Quantitative Mechanochemistry: A Chemical Tool to Bridge Polymer Physics and Mechanics of Soft Polymer Networks

In recent years, mechanochemistry has imposed itself as a novel promising chemical tool to bridge the gap between polymer physics and continuum mechanics in soft materials. The suitable incorporation of force-sensitive molecules (mechanophores) in load-bearing positions in soft (entropic) polymer networks and in linear chains has provided a tool to detect stresses and bond scission in 2D and 3D through the intensity of an optical signal. We review recent results linking the optical signal detected upon mechanophore activation with the applied mechanical load. Recent investigations have addressed critical questions, such as detecting and quantifying stress fields and measuring quantitative damage by bond scission in diverse cases, including failure in uniaxial tension, crack propagation in continuous loading, cyclic fatigue, or crack initiation in uniaxial and triaxial tension. We also discuss the requirements to go from simple imaging to quantitative detection, enabling comparisons between different materials and the calibration of continuum mechanics models. In ideal cases, the optical signal provides highly sensitive information on the size and intensity of damage zones in front of cracks-regions that would otherwise be undetectable.