SOLUBILIZATION EQUILIBRIA OF ALCOHOLS AND POLYMERS IN MICELLAR SOLUTIONS - NMR PARAMAGNETIC RELAXATION STUDIES

The solubilization equilibria of some typical alcohols in cationic, anionic, and nonionic surfactant micellar solutions were investigated using the NMR paramagnetic relaxation method [J. Phys. Chem., 93 (1989) 2190]. The degree of solubilization of solubilizate in the micellar phase, p, was determined by monitoring the change in the 1H spin-lattice relaxation rate of the solubilizate upon the addition of paramagnetic ions to the aqueous phase. Hydrophilic paramagnetic ions, which should have the same sign of charge as the micellar surface for the case of ionic surfactant systems, were used to enhance the spin-lattice relaxation rate of solubulizate in the aqueous phase. The degree of solubilization obtained is, within experimental error, independent of the concentration of the paramagnetic ions. The error in the degree of solubilization, p, decreases with increasing paramagnetic ion concentration. The results obtained using different paramagnetic ions (i.e., 3-carboxylate-PROXYL (charge: - 1) and Mn (EDTA)2- in anionic micellar systems, and Mn (D2O)2+6 and Mn (EDTA)2- in nonionic micellar systems) are in good agreement. The paramagnetic relaxation method was also used to determine the degree of solubilization of poly (ethylene oxide) in two surfactant solutions, sodium ω-phenyldecanoate and sodium dodecyl sulfate. © 1990.