Building better polymers: New research in JACS from the Lamb Lab

MINNEAPOLIS / ST. PAUL (08/13/2025) – Polymers are long chains of molecules that make up many of the materials we use every day: from plastic shopping bags, to sneakers, to chewing gum. Chemists can alter these materials by rearranging and adjusting the building blocks that make up the chains. In a recent paper from the Lamb Lab, UMN chemists explore how a certain type of molecular property, dipoles, affect the way polymers behave.

“Dipole-dipole interactions are a powerful tool for altering the performance of polymers, including their mechanical strength and barrier properties,” Luc Wetherbee, paper co-author and Chemistry PhD candidate, writes. “While the addition of polar side chains has been shown to enhance the properties of polymers relative to their nonpolar counterparts, previous studies investigating the effect of dipoles within the polymer backbone are limited to fairly weak dipoles.” In their newly published research, the Lamb Lab uses monomers containing polar heterocycles—rings containing atoms like nitrogen and oxygen—fused to cyclic alkenes that can be polymerized using a metal catalyst, allowing for polymers with strong main-chain dipoles. Through careful monomer design, these polar heterocycles can be varied both in the strength of the dipole and the dipole’s orientation, or whether the dipole is oriented along the polymer backbone or perpendicular to it.

The Lamb research team probed the effects of these structural differences by analyzing thermal and rheological properties. “Thermal analysis can be used to compare the temperature of different phase changes; for example, if a polymer begins to flow at a higher temperature–also known as the glass transition temperature–this could be because more heat is required to overcome stronger dipole-dipole interactions between polymer chains,” Wetherbee says. Rheology, the study of a material’s flow, tells chemists a lot about its physical behavior. In the Lamb Lab’s polar polymer samples, incorporating a stronger dipole predictably increased the glass transition temperature and the activation energy of flow (or how much energy is required to overcome the dipole-dipole interactions hindering the polymer from flowing). Additionally, the glass transition temperature and activation energy of flow increased when the strong dipoles were oriented perpendicular to the polymer backbone, suggesting that dipoles facing away from the polymer chain facilitates the formation of dipole-dipole interactions between polymer chains. 

This research shows how subtle changes in molecular structure, like dipole strength and orientation, can have a significant impact on material performance. Polymer research in the UMN Department of Chemistry plays a key role in the effort to design smarter, more sustainable polymers for a future that’s efficient, responsible, and innovative.

Founded in 2020 by Assistant Professor Jessica Lamb, the Lamb Lab’s research is at the interface of organic, physical organic, organometallic, and polymer chemistry. With a strong focus on applying catalysis and physical organic techniques to the synthesis of new polymers and small molecules, students in the group receive dynamic and interdisciplinary training. To learn more about research in the Lamb Lab, click here.