Relationship between the molecular structure, molecular polarities and dyeing properties of benzisothiazole dyes containing multi-ester groups for PET fabric

The disperse dyes with high fastness are very important for polyethylene terephthalate (PET) fabric dyeing and printing. The esterified groups of the dye molecules directly affect the wet fastness of dyes. In this paper, a series of azo disperse dyes containing different ester groups based on benzisothiazole were designed and synthesized. Their chemical structures were characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance techniques (H-1 NMR) and elemental analysis. The dyeing performances of the dyes containing different esters for polyester fabric were discussed. The optimized geometries, the bond lengths, dipole moment, lattice dimensions and the electrostatic potential energy diagram of the dyes were calculated and simulated using DFT method at B3LYP/6-31G (d) level. The relationship between the structure and dyeing properties of benzisothiazole dyes containing multi-ester groups for PET fabrics was investigated. The effects of the different ester groups in the dye molecules on the dyeing rate and wet fastness were analyzed. The disperse dyes containing ester group exhibited deeper and brighter intense blue hues than that of the non-ester one. Different ester groups had obvious effect on the dyeing rate of the dyes on PET fabric. The dye structure with two longer ester groups has better wet fastness. The results are of great significance to the development of the disperse dyes with high fastness. (C) 2019 Elsevier B.V. All rights reserved.