|(Credit: NYU Abu Dhabi)|
Self-healing polymers have been subject to chemists’ investigations for more than a decade and until now have only been observed in softer materials like rubber and plastic.
Pale yellow crystals the size of a baby’s fingernail—and about 0.5 mm thick—were grown in a lab by Patrick Commins, postdoctoral associate researcher at NYU Abu Dhabi and lead author of a paper in the journal Angwandte Chemie International Edition.
Commin says the research with dipyrazolethiuram disulfide crystals was inspired by the relationship between sulfur atoms in soft polymers, which tend to flow toward neighboring sulfur atoms and bond with them easily resulting in self-repair. He decided to test the same bond in crystals.
“What happens when we break the crystal is that we have all these sulfurs moving around and when we press them together they reform their bonds and they heal,” Commins explains.
Commins says the crystal was broken using a machine built specifically to hold tiny objects and that has the capability to break the object cleanly. The two halves of the broken crystal were mechanically brought into contact with each other at room temperature. Twenty-four hours later the crystal was whole again.
The only defect was a superficial mark left behind by the crack in the middle. The percentage of healing was 6.7 percent, which researchers calculated by comparing the amount of force required to break the crystal before and after the healing process.
Provided by New York University Written by Deepthi Unnikrishnan