Detaching glue with light: possible thanks to a supramolecular adhesive

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Colle réversible réactive à la lumière.  Photo
Colle réversible réactive à la lumière. Photo

Something went wrong when gluing something? No problem. Researchers have developed a polymer structure which is capable of reversibly gluing materials together using nothing but light.

Whether it is the badly glued handle of a coffee cup or an out-of-date advertisement on a department store window, there are certain things which need to be attached or glued more than once without a lot of trouble. Researchers at the Adolphe Merkle Institute (AMI) of the University of Fribourg have now succeeded in making this possible: Senior Research Associate Dr. Gina Fiore and PhD candidate Christian Heinzmann, under the direction of Prof. Christoph Weder, have developed a polymer structure whose cross-linking can be unlinked by irradiation with light and then linked again. It is the first time that a supramolecular adhesive has been developed which can reversibly change the adhesive properties upon exposure to ultraviolet light. The research results have been published as the “Editors’ Choice“ in the scientific journal ACS Applied Materials & Interfaces.

Light and Heat
The secret behind this new material lies in the supramolecular cross-linking components. Unlike conventional polymers consisting of long, chain-like molecules made up of thousands of atoms, these particular polymers are composed of smaller molecular components which have “sticky” cross-linking components at their ends. These “sticky ends” connect the short polymer chains to form long chains, but this process is reversible. The cross-linking components used are either metal ions with complexing structures (two-component system), or a hydrogen bonding based system (single component system). The so-called sticky ends of such a polymer structure can be altered upon exposure to (ultraviolet) light, which liquefies the polymer and results in easier separation of the bonded joint. If the light is removed, the polymers harden again.
This process can also take place by the application of heat. “The advantage of this is its ease of use”, says Christian Heinzmann. “For example, the advertisement attached to a shop window can be removed simply by using a blow-dryer.” The sensitivity to heat can also be adapted to the environment: polymers used in the Arctic require a different heat sensitivity than those used on a shop window exposed to the sun in summer.

The reversible adhesive is based on the same findings as those relating to self-healing materials published by Christoph Weder and his colleagues in 2011. The feasibility studies have not yet resulted in a practical application, however discussions on the self-healing materials are proceeding with the industry.

Link to the Publication: