Jessica Clough will present a seminar Molecularly Resolved Imaging of Deformation and Damage in Polymeric Materials

Polymeric materials deform and fail through highly heterogeneous processes that are difficult to resolve from bulk mechanical measurements alone. Local stress concentrations, stress redistribution, molecular rearrangements, and the onset of damage often occur around defects, interfaces, inclusions, and other structural heterogeneities, long before macroscopic failure. Understanding these processes requires experimental approaches that can connect macroscopic mechanics with local molecular response.

In this talk, I will show how molecular force probes, or mechanophores, can be used as optical reporters of deformation and damage in polymeric materials. Using fluorescent supramolecular mechanophores that respond to relatively small molecular forces, we mapped heterogeneous deformation around defects, inclusions, and regions of concentrated stress in both elastomeric and glassy polymer matrices.[1],[2] These experiments produced quantitative fluorescence-based strain maps that reveal how local deformation fields deviate from the macroscopically applied load.

To probe the chemical consequences of these stress and strain concentrations, we developed a coumarin-based mechanophore that undergoes a force-induced chemical transformation to generate a fluorescent coumarin dye.[3] This platform allows permanent molecular damage to be mapped optically, while also offering control over both the activation threshold and the photophysical properties of the reporter. It therefore provides a route to visualising where and when molecular-level bond scission occurs during material deformation and failure.

Looking ahead, we are developing next-generation mechanophores that combine force sensitivity with photoswitchable or lifetime-based optical readouts. These systems aim to detect earlier and more localised stages of damage, and to extend molecular-scale force mapping towards nanoscale and time-resolved imaging of deformation processes in polymer systems.

Together, these strategies permit molecularly resolved optical mapping of how polymeric materials deform and fail. By revealing where deformation is concentrated, when damage begins, and how molecular events lead to macroscopic failure, they can help guide the design of longer-lived, more reliable polymeric materials.