Photochromic functionalization of polyetheramine-cured epoxy resin based on spiropyran derivatives doping

Despite being a widely used polymer material, studies on the spiropyran (SP)-derived photochromic functionalization of amine-cured epoxy resin materials are not sufficiently detailed. Traditional amine-based curing agents can undergo chromogenic reactions with SP through multiple reaction mechanisms. Furthermore, the dense crosslinked network structure of the resin restricts the conformational isomerization of SP, thereby leading to the failure of photochromic functionalization in epoxy resin systems. In this work, a SP derivative (YBSP), which contains a meta-dinitrobenzene structure, was synthesized and doped into polyetheramine-cured epoxy resin materials. Polyetheramine does not react with SP to form small molecular fragments, and the bulky side group of YBSP provides sufficient free volume for its isomerization in the resin crosslinking structure. As a result, the resin material doped with YBSP exhibits photochromic properties after exposure to 365 nm UV light, and as the YBSP content increases, the fracture toughness of the resin is enhanced, with its fracture strength reaching 72.815 MPa. In conclusion, doping YBSP into epoxy resin not only imparts photochromic functionality to the material but also enhances its toughness while maintaining its original thermodynamic properties.