Beckman Institute director Jeffrey Moore (left), postdoctoral researcher Hai Qian (center) and materials science and engineering head Nancy Sottos (right) led a team of Illinois engineers in the development of a new rapid-acting, reversible polymer that changes color when it is about to fail. Photo: L. Brian Stauffer.Materials that contain special polymer molecules may someday be able to warn us when they are about to fail. Engineers at the University of Illinois at Urbana-Champaign have improved their previously developed force-sensitive molecules, called mechanophores, to produce reversible, rapid and vibrant color change when a force is applied.
The new study, led by postdoctoral researcher Hai Qian, materials science and engineering professor Nancy Sottos and Beckman Institute of Advanced Science and Technology director Jeffrey Moore, is reported in a paper in Chem.
Moore's team has been working with mechanophores for more than a decade, but past efforts have produced molecules that were slow to react and then return to their original state, if at all. This inability to produce a rapid on/off-like response has limited the use of mechanophores as molecular probes for continuously reporting a material's mechanical condition.
"The color change is the result of stress applied to the bonds that connect the mechanophores to a polymer chain," Qian said. "We are now bonding the mechanophores to polymer chains using a different arrangement scheme, called an oxazine structure. The new structure allows for an instantaneous and reversible color change, so instead of the polymer slowly becoming darker over time, the color changes quickly when the force is applied and disappears when the force is removed."
Materials that contain the new mechanophores could be used as stress sensors to allow researchers to study the effects of stress on materials before they fail. "The rapid response and reversibility will allow engineers to better monitor, quickly detect and respond rapidly to an overstressed structure in the lab and eventually in the field," Sottos said.
A long-standing challenge in materials science has been making observations regarding mechanical load and other stresses in materials at the single-molecule level. Although this advance cannot do that, Moore says the development of this new type of mechanophore has brought the goal nearer.
"There is more work to do, but this advancement opens the door to detailed insight of what's going on at the molecular level in all sorts of materials," Moore said. "In the area of biomechanics, for example, we see this research as a steppingstone toward better monitoring of how our bodies react to external forces from the cellular level and beyond."
This story is adapted from material from the University of Illinois at Urbana-Champaign, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.