Thermodynamics of the solubilization of water-insoluble dyes by complexes of cationic surfactants with poly(vinyl sulfate) of different charge densities

yThe solubilization of two water-insoluble dyes, o-(2-amino-1-naphthylazo)t oluene (OY) and 1-pyrene-calbaldehyde (PyA), by complexes of anionic polyel ectrolyte and alkyltrimethylammonium bromide (C-12-TAB, C(14)TAB, C(16)TAB) was examined using sodium poly(vinyl sulfate) (PVS) with different charge densities at 298.2 K. The change in the Gibbs function was estimated for th is solubilization equilibrium. These complexes showed a larger solubilizing capacity for OY than for PyA. Their capacity for OY was larger than that o f the corresponding surfactant micelles. The charge density of PVS influenc ed the solubilizing capacity in C(12)TAB and C(14)TAB solutions but had lit tle effect in C(16)TAB solutions. PVS with a 40% charge density had the low est solubilizing capacity. Bound short-chain surfactants are expected to ha ve a smaller lateral interaction with neighboring surfactants bound to PVS with a lower charge density, thus forming a less hydrophobic complex with a lower solubilization capacity. The observed weak solubilization by PVS wit h a low charge density was ascribed to this less hydrophobic complex.