En Route To Polymer That Heals Upon Squeezing

Researchers at the University of Illinois, Urbana-Champaign, have taken a first step toward making a material that responds directly to being damaged (J. Am. Chem. Soc., DOI: 10.1021/ja305645x). Self-healing polymers have been synthesized in the past, but many of those materials use encapsulated reagents or require external stimuli, such as light or heat, to initiate repair. To make the material, the Illinois researchers generated what they call a “mechanophore” from a gem-dichlorocyclopropanated indene flanked by two methacrylate groups. The team then polymerized this mechanophore with methyl acrylate. When squeezed hard enough to simulate pressures above what a roadway bridge might withstand, the mechanophores in the resulting polymeric material rearrange and release protons (shown). Team leader Jeffrey S. Moore says that the next step will be to couple these mechanophores with a polymer that can also undergo acid-catalyzed cross-linking. That way, he adds, the protons generated will initiate localized healing of the material “only in regions of high-stress concentration, where cross-linking is needed most.”