Chemists can fine tune polymers by rearranging and modifying the molecular building blocks that form their long chains. In a recent JACS paper, researchers in the Lamb Lab at the University of Minnesota examined how a specific molecular feature dipoles affects polymer behavior.

Dipole dipole interactions are a powerful way to modify a polymer’s performance, from its mechanical strength to its barrier properties, explains Luc Wetherbee, PhD candidate in Chemistry and co author of the study. Adding polar side chains is known to enhance polymer properties compared to nonpolar versions, but studies on dipoles built directly into the polymer backbone have mostly dealt with relatively weak dipoles.

In their new work, the Lamb Lab designed monomers containing polar heterocycles ring structures with atoms such as nitrogen and oxygen fused to cyclic alkenes. Using a metal catalyst, these could be polymerized into chains with strong main chain dipoles. By adjusting the monomer design, the team could vary both dipole strength and orientation whether aligned along the polymer backbone or positioned perpendicular to it.

The researchers investigated how these structural differences influenced material properties using thermal and rheological analysis. Thermal analysis lets us track temperatures where phase changes occur, says Wetherbee. For instance, if a polymer’s glass transition temperature is higher, it might be because more heat is needed to overcome stronger dipole dipole interactions between chains. Rheology the study of how materials flow provided additional insight. In the Lamb Lab’s polar polymers, stronger dipoles consistently increased both the glass transition temperature and the activation energy of flow.Interestingly, these effects were even greater when strong dipoles were oriented perpendicular to the backbone, likely because this arrangement encourages interactions between neighboring chains.

The findings highlight how even subtle shifts in molecular structure such as dipole strength and orientation can significantly influence polymer performance. Polymer research in UMN Department of Chemistry is helping pave the way toward smarter, more sustainable materials for an efficient, responsible, and innovative future.

Founded in 2020 by Assistant Professor Jessica Lamb, the Lamb Lab works at the intersection of organic, physical organic, organometallic, and polymer chemistry. The group combines catalysis and physical organic techniques to create new polymers and small molecules, offering students interdisciplinary, hands on training. 

Source: https://cse.umn.edu/chem/news/building-better-polymers-new-research-jacs-lamb-lab