You can think of polymers as akin to trains: just like a train is made up of several cars, polymers consist of numerous monomers, and the connections between these train cars are akin to the chemical bonds that hold monomers together. Polymers serve a wide variety of purposes—from delivering drugs to being utilized in construction—but their structure and functionality are limited by the chemical similarity of their monomer components.
Recently, chemists from Scripps Research, along with other collaborators, have formulated a new reaction that allows for the creation of distinctive monomers in a precise manner. This reaction utilizes nickel as a catalyst, making it possible for scientists to engineer polymers with distinct and adjustable properties suitable for drug delivery, energy storage, microelectronics, and more. The findings were published in Nature Synthesis on August 8, 2024.
“This research demonstrates how utilizing earth-abundant metal catalysts can pave the way for new materials that possess exceptional structural and functional diversity,” notes senior author Keary Engle, PhD, a professor in the Department of Chemistry and the dean of Graduate and Postdoctoral Studies at Scripps Research.
The Engle lab at Scripps Research specializes in devising novel chemical reactions to synthesize a diverse range of small molecules, often targeting applications in drug discovery. In this research effort, the Scripps Research team teamed up with polymer experts from the Georgia Institute of Technology and the University of Pittsburgh to investigate if their techniques could be scaled up to produce unique polymers.
“The characteristics of polymers are largely influenced by the type of chemistry present in their backbone; therefore, by modifying the chemical properties of the building blocks, we can easily adapt them for the macromolecular structures we create,” explains Anne Ravn, PhD, a postdoctoral researcher in the Engle lab and co-first author of the study. “This project aimed to determine whether our approach for creating small molecules could be expanded to introduce new building blocks for polymer synthesis.”
The paper features additional first authors: Van Tran, PhD, who contributed as a graduate student in the Engle lab; Camille Rubel, a current graduate student in the lab; Mizhi Xu, PhD, a former graduate student in the Gutekunst lab at the Georgia Institute of Technology; and Yue Fu, PhD, a former graduate student in the Liu lab at the University of Pittsburgh.
For synthesizing the new monomers, the Scripps Research team developed a chemical reaction that modifies the structure of an initial molecule using nickel as a catalyst. This nickel-catalyzed process introduced two new “functional groups” to the molecule—small side chains that impart different chemical and physical traits to the resulting polymer, such as its flexibility, elasticity, or solubility.
Afterward, the collaborators at Georgia Institute of Technology employed another chemical reaction to link these monomers together through polymerization, producing polymers with a distinctive makeup.
“Most commercially available polymers have two carbons between each functional group that lack side chains, but in our case, the functional groups are positioned much closer together, resulting in materials with varied properties,” Ravn notes.
Looking ahead, the team intends to investigate how varying the functional groups on the monomers affects their characteristics.
“Our approach grants us the ability to ‘accessorize’ the molecule with much greater flexibility compared to other methods, which permits us to explore diverse functionalities within the building blocks,” says Ravn. “We are currently looking to broaden the method to study how introducing other types of functional groups impacts the material’s properties.”
As nickel is more plentiful than many other metallic catalysts commonly used in these chemical reactions, the researchers believe that their approach promises to be an environmentally sustainable option for polymer production. They are also considering ways to enhance the sustainability of the end products.
“From an environmental standpoint, we aim to devise a method to break down these lengthy polymers, allowing us to revert them to their original building blocks for reuse,” explains Ravn. “This is a tool we aspire to refine in the future to ultimately develop new technologies beneficial to society.”
“Ni-catalysed dicarbofunctionalization for the synthesis of sequence-encoded cyclooctene monomers” was co-authored by Ethan Wagner, Steven R. Wisniewski, Peng Liu, and Will Gutekunst from Scripps Research.
This research was supported by the Department of Energy (DESC0023205), the National Science Foundation (CHE-2102550), the Independent Research Fund Denmark (grant ID: 10.46540/3102-00009B), and the Schimmel Family Endowed Scholarship Fund.
