The new self-healing polymer has a quality that you’ve never seen before

What if there was a fabric that could help you heal and bullets like Superman? Such super-large action-driven polymers may actually help protect the real flyers of the universe.

Materials scientists at Texas A&M University have developed such a polymer with unique self-healing properties that have never been seen before. When struck by a projectile, this material is so extended that when the projectile succeeds in passing it, it only takes a small amount of polymer. As a result, the remaining holes are much smaller than the projectile itself.

However, for now, this effect has only been observed at extreme temperatures and at nanoscales.

“This is the first time a material of any size has demonstrated this behavior,” says Dr. Svetlana Sukhishvili, professor in the Faculty of Materials Science and Engineering, working on the development of materials science and engineering. Their findings can be found in The Materials Today Journal.

“In addition to being super cool, the new polymer could have many uses, such as the windows in space vehicles become resilient due to the onslaught of micrometrics,” Thomas said.

Space vehicles are frequently fired in microintestinal myosoid bodies, which travel at speeds of 10 km/s. Micrometrics can drill holes in windows, but they are small, visible to the human eye. However, windows manufactured with this layer of polymer may maintain Tinier damage more than the meteor itself.

Thomas, who first proposed to put polymers into ballistic testing, said the key goal of this study was to design materials that protect structures such as space orbits and vehicles, and to use military equipment and body armor on Earth.

The incredible behavior occurs in a new solid polymer film when melted when impacted by a laser-fired high-speed projectile, and when cooled it returns to its original shape. The polymer does this by absorbing much of the kinetic energy produced by the projectile, and it stretches and liquefies the film as it continues its journey and eventually penetrates the film. Once the piercing is in, the polymer is quickly cooled, its covalent bond is reformed, returning to its original solid state, leaving small holes behind.

“The main goal of our job was to see if we could simultaneously provide material that would absorb a lot of kinetic energy per mass of the unit target from the fast projectile and allow for very rapid healing of the punctured area,” Thomas said.

“We wanted to be able to perform the intended function, such as carrying air or liquids, to remain sealed against such liquid losses across the material membrane.”

This material is a Diels-Adler Polymer or DAP, which is named for a dynamic covalent network that researchers can break and reform. It belongs to a class of materials called covalently bonded adaptive networks or cans. Other Diels-Adler networks have been reported in the scientific literature, but the specific chemistry, topology and self-repair quality of DAP are novel. The acronym for DAP can also be called a dynamic action-driven material for its ability to self-heal.

“When we were synthesizing DAP, we aimed to do that so that the polymer turns into a liquid when the temperature rises,” Sukhishvili said. “This feature was introduced to promote 3D printing, but we thought that the polymer could exhibit improved ballistic healing properties due to its ability to liquefy upon heating.”

“Polymers are great materials, especially DAP materials,” explained Thomas. “It’s hard and strong at low temperatures, so it’s elastic at high temperatures, and at even higher temperatures it’s easily flowing liquid.

Furthermore, he said the process reverses itself. “There’s nothing else to do that on Earth.”

The DAP structure is of long polymer chains containing double carbon bonds that break when severe strain and heat are applied, but not necessarily in the same configuration, but improves quickly when cooled.

“Think of a long polymer chain with dough as something like a bowl of ramen noodles soup,” says Sun, who worked on the project for his doctoral research, and is the first author of the paper. “You can stir it with chopsticks and then freeze it. Once you thaw the freeze, you can stir it and refreeze. It has the same ingredients as before and has a slightly different look.”

Currently Apple, Inc. Sang, an engineer at the company, said it’s not easy to perform ballistic tests on such a small scale until he came across a new research method called Lipit (Laser-induced Projectile Impact Test), which was recently developed by Thomas and colleagues at MIT.

Sang used Lipit to laser-fired a small silica projectile 3.7 micrometers in diameter from a glass slide covered in a thin gold film placed on a 1-square cure inch platform. His target consisted of a thin layer (75-435 nanometers) of super DAP.

An ultra-fast camera with 3 nanosecond exposure times at 50 nanosecond intervals recorded the action. The researchers then used scanning electron microscopes, laser scanning confocal microscopes, and infrared nanospectrometers to display holes and evaluate the covalent bonds of the superpolymer.

The results were initially confused, San said, as he could not find a hole in the target polymer.

“Did I not aim correctly? Were there any projectiles? What’s the problem with my experiment, I asked myself,” he said. However, when he placed the DAP sample under an infrared nanospectrometer that combines chemical analysis with advanced resolution, he was able to see the small perforations.

“It was actually a surprising and surprising discovery,” San said. “A very exciting discovery.”

He explained that this behavior cannot yet be reproduced at the macro level, as the strain rate during drilling of very thin target materials under impact is much higher than at the nanoscale.

“When this strain rate is really high, the material often has unexpected behaviors that people don’t normally see under normal circumstances,” San said. “With the Lipit device we use, we’re talking about strain rates in digits that are much higher than traditional scale bullets and targets. In that regard, the materials behave very differently.”

Another co-author of this paper is Hongkyu Eoh, a PhD student in Materials Science. Former postdoctoral researcher. Kailu Xiao, Wenpeng Shan, Jinho Hyon; Dr. Dmitry Kurouski, Associate Professor in the Department of Biochemistry and Biophysics, Texas A&M.

Sukhishvili and Thomas will continue their super DAP research using different polymer compositions, temperatures, and stress responses.

“You can even imagine designing a DAP with properties so that it can absorb kinetic energy by breaking the DAP. Some of these broken bonds are likely to have the correct “bond reform catalyst” present in the material, so that the material itself is going well before the material itself.

“To date, there is no material that has the time response required for deformation, destruction, reform, and deformation, destruction, reform during the sub-microsecond interval of ballistic events,” Thomas said.