Mechanically Robust and Healable Bromobutyl Rubber Ionomer via Designing the Resonance Isomerization Effect

Abstract

Integrating mechanical robustness with efficient healability under mild conditions is an inevitable requirement for the commercial development of self-healing ionomers. This work reveals that the resonance isomerization effect can be adopted to construct vigorous ionic networks in ionomers. As a proof of concept, 4-(alkylamino) pyridine (DMAP) and its derivatives are selected to react with bromobutyl rubber (BIIR) to fabricate BIIR ionomers. The ionized DMAP moieties manifest a resonance isomerization effect, leading to stronger ionic interactions, larger regular ionic aggregations, and more obvious microphase separation. Benefiting from the resonance isomerization effect, the BIIR ionomers in our work possess superior tensile strength (21 MPa) and toughness (92 MJ/m3), exceeding those of the existing BIIR-based materials. Moreover, the plasticizing effect of the alkyl substituent group on the DMAP-based derivatives can be further used to tailor the ionic cluster relaxation, thereby overcoming the compromise between mechanical performance and self-healing ability. Despite the dynamic network, the self-healing BIIR ionomers show a high gas barrier property which is very close to that of covalently crosslinked BIIR, enabling their potential to be used in next-generation repairable automobile tires. This work will expand the toolbox of ionic bond chemistry and afford an effective molecular design approach for optimizing mechanical and self-healing properties simultaneously.