Synergistically Tailoring Mechanical and Optical Properties of Diblock Copolymer Thermoplastic Elastomers via Lanthanide Coordination

Diblock copolymer thermoplastic elastomers (TPEs) of poly(methyl methacrylate)-block-poly(n-butyl acrylate-random-vinylimidazole) [PMMA-b-P(BA-r-VI)] have been designed and synthesized as a model system for demonstrating simultaneously tailoring photoluminescence (PL) and mechanical properties of TPEs via lanthanide coordination. Europium ions with red PL and terbium ions with green PL have been incorporated in TPEs to coordinate imidazole groups on soft blocks. PL spectra can be continuously tuned by varying both the overall ion composition and their relative portions. The rubber elasticity of TPEs arises from entropic restoring of entangled coil chains in the soft matrix filled with glassy PMMA microdomains as physical cross-links. Upon incorporating lanthanide ions, a second network forms due to the lanthanide coordination cross-linkages among soft P(BA-r-VI) chains. Synergistic interactions and reinforcement of local and global networks greatly enhance both the tensile strength and toughness of TPEs without compromising the stretchability and elasticity. In situ small-angle X-ray scattering reveals deformation and relaxation of microstructures upon cyclic uniaxial stretching and recovery. The novel strategy in the design and synthesis of TPEs with tunable optical and mechanical properties enables a wide range of smart materials and technologies.