Quantitative stress and damage mapping in multiple network elastomers using a single mechanophore.

Abstract

Recently developed scissile mechanochemical probes provide powerful tools for direct visualization of the stress and damage behaviors of polymeric materials. However, simultaneous mapping of both stress and damage fields using a single mechanophore remains challenging. While widely used reversible ring-opening mechanophores (e.g., spiropyran and rhodamine derivatives) effectively report stress levels, they poorly correlate with microscopic damage evolution. In this study, we demonstrate that rhodamine-based mechanophores embedded in multiple network elastomers can simultaneously map both stress distribution and network damage. Although initial loading-induced damage does not immediately alter fluorescence responses, accumulated damage manifests as delayed activation and diminished intensity upon reloading to the same strain. During deformation, mechanophores undergo ring-opening, generating fluorescence, while the crosslinked network sustains progressive damage. While ruptured chains contribute to fluorescence during the initial cycle, their mechanophores remain inactive upon reloading. Consequently, comparative fluorescence analysis across cyclic loading enables simultaneous stress mapping in the first cycle and damage quantification through the difference between cycles. Building on this mechanism, we develop a mechanochemical damage model that accurately captures both stress-strain behavior and fluorescence evolution under diverse loading conditions. By integrating experiments and simulations, we achieve stress and damage visualization in tough elastomers under both homogeneous and inhomogeneous deformations.