The impact of steric groups on the dyeing properties of indophenine dyes
Polyester fabrics are usually dyed with disperse dyes.However,as the dye and fiber are bonded by van der Waals force and hydrogen bond,the affinity is weak.During the finishing process,thermal migration of dyed polyester fabrics may occur if the temperature is high.In such case,the dye molecule will migrate from the inside to the surface of the fiber,resulting in unlevelness and poor color fastness of the dyed fabrics.The use of dyes with a planar molecular structure can enhance the affinity between the dye and the fiber and effectively alleviate the heat migration phenomenon.Indophenine is composed of quinoidal bithiophene structure that is end-capped with two indole-2-one groups.The molecular π-conjugation system of indophenine presents planar characteristic.In addition,indophenine is usually synthesized by indophenine reaction,which is easy to operate and has high product yield.Previously,our team discussed the dyeing properties of hydrophobic indophenine dyes on polyester fibers.The results showed that the dye-fiber interaction force between indophenine dye molecules and polyester fibers is very strong.Nevertheless,due to the existence of strong intermolecular force which hinders the formation of single-molecule-state dyes,the dye exhaustion of indophenine dyes on polyester fabrics is not high enough.In this paper,three blue dyes D1—D3 were synthesized through indophenine reaction.The structures of dyes D1—D3 were characterized by mass and infrared spectra.The lattice parameters and HOMO/LUMO energy level information of dyes D1—D3 were calculated.The thermal stability,acid and alkali stability and absorption characteristics in DMF of dyes were tested and analyzed.Polyester fabrics were dyed with dyes D1—D3 by high-temperature and high-pressure dyeing method.The dyeing process was optimized,and the dye uptakes,color depths,color fastnesses and migration values of the dyed fabrics were tested.The results show that the optimized dyeing condition should be at pH of 5-6,dyeing temperature of 130℃and dyeing bath ratio of 1:50.Under the optimum dyeing condition,the dye uptakes are 84.8%(D1),97.5%(D2)and 85.2%(D3),respectively and the K/S values of dyed polyester fabrics are 17.1(D1),8.1(D2)and 16.3(D3),respectively.The fabrics dyed with dyes D1—D3 have excellent thermal migration resistance,and the migration values are less than 10%,which are obviously better than that of the conventional disperse dye C.I.disperse blue 56.In addition,the color fastnesses to soaping,rubbing and sublimation of polyester fabrics dyed with dyes D1—D3 are excellent,and all of them are above 4-5.The introduction of methoxy or methyl groups on the thiophene unit can effectively tune the intermolecular forces between the dye molecules,promote the formation of single-molecule-state dyes in the dye bath,and thus improve the dyeing performance of the indophenine dyes.
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