Reversible Ratiometric Mechanochromic Fluorescence Switching in Highly Stretchable Polyurethane Elastomers with Ultratoughness Enhanced by Polyrotaxane
Trang Manh Khang, Rong Huang, Amir Khan, Wei‐Tsung Chuang, Pham Quoc Nhien, Tu Thi Kim Cuc, Bùi Thị Bửu Huê, Kung‐Hwa Wei, Yaw‐Kuen Li, Hong‐Cheu Lin
Abstract
Multistimuli-responsive polymers containing mechanophoric motifs are highlighted as promising mechano-luminescent materials upon stretching via optical fluorescence signals. Herein, we report a distinct ratiometric force-induced fluorescence changes from green-emissive napthalimide stopper (donor) embedded in polyrotaxane (PR) cross-linkers to red-emissive rhodamine mechanophore (acceptor) incorporated in polyurethane (PU) backbones. The utilization of PR (1 wt %) can significantly enhance both toughness and stretchability in our targeted PU elastomers, where the mechanical work is largely dissipated by the ring-sliding motion and pulley effects of PR cross-linkers during stretching. Therefore, the simple soft robotic behavior with ultrafast shape memory and reversible ratiometric mechanochromic fluorescence switching by heating (60 °C) in PR-based PU films provide a distinctive strategy for the construction of molecular machines in the high-performance elastomers, which also offer pathways for practical applications of stimuli-responsive polymers in highly stretchable artificial muscles featuring both outstanding pulley effects on enhanced mechanical properties and novel signal variations of mechanochromic fluorescence simultaneously.