Crosslinker-Mediated Compatibilization Mechanisms in Dynamic Polymer Networks

Dynamic covalent networks are a class of crosslinked polymers capable of undergoing reversible bond exchange reactions, enabling structural reorganization without loss of overall network integrity. When such dynamic bonds are employed to compatibilize immiscible polymer blends, two key factors become particularly important: (i) their influence on the bulk polymer density, and (ii) the interfacial activity of the crosslinking groups. To elucidate these effects, we perform molecular simulation of both bulk polymer melts and thin polymer films containing explicit small-molecule crosslinkers. Our simulations reveal that the bulk density and spatial distribution of dynamic bonds within the polymer matrix are strongly governed by the crosslinker size and their chemical affinity with the host polymer. Specifically, when the crosslinkers are chemically compatible with the polymer matrix, the overall packing fraction increases irrespective of crosslinker size. In contrast, incompatible crosslinkers reduce the packing fraction and preferentially segregate toward the polymer–air interface, resulting in a decrease in interfacial tension. These findings suggest that chemically incompatible crosslinkers can promote both miscibility and interfacial compatibility in polymer blends by forming copolymer-like structures at the interface. Overall, the study highlights the critical role of crosslinker–polymer interactions and crosslinker size in dictating the structural and interfacial properties of dynamic covalent networks.