Facile mechanochemical cycloreversion of polymer cross-linkers enhances tear resistance

S Wang and YX Hu and TB Kouznetsova and L Sapir and D Chen and A Herzog- Arbeitman and JA Johnson and M Rubinstein and SL Craig, SCIENCE, 380, 1248-1252 (2023).

DOI: 10.1126/science.adg3229

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.

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