Salt-free neutral dyeing of cotton fiber with monochlorotriazine type reactive dyes

In this paper, we present the modification of cotton with glycidyltrimethylammonium chloride (GTA), demonstrating its capability not only for salt-free dye adsorption but also for achieving fixation reactions with monochlorotriazine-type reactive dyes under neutral conditions. The results of adsorption kinetics and isotherm experiments indicate that the adsorption of reactive dyes by modified cotton is chemisorption. Color-stripping experiments conducted on modified cotton dyed with different dyes revealed that GTA-modified cotton underwent fixation reactions with monochlorotriazine-type reactive dyes under neutral conditions. The reaction sites of modified cotton with reactive dyes were determined by measuring the 1 H NMR of the model reaction products. Mechanism investigation using Density Functional Theory (DFT) on the fixation reaction revealed that the hydroxyl groups on the modification agent chain exhibit a lower pKa value and carry more negative charge, resulting in a lower reaction barrier with monochlorotriazine-type reactive dyes. Our research findings demonstrate that GTA-modified cotton fiber enhance the reactivity of cotton, providing significant guidance for the development of novel modifiers.