Design and Synthesis of Mechano‐Responsive Color‐Changing Thermoplastic Elastomer Based on Poly(n‐Butyl Acrylate)–Spiropyran‐Polystyrene Comb‐Structured Graft Copolymers

Abstract Colorimetric mechanophores like spiropyran (SP) represent an emerging type of interesting signal molecule that can be incorporated into polymers or other materials as a stress transducer. In this work, a new type of spiropyran‐containing inimer molecule MA‐SP‐Br are designed and synthesized, which is incorporated into polybutylacrylate (PBA) chains through reversible addition‐fragmentation chain transfer (RAFT) copolymerization with n‐ butyl acrylate (BA). PBA‐SP‐Br is then used as a macro‐initiator to graft polystyrene (PS) side chains from the PBA backbone through atom transfer radical polymerization (ATRP) of styrene. The resulting comb‐structured graft copolymer PBA‐SP‐PS contains 0.15–0.34% SP and exhibits a characteristic feature of thermoplastic elastomers. Under uniaxial stretch, the materials possess an excellent mechano‐responsivity and change color at strains as low as about 14%.