Enhanced gas barrier properties of brominated butyl rubber nanocomposites embedded with orientation <scp>Al₂O₃</scp>@<scp>PDA</scp>‐<scp>Fe₃O₄</scp> nanoplatelets by a magnetic field

Abstract The strategic alignment of nanoplatelets within polymer matrices is pivotal for the development of nanocomposites with superior gas barrier characteristics. In this work, the effect of lamellar particles orientation in polymer for gas permeation was demonstrated. The magnetic α‐Al 2 O 3 (Al 2 O 3 @PDA‐Fe 3 O 4 ) was first prepared by in situ growth of Fe 3 O 4 nanoparticles immobilized on polydopamine (PDA)‐modified Al 2 O 3 surface. Subsequently the orientation of magnetic α‐Al 2 O 3 in brominated butyl rubber (BIIR) was achieved by modulating the applied magnetic field direction. Results show that the PDA, as the role of surface adhesive, not only anchored Al 2 O 3 substrate but also bound ferric ions for the further in situ formation of Fe 3 O 4 , which ensured the physico‐chemical stability of the magnetic α‐Al 2 O 3 . Comparison of hydrogen permeation performance of composites with in‐plan, middle‐of plane and out‐of plane alignment demonstrated the effect of lamellar particles orientation. The Al 2 O 3 @PDA‐Fe 3 O 4 /BIIR composite with in‐plane alignment had the best hydrogen barrier property by a 50% reduction in hydrogen permeability coefficient compared to the neat BIIR, underscoring the critical role of particle orientation in enhancing the gas barrier properties of nanocomposites. Highlights The structural stability of magnetic Al 2 O 3 nanocomposites was enhanced by polydopamine (PDA). The composites with in‐plane alignment, middle‐of plane alignment and out‐of plane alignment were prepared by a magnetic field. The effect of lamellar particles orientation on gas permeation of polymer nanocomposites was studied. The composites with in‐plane alignment possesses the best gas barrier property.