Researchers are creating a new class of materials called “vitreous gels”

Scientists have created a new class of materials called “vitreous gels” that are very hard and difficult to break despite being more than 50% liquid. Coupled with the fact that glassy gels are easy to produce, this material holds promise for a variety of applications.

An article describing this work, titled “Solvent-Strengthened Glass Gels,” appears in the journal. Nature.

Gels and glassy polymers are classes of materials that have historically been considered distinct from each other. Glassy polymers are hard, rigid and often brittle. They are used to make things like water bottles or airplane windows. Gels – like contact lenses – contain liquid and are soft and flexible.

“We’ve created a class of materials we’ve called glassy gels, which are tough like glassy polymers, but—if you apply enough force—they can stretch up to five times their original length before breaking,” says Michael. Dickey, corresponding author of the article on the work, and Camille and Henry Dreyfus, professor of chemical and biomolecular engineering at North Carolina State University. “What’s more, once the material is stretched, you can use heat to force it to return to its original shape. In addition, the surface of glass gels is highly adhesive, which is unusual for hard materials.”

“The key thing that distinguishes glassy gels is that they are more than 50% liquid, which makes them more efficient conductors of electricity than ordinary plastics with comparable physical properties,” says Meixiang Wang, co-author of the paper and a postdoctoral fellow. researcher at NC State. “Given the number of unique properties they have, we are optimistic that these materials will be useful.”

Vitreous gels, as the name suggests, are essentially a material that combines some of the most attractive properties of both glassy polymers and gels. To make them, scientists start with liquid glassy polymer precursors and mix them with an ionic liquid. This combined liquid is poured into a mold and exposed to ultraviolet light, which “hardens” the material. The mold is then removed, leaving behind a glassy gel.

“An ionic liquid is a solvent, like water, but made entirely of ions,” says Dickey. “Normally, when you add a solvent to a polymer, the solvent pushes the polymer chains apart, making the polymer soft and stretchy. That’s why a wet contact lens is pliable and a dry contact lens isn’t. In glass gels, the solvent pushes the molecular chains in the polymer apart , which allows it to be expandable like a gel.

“However, the ions in the solvent are strongly attracted to the polymer, which prevents the polymer chains from moving. The inability of the chains to move is what causes it to be glassy. The end result is that the material is hard due to attractive forces, which is why the material is glassy.” .” but it’s still able to stretch because of the greater spacing.”

The researchers found that glassy gels can be made with a variety of polymers and ionic liquids, although not all classes of polymers can be used to make glassy gels.

“Polymers that are charged or polar hold promise for glassy gels because they are attracted to the ionic liquid,” says Dickey.

When tested, the researchers found that the glassy gels did not evaporate or dry out, even though they were 50-60% liquid.

“Perhaps the most interesting characteristic of glass gels is how sticky they are,” says Dickey. “Because while we understand what makes them hard and stretchy, we can only speculate about what makes them so sticky.”

The researchers also think glassy gels hold promise for practical applications because they are easy to make.

“Creating glass gels is a simple process that can be done by curing in any type of mold or 3D printing,” says Dickey. “Most plastics with similar mechanical properties require manufacturers to create the polymer as a raw material and then transport it to another facility where the polymer is melted to form the final product.

“We are excited to see how glassy gels can be used and are open to working with collaborators to identify applications for these materials.”

The paper was co-authored by Xun Xiao of the University of North Carolina at Chapel Hill. The article was co-authored by Salma Siddika, Ph.D. student at NC State; Mohammad Shamsi, former Ph.D. student at NC State; Ethan Frey, a former student at NC State; Brendan O’Connor, professor of mechanical and aerospace engineering at NC State; Wubin Bai, professor of applied physical sciences at UNC; and Wen Qian, research associate professor of mechanical and materials engineering at the University of Nebraska-Lincoln.