Urea-containing azo disperse dyes: Synthesis, application, and structure-property relationship for nylon fabrics

A group of new disperse dyes containing urea groups was synthesized by coupling various diazonium salt with urea-containing coupling components, which were prepared by the reaction between N-(2-Aminoethyl)-N-ethyl3-methylbenzenamine and p-toluene isocyanate. Then, the structures of the synthesized dyes were characterized by H-1 NMR,C- 13 NMR, FTIR, and MS analysis. The spectral characteristics of the dimethylformamide (DMF) solution and applied properties on the nylon fabric for all of the new dyes were assessed and compared with the amino-containing control dye. Correlations between molecular structure and dyeing properties on nylon fabric for the urea-containing dyes were investigated by using density functional theory (DFT). The results indicated that the dyeing rates of the dyes became slower, and the fastness properties on the nylon fibers, including washing, sublimation, and light, were greatly improved after the introduction of the p-toluenpiride group. The color performance, build-up, and light fastness properties of the urea-containing dyes varied with the diazo components, among which 4-nitroaniline and its cyano substituted analogues performed well. Both dye exhaustion and saturation adsorption on the nylon fabric were negatively correlated with the product (F2.F6) of the dipole moment of the dye (F2) and its molecular weight (F6). In addition, the ClogP value had a significant negative correlation with the washing change fastness, and the dipole moment of the dye was positively correlated with the sublimation change fastness. Also, the dyes with larger molecular volume and molecular weight had lower rates of sublimation changes and wet crocking fastness due to surface adsorption on the nylon fibers.