Partition coefficient of araphiphilic hemicyanine dyes between the aqueousand the micellar phase of sodium dodecyl sulfate by differential absorbance spectroscopy

Solubilization in terms of hydrophobic interactions of amphiphilic hemicyan ine dyes by micelles of the anionic surfactant sodium dodecyl sulfate was s tudied. The critical micelle concentration was determined by a specific con ductivity method. The water-micelle partition coefficient (K-x) of these dy es was determined using a differential absorbance technique. The standard f ree energy change of solubilization (Delta G degrees(p)) and free energy ch ange per methylene group of the dyes, Delta G degrees(CH2) at 25 degrees C was also calculated. K-x, Delta G degrees(p), and Delta G degrees(CH2) were also calculated using both conductivity and differential absorbance data. Lengthening of the dialkyl chains of the hemicyanine dyes led to greater hy drophobic interaction and consequently enhanced solubility within micelles of sodium dodecyl sulfate. (C) 1998 Elsevier Science B.V. All rights reserv ed.