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Ultraviolet-visible spectra of Orange II exhibit blue shifts in apolar solvents due to the formation of the azo tautomer. Upon absorption to cotton, Orange If remains as the hydrazone tautomer and, like other phenylazonaphthol dyes or Methyl Orange, exhibits small red spectral shifts Two superimposed spectra -- characteristic of the azo and hydrazone tautomeric forms - are detected when dye 1 (X = p-MeO) absorbs onto cotton Only the azo form is observed on nylon; all other dyes, except Orange II, give blue shifts. A model is developed in which the more apolar moiety of the dye binds to pockets formed in the non-crystalline (amorphous) regions of cotton, with those parts containing the sulphonate group protruding into aqueous pores. In nylon, the binding sites are more apolar with the sulphonate groups bound electrostatically. [ABSTRACT FROM AUTHOR]

A wide-ranging investigation has been made of the adsorption of direct dyes to cotton and of inhibition by surfactants, polymers and polymer-surfactant mixtures. Generally, the selected polymers are extremely effective at inhibiting adsorption of most of the direct dyes to cotton but are less effective at inhibiting adsorption of small, model azo dyes. Micellar solutions of zwitterionic and cationic surfactants can inhibit adsorption of both small dyes and commercial dyes. It is shown that anionic surfactants at sub-micellar concentrations can inhibit polymer-dye interactions due to displacement of dye and/or relocation into micelle-like polymer-surfactant complexes. New insights have been obtained into the interactions of dyes with cotton and with polymers, surfactants or their mixtures, particularly into observed dye selectivities. [ABSTRACT FROM AUTHOR]

A spectroscopic study (UV-vis and adsorption) has been made of the interactions of select model azo dyes with a range of surfactant types or their mixtures both above and below their respective critical micelle concentrations. All surfactants inhibit adsorption of the dyes to cotton above their critical micelle concentrations due to incorporation in micelles. However, formation of 1:1 complexes between dyes and cationic or zwitterionic surfactants in sub-micellar regions results in enhanced deposition on cotton. It is shown that attractive or repulsive electrostatic interactions play a key role in dye binding to micelles. Unusually, spectra of complexes formed between the dye and cationic surfactant are typical of those of the azo tautomeric form as opposed to the hydrazone form that is prevalent in aqueous media. Addition of anionic surfactant to micellar solutions of nonionic or zwitterionic surfactants results in successive displacement of dye from the respective micelles, i.e. binding is competitive. [ABSTRACT FROM AUTHOR]

Presents a study which assessed the key factors that control the transfer of dyes between garments during detergency. Materials used in the experiments; Methodology; Adsorption of dyes to cotton at pH 10; Influence of polymers upon adsorption to cotton at pH 10; Influence of anionic surfactants on polymer efficacy; Conclusions.