Reprocessable Supramolecular Thermoplastic BAB-Type Triblock Copolymer Elastomers with Enhanced Tensile Strength and Toughness via Metal–Ligand Coordination

A new strategy was proposed to enhance tensile strength, toughness, and extensibility of BAB-type reprocessable supramolecular triblock copolymer elastomers (STBCPEs) by simply incorporating 1-vinylimidazole (VI) as a minor comonomer to introduce metal–ligand coordinate bonds of minor contents into the soft matrix. Poly(n-butyl acrylate-co-1-vinylimidazole)-b-poly(isobornyl acrylate)-b-poly(n-butyl acrylate-co-1-vinylimidazole) (P(BA-co-VI)-b-PIBA-b-P(BA-co-VI)) triblock copolymers with varied molecular masses were synthesized via successive reversible addition–fragmentation chain transfer (RAFT) polymerization. Zinc chloride (ZnCl2) was used to coordinate with the pendent imidazole groups in the soft matrix. These supramolecular STBCPEs exhibited simultaneously improved creep-resistance, Young's modulus, tensile strength, and toughness without sacrificing any extensibility. Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) results indicated that these supramolecular elastomers showed typical microphase-separated morphology. The microstructure of elastomeric STBCPEs consisted of microphase-separated glassy PIBA domains, serving as physical cross-linking points for one network, and metal–ligand cross-linked clusters formed by ZnCl2 and imidazole groups, which constrained the soft flexible end P(BA-co-VI) blocks, serving as cross-linking points for the second network. This strategy provides a novel means to design high-performance reprocessable supramolecular elastomers through strategically introducing a network of dynamic metal–ligand interaction into the microphase-separated thermoplastic elastomeric system.