Microphase-Controlled Chain Relaxation in Dynamic Covalent Networks

Dynamic covalent networks (DCNs) represent a class of polymers in which specific monomeric units- called stickers-form reversible covalent crosslinks that enable network rearrangement without compromising overall connectivity. While the primary role of these crosslinking moieties is to maintain network integrity, an equally important yet less appreciated aspect is their chemical dissimilarity from the backbone monomers. Such heterogeneity, particularly in terms of polarizability and chemical affinity, can induce microphase separation, giving rise to hierarchical nano and microstructures within the network. However, the molecular mechanisms governing chain relaxation in microphase-separated DCNs remain poorly understood. In this work, we employ a hybrid molecular dynamics–Monte Carlo simulation framework to investigate the relaxation dynamics of a microphase-separated DCNs. Contrary to the conventional understanding that the chain relaxation is governed primarily by the intrinsic dynamics of sticker exchange, our results reveal that relaxation is instead dominated by the slow exchange of stickers between adjacent microphases. This inter-microphase sticker migration emerges as the rate-determining step controlling the viscoelastic behavior of the network. Our findings offer a powerful strategy to tailor the relaxation and mechanical properties of DCNs-providing fundamental insights for designing reprocessable, adaptive materials relevant to the emerging polymer economy.