that has associative cross-links (XLs), which maintain network connectivity but undergo exchange reactions. Vitrimers express unique structural and thermodynamic traits that will open new pathways towards temperature responsive materials with adaptable meso- and nanostructures. Specifically, the proposed work will investigate vitrimer gels, where the network is swollen by solvent.

Theory and simulations predict that associative XLs cause vitrimer gels to have minimal network defects, and induce phase separation into vitrimer-rich and solvent-rich domains. To address the knowledge gap between theory and experiment, the PI and his students will elucidate how associative XLs affect vitrimer gel network topology and self-assembly.

The specific aims are to (I) develop synthetic routes to prepare model vitrimer gels, (II) investigate the network structure of homogeneous single-phase gels, and (III) examine the phase behavior and dynamics of meso- and nanostructured gels. The proposed approach will establish vitrimer gels as adaptable materials whose morphologies actuate in response to a stimulus, thereby satisfying urgent technological needs in energy storage, separations, and catalysis.

The main educational objective is to create an outreach program to encourage underrepresented minority (URM) high school students to pursue a PhD in STEM. Collaborating with a local high school, the program will introduce URM high school students to STEM role models and research opportunities by (I) guiding them through in-class polymer-related experiments and (II) placing rising URM high school seniors in summer research internships to work on vitrimer gel projects – thereby integrating the research and educational thrusts.

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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.