Azobenzene/UV absorber dual-protected thermochromic elastomeric fibers toward enhanced light-resistance
Leuco dye-based thermochromic fibers suffer from poor light fastness, limiting their cyclability. Here, a hydrogen bond dissociation/structural isomerization-based dual ultraviolet (UV)-shielding strategy is proposed to develop enhanced light-resistant thermochromic elastomer fibers (Azo/TCM@Abs/TPU) employing UV absorbers and 4-dodecyloxyazobenzene (C12-Azo) through a coaxial wet-spinning process. The integration of UV absorbers and C12-Azo enhances UV protection, effectively blocking nearly the entire UV spectrum. The light fastness of Azo/TCM@Abs/TPU has been improved to Grades 3–4, enabling a stable thermochromic function to withstand several months of sunlight exposure. Additionally, the absorbed UV light is stored as chemical energy within C12-Azo via trans-to-cis photoisomerization. This stored energy can be released as heat on demand. The coaxial dual-protection concept using photoisomerization offers an efficient method to enhance light resistance in thermochromic fibers.