Photo‐Activated Nano‐Compatibilized Two‐Phase Polymer Blends: Dynamics of Morphology‐Mechanics Coupling

Light‐activated polymers (LAPs) are shape‐shifting materials capable of transforming their shapes in response to photoinduced chemical reactions, such as cis‐trans isomerization and dimerization. Owing to these reactions, LAPs often exhibit behavior analogous to multicomponent, multiphase polymer blends, where phase separation and interfacial effects play a critical role in governing mechanical performance. In this work, we present a free‐energy‐based theoretical framework to predict the time‐dependent mechanical response of nanoparticle (NP)‐compatibilized elastic LAP blends undergoing phase‐separation. In particular, we capture the effect of photo‐chemical reactions on morphology, demonstrating that reaction rates can be tuned to control the domain size and, consequently, the stress distribution under external deformation. Furthermore, we show that enhanced NP‐induced compatibilization reduces the average stress within the material by promoting more uniform and finely dispersed domains, leading to improved stress transfer across interfaces. Our framework is readily adaptable to other complex systems, including high‐entropy polymers and thermo‐responsive or light‐activated systems, with potential applications in soft robotics, biomedical devices, micromechanics, 4D printing, and material origami. Additionally, the model can be integrated with physics‐informed neural networks for the analysis of complex domain geometries and enable comprehensive parametric studies.