Interactions between new multi-anionic surfactants and direct dyes and their effects on the dyeing of cotton fabrics

A series of novel surfactants containing multi-anionic and nonionic hydrophilic moieties have been prepared by reacting fumaric acid with polyoxyethylenated stearyl ether in the presence of a peroxy-type free radical initiator to form addition products featuring a carboxylic acid groups. The critical micelle concentration (CMC) decreased upon increasing the length of the polyoxyethylene chain of the surfactant. The surface excess concentration at the surface and the occupied area per surfactant molecule were calculated. We used spectrophotometric methods to study the interactions between the dyes and the polycarboxylated multi-anionic surfactants. The rate of direct dyeing of cotton was influenced by the degree of aggregation of the dye in the dye bath. Indeed, disaggregation of direct dyes in the presence of the surfactants increased the rate of dye uptake by the cotton fibers. On the other hand, the formation of dye–surfactant complexes retarded the rate of dye uptake on the cotton fabrics.