A team of researchers led by Professor Dong Woog Lee from the Department of Chemistry at the Ulsan National Institute of Science and Technology (UNIST), in collaboration with Professor Byeong-Su Kim from the Department of Chemistry at Yonsei University, has uncovered a groundbreaking discovery in the field of synthetic polymers. Their study reveals that synergistic anion–π interactions are crucial in enhancing the cohesion of polymers. This work, which bridges the gap between biomolecular interactions and synthetic materials, offers promising insights into creating stronger, more versatile polymers for a range of applications.
The research, recently published in the Proceedings of the National Academy of Sciences, explores the significant role of anion–π interactions—a type of non-covalent bond formed between negatively charged molecules (anions) and the π electron systems of aromatic rings. While these interactions are already known to play vital roles in various biological processes, such as enzyme catalysis and ion transport, their application in the design of synthetic polymers has been largely unexplored until now.
To understand how anion–π interactions could be harnessed to improve polymer cohesion, the researchers drew inspiration from mussel foot proteins, which are renowned for their remarkable adhesive properties in marine environments. Mussels possess foot proteins that allow them to cling to rocks and other surfaces, even underwater, a feature that is largely attributed to the presence of specific amino acids in these proteins, particularly 3,4-dihydroxyphenylalanine (DOPA) and aspartic acid.
The team focused on these key components, known for their strong binding capabilities, and analyzed their structural characteristics to replicate them in synthetic polymers. By understanding how these natural proteins leverage molecular interactions, the researchers were able to design functional monomers that mimic the structural features of DOPA and aspartic acid, creating a novel polymer that could potentially mimic the cohesive strength of mussel foot proteins.
The innovative polymer synthesized in this study was designed with monomers that incorporated the DOPA-like structure, providing the π-electronic field characteristic of aromatic rings, while the aspartic acid-like monomer introduced the anion needed for anion–π interactions. To experimentally test the polymer’s cohesion under different conditions, the research team employed a surface force apparatus (SFA), a tool that allows for precise measurements of molecular forces between surfaces.
The researchers tested the cohesion of the polymer in both neutral and acidic environments. In neutral conditions, where the polymer’s functional groups are ionized, the anion–π interactions served as the principal bonding force, significantly enhancing the cohesion of the polymer. This finding provides experimental confirmation of the critical role that these interactions play in strengthening polymer cohesion. However, when the polymer was exposed to acidic conditions, where the functional groups remained non-ionized, the cohesion weakened, as hydrogen bonding became the dominant interaction.
This discovery is pivotal because it represents the first experimental evidence showing how anion–π interactions contribute to the cohesion of synthetic polymers, a process that had only been theorized before. The study highlights the importance of considering complex intermolecular interactions in the design of advanced materials, moving beyond traditional covalent bonding to incorporate interactions commonly observed in biological systems.
The implications of this study are far-reaching. By demonstrating how anion–π interactions can enhance polymer cohesion, the researchers open up new possibilities for designing high-performance polymers with improved strength, stability, and versatility. These polymers could have a wide range of applications, including in the development of adhesives, self-assembly systems, catalysts, and drug delivery technologies.
In particular, the ability to design polymers that can mimic natural adhesive processes opens up exciting possibilities for the creation of new materials that are both strong and flexible. These materials could find use in industries such as biomedical engineering, where strong, biocompatible adhesives are needed for applications like wound care and tissue engineering. Similarly, the study’s insights could lead to breakthroughs in drug delivery systems, where polymers with enhanced cohesion can be used to deliver therapeutic agents more effectively and with greater precision.
Moreover, the concept of using anion–π interactions to strengthen polymers could lead to more sustainable materials, as these interactions are non-toxic and require fewer resources to form than traditional covalent bonds. This approach could contribute to the growing field of green chemistry, which seeks to develop environmentally friendly materials and processes.
More information: Seunghyun Lee et al, Synergistic anion–π interactions in peptidomimetic polyethers, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2419404122