(15c) Computational Study of Mechanochemical Activation in Nanostructured Triblock Copolymers

Mechanochemically active materials have emerged as an attractive platform for diverse applications in polymeric materials, including strain sensing, chemical catalysis, and self-healing properties. Understanding how bulk forces are transmitted on the molecular level is vital in the field of mechanochemistry in order to develop materials with targeted mechanochemical properties. Triblock ABA copolymers offer an attractive platform for controlling mechanochemical activation via their nanostructure. By measuring activation of a model spiropyran unit embedded in the middle of a triblock copolymer, we aim to determine the overall mechanophore activation its connection to the materials response to deformation. We find that mechanochemical activation during tensile deformation depends strongly on both the polymer composition and chain conformation in these materials, with activation requiring higher stress in materials with a higher glassy block content, and most activation occurring in the tie chains connecting different glassy domains and loop chains that are hooked onto each other. Additionally, we observe a spatial pattern of activation which appears to be tied to distortion of the self-assembled morphology. Higher activation is observed in the tips of the chevrons forming during deformation of lamellar samples, as well as in the centers between the cylinders in the cylindrical morphology. Our work shows that changes in the network topology significantly impact mechanochemical activation efficiencies in these materials, suggesting that this area will be a fruitful avenue for further experimental research.