Disperse Dyeing of Nylon with Spironaphthoxazines and the Evaluation of the Photochromic Performance Using a Novel Photochromic Assessment Methodology

Herein, two spironaphthoxazine-based photochromic dyes are synthesized and their dyeing, fastness, and photochromic properties on nylon fabric are investigated. A novel performance indicator, the photochromic efficiency index (PEI), is proposed to assess the photochromic performance of the synthesized spironaphthoxazine dyes. Using the PEI, the parameters affecting dyeability and photochromic performance are optimized for efficient photochromic performance, and a pH of 9 and temperature range of 80–90 °C are determined as the optimal dyeing conditions. Evidently, 1,4-diazabicyclo [2.2.2]octane improves photocoloration efficiency by inhibiting thermal oxidative degradation via singlet oxygen quenching. The dye containing a hydroxyl group achieves higher buildup and photochromic performance on the nylon fabric owing to its increased affinity in terms of polarity and hydrophilicity. The synthesized dyes exhibit reasonable buildup and photocoloration properties on nylon fabric, in addition to excellent color fastness to washing, rubbing, and perspiration.