The Effect of Morphology on Mechanical Activation in Nanostructured Triblock Copolymers

Mechanochemistry has emerged as an attractive approach for driving constructive chemical transformations in responsive polymeric materials. However, understanding how the polymer structure influences the molecular force distribution in bulk materials under mechanical load remains a challenge. Here, we investigate the effect of polymer morphology on mechanochemical activation in nanostructured triblock copolymers. We synthesize a series of force-responsive block copolymers (PMMA-b-PnBA-SP-PnBA-b-PMMA) containing a force-sensitive spiropyran unit at the center of the rubbery midblock, with varying lengths of the glassy end-blocks to achieve different well-ordered morphologies. We compare the mechanochemical activation behaviors of the polymers using simultaneous tensile tests and optical measurements, and show that the mechanochemical activation is strongly correlated to the chemical composition and morphologies of the block copolymers, with increasing glassy block content driving activation of the mechanophore at lower strain. These findings demonstrate that self-assembly of nanostructured morphologies is a viable route to controlling mechanochemical activation in polymeric materials, and provide insights into how such nanostructuring impacts molecular-scale force distributions in these materials.