Hydrogel becomes hard like glass at high pressure

Robert Klatt

Hydrogels are usually very elastic and soft. Scientists have now developed a hydrogel that does not deform under high pressure, but becomes as hard as glass.

Cambridge (England). Hydrogels can bind large amounts of water, but are not themselves water-soluble. They consist of cross-linked polymers, the properties of which can be varied in many ways by adjusting the cross-connections. In nature, hydrogels use snails and jellyfish, which are almost entirely made of this material. In the meantime, however, science has also recognized the different uses of hydrogels. Among other things, they are used in medicine to close intestinal wounds or to treat skin injuries without scars, but also as underwater glue.

Now scientists have the University of Cambridge a hydrogel develops that does not deform under high pressure, but becomes as hard as glass. According to their publication in the specialist magazine Nature Materials The researchers working with Zehuan Huang observed that crosslinkers give way very easily in most hydrogels because they are mostly based on non-covalent bonds such as hydrogen bonds.

Supramolekulare Polymernetzwerke

“We suspect that extending the shelf life of these crosslinkers will make it possible to create supramolecular polymer networks that behave like glass-like materials,” explains Huang. They therefore developed a hydrogel in which the cross-connections consist of cucurbiturils. These are cage-like organic molecules that connect the opposing crosslinkers more tightly. As a result, the crosslinkers only react slowly to forces that pull apart.

Hydrogel can withstand high pressure

Laboratory experiments and driving over with a 1.2 ton car show how much the newly developed hydro money can be burdened. The hydrogel can withstand pressures of more than one gigapascal. That is ten thousand times higher than atmospheric pressure on earth. Instead of deforming and being crushed in the process, the new hydrogel became hard as glass under the heavy load. “The way the hydrogel withstood compression was surprising – we hadn’t seen anything like this in hydrogels before,” explains Jade McCune.

Glasartiges Hydrogel

“To the best of our knowledge, this is the first time that vitreous hydrogels have been made. We are opening a new chapter in the field of high-performance gels, ”says Huang. The developers believe that there are many practical uses for the new hydro money.

“People spent years making rubbery hydrogels, but that was only half the picture. We have now developed a new class of materials that can cover the entire range from rubber-soft to glass-hard, ”explains Oren Scherman. By modifying the crosslinker ends, the scientists can precisely control how hard the gel becomes under pressure.

Nature Materials, doi: 10.1038/s41563-021-01124-x

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