Tough and Photoluminescent Diblock Copolymer Elastomers via Lanthanide Coordination

Thermoplastic elastomers (TPEs) of poly(methyl methacrylate)-block-poly(n-butyl acrylate-co-vinyl imidazole) (PMMA-b-P(BA-co-VI)) diblock copolymers have been synthesized as a model system to demonstrate supramolecular photoluminescence (PL) TPEs via lanthanide coordination. Europium ion (Eu³⁺) with a red PL and terbium ion (Tb³⁺) with a green PL have been selected as the lanthanide ions to coordinate the imidazole groups of the soft block. Upon microphase separation, hard PMMA blocks form spherical domains in the continuous matrices of the soft P(BA-co-VI) phase. At a volume fraction of 0.29, PMMA hard sphere domains act as a physical network in the matrix. Upon incorporating lanthanide ions, the soft P(BA-co-VI) matrix is cross-linked through metal coordination to form a second physical network. Synergistic interaction and reinforcement of local segmental coordination network and global glassy particle percolation network greatly enhance both the tensile strength and toughness of TPEs without compromising the stretchability. Moreover, the PL spectrum of TPEs can be continuously tuned by varying the composition and molar ratio of Eu³⁺/Tb³⁺.