Search for: All records

Abstract Force‐responsive molecules that produce fluorescent moieties under stress provide a means for stress‐sensing and material damage assessment. In this work, we report a mechanophore based on Diels‐Alder adductTAD‐Anof 4,4′‐(4,4′‐diphenylmethylene)‐bis‐(1,2,4‐triazoline‐3,5‐dione) and initiator‐substituted anthracene that can undergo retro‐Diels‐Alder (rDA) reaction by pulsed ultrasonication and compressive activation in bulk materials. The influence of having C−N versus C−C bonds at the sites of bond scission is elucidated by comparing the relative mechanical strength ofTAD‐Anto another Diels‐Alder adductMAL‐Anobtained from maleimide and anthracene. The susceptibility to undergo rDa reaction correlates well with bond energy, such that C−N bond containingTAD‐Andegrades faster C−C bond containingMAL‐Anbecause C−N bond is weaker than C−C bond. Specifically, the results from polymer degradation kinetics under pulsed ultrasonication shows that polymer containingTAD‐Anhas a rate constant of 1.59×10⁻⁵ min⁻¹, whileMAL‐An(C−C bond) has a rate constant of 1.40×10⁻⁵ min⁻¹. Incorporation ofTAD‐Anin a crosslinked polymer network demonstrates the feasibility to utilizeTAD‐Anas an alternative force‐responsive probe to visualize mechanical damage where fluorescence can be “turned‐on” due to force‐accelerated retro‐Diels‐Alder reaction.