Constructing Dynamic Interfacial Crosslinks in Poly(Styrene‐ <scp> <i>b</i> </scp> ‐Isoprene‐ <scp> <i>b</i> </scp> ‐Styrene)/Boehmite Composites for Gas Barrier Applications

ABSTRACT Thermoplastic elastomers (TPEs), combining room‐temperature elasticity and thermoplasticity at elevated temperatures, represent a promising solution to the recycling challenges of conventional crosslinked rubbers. Despite the widespread use of styrenic TPEs, their gas barrier properties remain insufficiently explored, even though such characteristics significantly influence service performance and reliability. Herein, an interfacial crosslinking strategy is developed for poly(styrene‐ b ‐isoprene‐ b ‐styrene) (SIS) elastomers reinforced with boehmite (BM) nanoplatelets. Through thermal compression, β‐hydroxy phosphate ester bonds can be established between epoxidized SIS and phytic acid‐modified BM, enabling dynamic interfacial linkages that improve filler dispersion and interfacial strength. The resulting crosslinked composite exhibits distinctly enhanced tensile strength and modulus (from 1.37 to 2.80 MPa) relative to the uncrosslinked counterpart due to efficient stress transfer. Strikingly, the crosslinked composite shows an 84% decline in nitrogen permeability relative to pristine SIS (from 3.0 × 10 −17 to 4.9 × 10 −18 m 3 ·m/(m 2 ·s·Pa)), primarily attributed to the diminished free volume and the suppression of continuous gas diffusion pathways. Benefiting from the dynamic nature of the interfacial bonds, the crosslinked composite maintains good reprocessability, accompanied by desirable thermal stability. Overall, the proposed interfacial crosslinking strategy imparts the composite with outstanding gas barrier property and mechanical robustness, while preserving recyclability and thermal stability, thereby enabling wider utilization of the SIS‐based composites.