Hydrogel is wobbly and glass hard
A new hydrogel has properties that were previously difficult to combine: it is soft and pliable, but at the same time does not burst even if an elephant stands on it. Twelve times in a row.
A hobby of material research teams working in the public eye is to "let the car run over" their research object. What (or who) can withstand this impressively shows even the interested layman how stable it (or he and she) is. Recently, the robustness of living beetles or extra-elastic-soft mini-robots was demonstrated in this way. Now it was "Super-Jelly's" turn to be rolled over: an innovative soft material that is suitable as a building material for all kinds of applications in which it is supposed to remain very stable and yet elastic and intact even under high pressure.
In the journal Nature Materials, Oren A. Scherman of the University of Cambridge and his collaborators describe the gel-like material; a highly compressible, glass-like, supramolecularly cross-linked polymer. The research group's goal was to construct a material with the properties of a hydrogel, but at the same time - unlike the typical hydrogel - tough enough not to be easily crushed under pressure. To this end, Scherman's team optimized the chemical scaffold that forms the core of the gel, which is 80 percent water.
At the core of the new molecular framework are glycoluriles, a molecule condensed from glyoxal and urea to form two organic ring structures. These glycoluriles can join together to form larger networks: the cucurbitils, macrocyclic giant molecules. These form a sponge-like network with water-filled cavities - and in Scherman and Co's hydrogel they serve as cross-links and interconnections of the linear polymer chains that form the backbone of the hyrogel. The trick: depending on which compounds are incorporated into the cavities, the material properties of the entire gel change from soft to hard or brittle to firm.
In the end, the scientists produced a gel that hardly yields to pressure: "We were surprised, says team member Jade McCune in a press release, that the gel is so difficult to compress. Chemical modifications to the guest molecules in the cucurbitil cavities significantly alter the properties. In the end, the scientists succeeded in turning a rather rubbery starting product into a glass-hard end product by experimenting with such modifications.
In principle, it is now conceivable to construct a wide variety of types alongside the new glassy hydrogel. According to the researchers, their product would now be able to withstand an elephant stepping on it - or a car rolling over it. The polymer network would not be damaged by twelve consecutive load-relief cycles with a compression pressure of 100 megapascals, would remain elastic and would regenerate completely within 120 seconds. The team hopes that the new material could be used in the future to create better implantable bioelectronic applications - or to build various other hydrogel-based applications that are both elastic and hard.
Spectrum of Science
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