Synthesis of a Novel Disperse Reactive Dye Involving a Versatile Bridge Group for the Sustainable Coloration of Natural Fibers in Supercritical Carbon Dioxide

Disperse reactive dyes with appropriate chemical structure are key for the coloration of natural fibers in the water-free environmentally friendly medium of supercritical carbon dioxide with various advantages. The objective of this work is to design and synthesize a novel anthraquinonoid disperse reactive dye involving a versatile bridge group to improve the coloration properties of the dye in supercritical carbon dioxide. Cross-coupling condensation based on an Ullmann reaction between N-phenylethylenediamine and 1-chloroanthraquinone in a ligand-free system is investigated by optimizing the synthesis parameters. Notable influences are observed from the dosages of N,N-dimethyl formamide and potassium hydroxide, as well as the system temperature and reaction duration, on the isolated yield of the dye precursor. An optimized process is also recommended for synthesizing the designed novel dye. Then, the chemical structure, color characteristics, and coloration properties of the obtained dye are further investigated and successfully characterized by utilizing Fourier-transform infrared analysis,H- 1 and C-13 nuclear magnetic resonance spectroscopy, UV-vis absorption spectroscopy, elemental analysis, and liquid chromatography-mass spectrometry. Additionally, practical coloration experiments are performed with cotton, silk, and wool in a supercritical carbon dioxide medium.