Facile mechanochemical cycloreversion of polymer cross-linkers enhances tear resistance
Shu Wang, Yixin Hu, Tatiana B. Kouznetsova, Liel Sapir, Danyang Chen, Abraham Herzog‐Arbeitman, Jeremiah A. Johnson, Michael Rubinstein, Stephen L. Craig
Abstract
The mechanical properties of covalent polymer networks often arise from the permanent end-linking or cross-linking of polymer strands, and molecular linkers that break more easily would likely produce materials that require less energy to tear. We report that cyclobutane-based mechanophore cross-linkers that break through force-triggered cycloreversion lead to networks that are up to nine times as tough as conventional analogs. The response is attributed to a combination of long, strong primary polymer strands and cross-linker scission forces that are approximately fivefold smaller than control cross-linkers at the same timescales. The enhanced toughness comes without the hysteresis associated with noncovalent cross-linking, and it is observed in two different acrylate elastomers, in fatigue as well as constant displacement rate tension, and in a gel as well as elastomers.