New chainmail-like materials could possibly be the way forward for armor

In a exceptional feat of chemistry, a Northwestern College-led analysis crew has developed the primary two-dimensional (2D) mechanically interlocked materials.

Resembling the interlocking hyperlinks in chainmail, the nanoscale materials reveals distinctive flexibility and energy. With additional work, it holds promise to be used in high-performance, lightweight physique armor and different makes use of that demand light-weight, versatile and hard supplies.

Publishing on Jan. 17 within the journal Science, the research marks a number of firsts for the sphere. Not solely is it the primary 2D mechanically interlocked polymer, however the novel materials additionally comprises 100 trillion mechanical bonds per 1 sq. centimeter—the very best density of mechanical bonds ever achieved.

The researchers produced this materials utilizing a brand new, extremely environment friendly and scalable polymerization course of.

“We made a very new polymer construction,” stated Northwestern’s William Dichtel, the research’s corresponding creator.

“It is much like chainmail in that it can not simply rip as a result of every of the mechanical bonds has a little bit of freedom to slip round. In case you pull it, it could dissipate the utilized pressure in a number of instructions. And if you wish to rip it aside, you would need to break it in lots of, many alternative locations. We’re persevering with to discover its properties and can in all probability be finding out it for years.”

Dichtel is the Robert L. Letsinger Professor of Chemistry on the Weinberg Faculty of Arts and Sciences and a member of the Worldwide Institute of Nanotechnology (IIN) and the Paula M. Trienens Institute for Sustainability and Power. Madison Bardot, a Ph.D. candidate in Dichtel’s laboratory and IIN Ryan Fellow, is the research’s first creator.

Inventing a brand new course of

For years, researchers have tried to develop mechanically interlocked molecules with polymers however discovered it close to unimaginable to coax polymers to type mechanical bonds.

To beat this problem, Dichtel’s crew took a complete new strategy. They began with X-shaped monomers—that are the constructing blocks of polymers—and organized them into a selected, extremely ordered crystalline construction. Then, they reacted these crystals with one other molecule to create bonds between the molecules throughout the crystal.

“I give a variety of credit score to Madison as a result of she got here up with this idea for forming the mechanically interlocked polymer,” Dichtel stated. “It was a high-risk, high-reward concept the place we needed to query our assumptions about what sorts of reactions are doable in molecular crystals.”

The ensuing crystals comprise layers and layers of 2D interlocked polymer sheets. Throughout the polymer sheets, the ends of the X-shaped monomers are bonded to the ends of different X-shaped monomers. Then, extra monomers are threaded via the gaps in between. Regardless of its inflexible construction, the polymer is surprisingly versatile.

Dichtel’s crew additionally discovered that dissolving the polymer in resolution triggered the layers of interlocked monomers to peel off one another.

“After the polymer is shaped, there’s not a complete lot holding the construction collectively,” Dichtel stated. “So, once we put it in solvent, the crystal dissolves, however every 2D layer holds collectively. We will manipulate these particular person sheets.”

To look at the construction on the nanoscale, collaborators at Cornell College, led by Professor David Muller, used cutting-edge electron microscopy strategies. The photographs revealed the polymer’s excessive diploma of crystallinity, confirmed its interlocked construction and indicated its excessive flexibility.

Dichtel’s crew additionally discovered the brand new materials will be produced in giant portions. Earlier polymers containing mechanical bonds usually have been ready in very small portions utilizing strategies which might be unlikely to be scalable. Dichtel’s crew, then again, made half a kilogram of their new materials and assume even bigger quantities are doable as their most promising purposes emerge.

Including energy to powerful polymers

Impressed by the fabric’s inherent energy, Dichtel’s collaborators at Duke College, led by Professor Matthew Becker, added it to Ultem. In the identical household as Kevlar, Ultem is an extremely robust materials that may stand up to excessive temperatures in addition to acidic and caustic chemical substances.

The researchers developed a composite materials of 97.5% Ultem fiber and simply 2.5% of the 2D polymer. That small proportion dramatically elevated Ultem’s general energy and toughness.

Dichtel envisions his group’s new polymer may need a future as a specialty materials for lightweight physique armor and ballistic materials.

“Now we have much more evaluation to do, however we are able to inform that it improves the energy of those composite supplies,” Dichtel stated. “Nearly each property now we have measured has been distinctive not directly.”

Steeped in historical past

The authors devoted the paper to the reminiscence of former Northwestern chemist Sir Fraser Stoddart, who launched the idea of mechanical bonds within the Nineteen Eighties. Finally, he elaborated these bonds into molecular machines that change, rotate, contract and develop in controllable methods.

Stoddart, who handed away final month, obtained the 2016 Nobel Prize in Chemistry for this work.

“Molecules do not simply thread themselves via one another on their very own, so Fraser developed ingenious methods to template interlocked constructions,” stated Dichtel, who was a postdoctoral researcher in Stoddart’s lab at UCLA.

“However even these strategies have stopped in need of being sensible sufficient to make use of in huge molecules like polymers. In our current work, the molecules are held firmly in place in a crystal, which templates the formation of a mechanical bond round every one.

“So, these mechanical bonds have deep custom at Northwestern, and we’re excited to discover their potentialities in ways in which haven’t but been doable.”