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

Integrating mechanical robustness with efficient healabilityundermild conditions is an inevitable requirement for the commercial developmentof self-healing ionomers. This work reveals that the resonance isomerizationeffect can be adopted to construct vigorous ionic networks in ionomers.As a proof of concept, 4-(alkylamino) pyridine (DMAP) and its derivativesare selected to react with bromobutyl rubber (BIIR) to fabricate BIIRionomers. The ionized DMAP moieties manifest a resonance isomerizationeffect, leading to stronger ionic interactions, larger regular ionicaggregations, and more obvious microphase separation. Benefiting fromthe resonance isomerization effect, the BIIR ionomers in our workpossess superior tensile strength (21 MPa) and toughness (92 MJ/m(3)), exceeding those of the existing BIIR-based materials. Moreover,the plasticizing effect of the alkyl substituent group on the DMAP-basedderivatives can be further used to tailor the ionic cluster relaxation,thereby overcoming the compromise between mechanical performance andself-healing ability. Despite the dynamic network, the self-healingBIIR ionomers show a high gas barrier property which is very closeto that of covalently crosslinked BIIR, enabling their potential tobe used in next-generation repairable automobile tires. This workwill expand the toolbox of ionic bond chemistry and afford an effectivemolecular design approach for optimizing mechanical and self-healingproperties simultaneously.