Solubilization of Water-Insoluble Dyes by Polyion/Surfactant Complexes

Abstract

Abstract Solubilization data for the water-insoluble dyes o-(2-amino-1-naphthylazo)toluene (OY) and 1-pyrenecarbaldehyde (PyA) in mixed solutions of anionic polyelectrolyte and a cationic surfactant are reported. The polymers used were sodium dextran sulfate (DxS) and the sodium salt of poly(styrenesulfonic acid) (PSS). The surfactants used were dodecyltrimethylammonium bromide (DTAB) and tetradecyltrimethylammonium bromide (TTAB). DxS exhibited a highly cooperative binding of the surfactant ions, while binding to PSS occured at lower surfactant concentrations, but was less cooperative. DxS/surfactant complexes had a larger solubilization capacity per bound surfactant ion for both OY and PyA than did PSS/surfactant complexes. The standard Gibbs energy changes for solubilization in DxS/DTAB were determined to be 4.0 kJ mol−1 for OY and 5.4 kJ mol−1 for PyA; the values in PSS/DTAB were 6.5 kJ mol−1 for OY and 9.3 kJ mol−1 for PyA. The solubilization capacities and standard Gibbs energy changes of polyion/surfactant complexes strongly relate to the binding mode of the surfactant. The differences in the solubilization capacities and standard Gibbs energy changes between polyion/surfactant complexes and DTAB or TTAB micelles, and between OY and PyA, are discussed in relation to the aggregate size and solubilizate location.