Multi-Molecular Adhesive

Supramolecular Adhesive

Supramolecular Adhesive Suitable for Use Up to 400 Degrees Celsius

Researchers have developed a supramolecular adhesive with reversible properties and superior adhesion characteristics that functions across an exceptionally wide temperature range, from liquid nitrogen (-196 degrees Celsius) to oven temperatures (200 degrees Celsius). Unlike standard adhesives, supramolecular adhesives do not provide adhesion through cross-linking of molecular components with one another. Instead, during curing, they create a self-assembly in which the bonded puzzle pieces become tightly bound together. Researchers are interested in such supramolecular systems because they can provide sustainability, are customizable on demand, can in principle have their starting materials recovered, and their chemical activity can be modified. However, to date, the performance of such adhesives has not exceeded a certain acceptable threshold, and it remains true that they are highly dependent on environmental conditions. Developed by a research team led by Kai Liu from Tsinghua University in Beijing, China, this new supramolecular adhesive consists of two components, one of which is a protein synthesized within a specially modified bacterium. The other component is a crown ether, a ring-shaped molecule that wraps tightly around another molecule, much like a crown on a queen's head. The researchers observed tight interactions between molecules in these adhesive systems. By bringing the crown ether and protein together and heating the solution for curing purposes, the crown ether was made to adhere to the protein surface. The research team observed that the crown ether and protein bind tightly to one another through opposite charges and the interaction of other molecules, creating a new, interlocked structure that 'welds' the proteins together. As a result, an exceptionally strong adhesive effect was achieved. Steel plates bonded together were observed to withstand high shear forces at room temperature, in liquid nitrogen, and at 200 degrees Celsius. The adhesive performed well with different materials and even underwater. Achieving success under such a wide spectrum of working conditions is rare even in specialty adhesives, and it is certainly accurate to say this represents a first for supramolecular adhesives. The ability to separate the interlocked components for recycling and the fact that the reused adhesive retains nearly all of its strength is promising. According to the researchers, this exceptional adhesive effect is caused by the activation of specific supramolecular interactions, particularly at low temperatures. The tight interlocking of the components pushed water away from the protein surface. Thus, as in antifreeze, the formation of ice crystals in the frozen state was prevented, a condition that would lead to premature failure in many conventional adhesives. The researchers suggest that this new adhesive could be used in the manufacturing of specialized components that will be subjected to highly variable conditions during use; for example, the wide temperature ranges to which spacecraft are exposed.

Source

Provided by Wiley / More information: Kelu Zhao et al, Molecular Engineered Crown-Ether-Protein with Strong Adhesion over a Wide Temperature Range from −196 to 200°C, Angewandte Chemie International Edition (2022). DOI: 10.1002/anie.202207425 Journal information: Angewandte Chemie International Edition, Angewandte Chemie / https://phys.org/news/2022-07-supramolecularadhesive-usable-temperature-range.html