Toward understanding the cross‐linking from molecular chains to aggregates by engineering terminals of supramolecular hyperbranched polysiloxane

Crosslinking thermosets with hyperbranched polymers confers them superior comprehensive performance. However, it still remains a further understanding of polymer crosslinking from the molecular chains to the role of aggregates. In this study, three hyperbranched polysiloxane structures (HBPSi‐R) are synthesized as model macromolecules, each featuring distinct terminal groups (R denotes amino, epoxy, and vinyl groups) while similar molecular backbone (Si‐O‐C). These structures were subsequently copolymerized with epoxy monomers to construct interpenetrating HBPSi‐R/epoxy/anhydride co‐polymer systems. The spatial molecular configuration and flexible Si‐O‐C branches of HBPSi‐R endow them with remarkable reinforcement and toughening effects. Notably, an optimum impact strength of 28.9 kJ mol−1 is achieved with a mere 3% loading of HBPSi‐V, nearly three times that of the native epoxy (12.9 kJ mol−1). By contrasting the terminal effects, the aggregation states and crosslinking modes were proposed, thus clarifying the supramolecular‐dominant aggregation mechanism and covalent‐dominant dispersion mechanism, which influences the resulting material properties. This work underscores the significance of aggregate science in comprehending polymer crosslinking and provides theoretical insights for tailoring material properties at a refined molecular level in the field of polymer science.