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.

Study of the Morphology and Mechanical Properties of Vulcanized Rubber Functionalized with Sodium Phosphate Esters

“…The associations of ionic compounds covalently bonded to organic polymers, generally dubbed ionomers, can be tuned via the strength of the dipole moment in ion pairs or the grafting density of the dipoles. Ionomers have been widely studied and commercialized as thermoplastics − and thermoplastic elastomers, − but less attention has been given to the reinforcement of thermoset elastomers by ionic association − and related transition metal–ligand association . The sparsity is at least partly attributable to the difficulty in processing ionically functionalized rubber prior to vulcanization.…”

Ionic crosslinked polypropylene-based thermoplastic elastomers with excellent mechanical properties

“…[31][32][33][34][35][36][37][38] The ionic groups aggregated to form strong physical cross-linkers in the polymer matrix, which promoted the elastic behaviour of the material, improving its strength, toughness, and wear resistance. [39][40][41][42][43][44][45][46][47] Valentin et al reported an ionic elastomer, which exhibited a tensile strength of 40 MPa and an elastic recovery of approximately 90%. 48 Nie et al designed a dynamic dual-cross-linked network strategy for fabricating an ionic elastomer, which showed excellent mechanical properties with a high toughness (33.8 MJ m −3 ) and favorable elasticity (>85%).…”