Highly Stretchable and Tunable Thermo-fluorochromic Polymer Elastomer Through Eu3+ Dynamic Coordination Cross-linking

Thermochromic polymers with tunable thermochromism, high stretchability and mechanical strength are of interests for optical information storage and encryption. In this work, we demonstrate a new design of thermo-fluorochromic carboxylated nitrile butadiene rubber (XNBR) elastomer cross-linked by Eu³⁺-COOH dynamic coordination with deprotonated imidazole (DPIm) as the ancillary ligand. The presence of DPIm not only improves the mechanical strength and stretchability, but also dramatically intensifies the fluorescence emission and lifetime of the Eu-containing elastomer. The elastomer behaves reversible thermo-fluorochromism with easily tunable transition temperature and emission intensity by the simple change of the deprotonation degree of imidazole. The facile tunable thermo-fluorochromism, exceptional mechanical strength, and high stretchability (up to about 5000%) enable the Eu-containing XNBR elastomer with potential applications in soft electronics where optical information storage and encryption are required.