Monitoring the Stress-Activated Region in Hydrogen-Bonded Supramolecular Polymer Networks

Abstract

To explore the evolution of the stress-activated region in supramolecular network polymers, we incorporate aggregation-induced quenching moieties into macromolecular chains. Upon cutting the material, a significant increase in the fluorescence intensity is observed around the cut region, signaling the formation of a stress-activated region. This fluorescence enhancement is attributed to the dissociation of hydrogen bonds, which increases the free-volume fraction, as revealed by positron annihilation lifetime spectroscopy. As the cut section anneals, the fluorescence intensity, width, and free-volume fraction of the stress-activated region gradually decrease, indicating repair of the network structure. Notably, the repair process begins at the bulk side and progresses toward the cut section. The rate of this repair process can be quantified by monitoring the reduction in the region width. Furthermore, the evolution of the stress-activated region is strongly influenced by the density of hydrogen bonds, which govern molecular mobility. These findings offer valuable insights into the molecular dynamics of supramolecular interactions and guide the rational design of advanced supramolecular network polymers.