High Gas Barrier\nElastomer/Boehmite Composites with\nMechanical Robustness and Improved Flame Retardance Enabled by Segregated\nStructure with Interfacial Dynamic Cross-Links

High gas barrier rubber composites are crucial for the\napplications\nrequiring the combination of high resilience and gas impermeability.\nLayered fillers are commonly used to enhance the gas barrier performance\nby reducing free volume and creating tortuous gas diffusion paths.\nHowever, it remains challenging to strengthen interfacial interactions\nand manipulate filler distribution, which significantly affect free\nvolume and gas diffusion paths. Herein, we present a facile strategy\nto build a segregated structure in modified rubber composites with\ndynamic interfacial cross-linking toward mechanically robust, high\ngas barrier elastomer composites. Concretely, boehmite (BM) nanoplatelets\nmodified with biobased phytic acid (PA) are utilized to cross-link\nepoxidized natural rubber (ENR), forming dynamic β-hydroxy phosphate\nester cross-links for strong interfacial interaction. This system\nallows a segregated structure to be readily established by hot pressing\nthe compounds containing ENR gum, PA-modified BM, precross-linked\nENR granules and zinc acetate. The volume exclusion effect of ENR\ngranules drives the selective dispersion of BM, generating a two-phase\nsegregated structure with the bridged interfaces across phases formed\nvia bond exchange of dynamic cross-links. This results in excellent\ngas barrier performance along with distinctly improved mechanical\nproperties. Notably, the N<sub>2</sub> permeability of the segregated\ncomposites is reduced by 90% to 4.23 × 10<sup>–19</sup> m<sup>3</sup>·m/(m<sup>2</sup>·s·Pa) compared to\nneat ENR. Additionally, improved fire safety is achieved benefiting\nfrom the combined effects of PA, BM, and the segregated structure.\nThis work offers a promising and scalable approach for fabricating\nhigh-performance elastomer composites that combine outstanding gas\nbarrier properties, mechanical durability and flame retardance, making\nthem suitable for a wide range of demanding applications.