Synergistic and visualized toughening of elastomers through mechanophore crosslinks and multiple networks

Abstract

Elastomers are essential in applications requiring high extensibility, yet their performance can be further enhanced through innovative design. A molecular design using multiple interpenetrating networks, where a brittle first network is isotropically prestretched by swelling in a stretchable matrix, dramatically increases toughness, primarily due to stress delocalization through bond scission in the sacrificial first network. In this work, we present a synergistic approach to elastomer design by employing anthracene–maleimide mechanophores as weak crosslinks in the first network of a multiple network elastomer. The interplay between mechanophores and multiple network structures not only improves the toughness but also enhances the mechanophore activity, achieving up to 37% activation in the triple network elastomer. The mechanofluorescence enables real-time visualization of bond scission, providing mechanistic insights into the toughening mechanism. Fluorescence imaging reveals significant mechanophore scission near the fracture surfaces of double and triple network elastomers. Mechanical and optical analyses indicate that the first network bears the majority of the load and that the mechanophore scission quantitatively correlates with the work of the fracture. This work demonstrates how mechanophores as weak crosslinks combined with multiple network topology synergistically enhance toughness and enable stress visualization, paving the way for damage-reporting, self-sensing elastomers with superior mechanical resilience.