High‐Strength, High‐Barrier Bio‐Based Polyester Nanocomposite Films by Binary Multiscale Boron Nitride Nanosheets

Abstract Owing to the inferior dispersibility of boron nitride nanosheets (BNNSs) and weak interfacial interaction with the matrix, the performance of BNNS‐based composites is usually far below theoretically predicted values. Here, binary multiscale BNNSs (LDH‐BNNSs) fillers are synthesized through in situ growth of layered double hydroxide (LDH) on the BNNSs’ surfaces. LDH‐BNNSs with a multiple mosaic interface show superior dispersion of nanosheets in matrix and extraordinary filler‐matrix bonding. Density functional theory simulations reveal the stable dispersion mechanism of LDH‐BNNSs. Moreover, the bio‐based poly(ethylene furandicarboxylate) composites with 0.2 wt% LDH‐BNNSs loading exhibit simultaneous improvements in tensile strength (≈140 MPa), Young's modulus (≈6.5 GPa), toughness (≈2.0 MJ m⁻³), and gas barrier properties. Regulation of the interfacial structures of binary multiscale BNNSs significantly increases the filler utilization of the nanosheets, leading to extraordinary stress transfer efficiency and a physical shielding effect. Therefore, this simple, efficient, and novel strategy has promised in enhancing composite performance, and it provides a novel way to develop strong, tough, and high‐barrier bio‐based polyester composites.