TAGS: Natural-based Adhesives
The scientists Hailong Fan and Jian Ping Gong from Hokkaido University have developed an adhesive that utilize electrostatic interaction to stick to negatively charged surfaces, such as rocks, glass and metals under the sea. Th e new adhesive overcomes the challenges of catechol-based glues which get easily oxidized and lose their adhesiveness and is inspired by organisms similar to mussels that fix themselves to underwater surfaces.
Electrostatic Interactions in Saline Water
The team built polymer chains made from two types of monomers as building blocks. One chain containing positively charged “cationic” residue and the other containing an “aromatic” ring. In biosystems, adjacent cationic aromatic amino acid sequences in proteins are known to facilitate electrostatic interactions in saline water. It has been challenging to introduce such sequences in synthetic polymers due to difficulties in controlling monomer sequences.
The scientists discovered that the synthetic polymers with adjacent cationic aromatic sequences could easily be manufactured using a highly scalable, cost-effective method called “cation–p complex-aided free-radical polymerization.”
Key Findings of New Adhesive
The scientists found that the two residue types in polymers bonded together to form a hydrogel that stuck well to negatively charged solid surfaces in saltwater, where adhesive strength approached approximately 60 kPa. Hydrogels are composed of a variety of cationic-aromatic monomer combinations and exhibited fast, strong but reversible adhesion to the surfaces.
Adhesion was largely due to the electrostatic interaction between the positively charged residues on the polymers and the negatively charged surfaces. But the polymers made from the cationic aromatic monomers without adjacent sequences were not nearly as adherent, indicating that adjacent aromatic residue enhances electrostatic interaction in high ionic strength environments.
Preserving Marine Environments
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Our sequence controlled polymeric hydrogel should have promising applications as glues for undersea leakage and sea sand binders for preserving marine environments and coagulants for concrete in the sea,” said Gong. The study also paved the way for further investigations into electrostatic interactions in highly ionic environments.
The study was published in Nature Communications and was conducted in part at the Institute for Chemical Reaction Design and Discovery (WPI-ICReDD) which was established at Hokkaido University in 2018 to advance our understanding of and efficiently develop chemical reactions.
Source: Hokkaido University