Synthesis of fluorescent cationic coumarin dyes with rigid molecular structures to improve lightfastness and their related modacrylic dyed fibers

In this study, three novel cationic, fluorescent, coumarin dyes (6a, 6b and 6c) with rigid molecular structures were synthesized and characterized by spectroscopic studies. The photochemical behavior (UV light) of these dyes was studied in ethanol and DMF solvents. Compared to that of a commercial dye (basic yellow-40), the synthesized dyes exhibited good photostability in these solvents. A dyeing experiment was performed on modacrylic fibers with these dyes using a traditional cationic dyeing process. The effect of pH on the absorption spectra and dye bath exhaustion were also studied. The dyeing results showed that all the dyes exhibited obvious fluorescence effects. Based on the luminance factor (β), and photostability behavior, the synthesized dyes can hopefully be applied in high-visibility, fluorescent, yellow warning textiles with improved lightfastness.