Hyperbranched Epoxy/Silica Hybrid Networks for Strong and Moisture‐Resistant Wood Polymer Composites

Fast‐growing poplar is a renewable hierarchical porous material; however, its low mechanical strength, poor toughness, and high moisture affinity limit its application in structural fields. In this work, a hyperbranched epoxy resin/modified silica sol hybrid system was developed as an organic–inorganic reinforcing phase and introduced into poplar wood via vacuum‐pressure impregnation. An in situ hybrid network was constructed within the cell walls and lumens through epoxy ring‐opening reactions, Si‐O‐Si inorganic condensation, Si‐O‐C covalent bonding, and interfacial interactions with wood hydroxyl groups. The synergistic combination of flexible hyperbranched epoxy segments and rigid silica frameworks improved interfacial compatibility, pore filling, and stress transfer within the wood‐based composite. Consequently, the modified wood exhibited an impact toughness of 73.75 kJ/m 2 and a modulus of rupture of 150.43 MPa, representing increases of 50.51% and 110.6%, respectively, compared with the control material (49 kJ/m 2 and 71.43 MPa, respectively). Meanwhile, the water contact angle increased significantly from 82.3° to 125.5°, indicating reduced moisture affinity and improved hydrophobicity. This work provides an effective organic–inorganic hybrid network strategy for developing high‐performance wood‐based polymer composites with improved mechanical performance and environmental stability.