NSF Award
2404367
With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Drs. Kevin Noonan, Tomasz Kowalewski and Linda Peteanu of Carnegie Mellon University will explore a new class of optoelectronic macromolecules that spontaneously twists into a spiral or helical shape, not unlike some biological molecules such as proteins or DNA. What makes these novel molecules unique in comparison with their biological counterparts is that electrons forming the backbone bonds are not strictly confined and can transport electrical currents and convert light into electricity or vice versa. The team will use a wide range of characterization techniques to better understand how the precise structure of these molecules makes them adopt the helical shapes, control the way they turn (like right-hand or left-hand screws) and allows them to reversibly unfold/refold under the influence of external conditions. All these dynamic features will be controlled through precise chemistry and the resulting molecules will be explored as active components for molecular electronics, catalysis, and hierarchical nanomaterials. Since the work is highly interdisciplinary, students participating in this project will develop skill sets in chemical synthesis, molecular/structural analysis, and computational quantum chemistry. In addition, the research team will be active in the local community, working to foster interest and excitement in the molecular sciences.<br/><br/>The project is focused on a family of conjugated helical furan polymers and macrocycles and will advance their synthesis and elucidate their properties as well as self-assembly behavior. The research is prompted by a recent discovery of a powerful structure directing effect of ester side groups in -linked alkyl furan-3-carboxylates, which forces adjacent furan repeat units to adopt a syn-conformation and twists the molecules into macrocycles and helical chains. The resulting poly(3-hexylesterfurans) are quite distinct relative to other conjugated helical polymers since they adopt tight helical conformation with only 6.5 repeat units per turn, which effectively turns them into compact, conjugated nanoparticles with a central core void lined with oxygen atoms. Cross-coupling tools will be perfected to allow expansion of this family to other heterocycles and side chain groups with precise control of composition, sequence, and molecular weights. Chiral structure-directing side chains will be used to impart chirality to supramolecular assemblies. The proposed structural and computational studies are directed at elucidating how the precise structure of macrocycles and polymers guides the process of their self-assembly into supramolecular structures. Particular attention will be given to understanding the chain folding process of polymers and the structure-directing effects originating from the presence of chiral groups. Furthermore, chiral polyfurans represent a new addition to the field of chiral conjugated polymers with envisioned unique applications in areas such as chiral electrochemical sensing, electron spin filters, and magneto-optics.<br/><br/>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.
