THE BEHAVIOR OF CARBOPOL 980 IN AQUEOUS SOLUTIONS OF NONIONIC SURFACTANTS. II. EVIDENCE OF COMPLEX FORMATION BY ELECTRICAL CONDUCTIVITY, STEADY-STATE FLUORESCENCE, DYE SOLUBILIZATION AND TURBIDITY MEASUREMENTS

摘要

The effect of cross-linked PAA (Carbopol 980) on the micellization of two nonionic surfactants [polydisperse decaoxiethylene mono nonylphenyl ether (NPEO_(10)) and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock-copolymer (EO_(76)PO_(29)EO_(76), Pluronic F68, F68)] is investigated by electrical conductivity, static fluorescence, dye solubilization and turbidity. In the Carbopol-surfactant systems the conductivity decreases at a surfactant concentration below the critical micelle concentration (CMC), passes through a minimum and then increases. Static fluorescence indicates that the polymer-bound aggregates have similar micropolarity as the surfactant micelles, and the F68 aggregates bound to polymer are more hydrophobic than those of NPEO_(10). The Carbopol-F68 solubilizes higher amounts of oleophilic dye than the Carbopol-NPEO_(10) mixtures. Unlike the surfactant solutions, those containing Carbopol become turbid above a threshold surfactant concentration. These peculiarities demonstrate that Carbopol interacts with the investigated nonionic surfactants and the formed complexes are explained by the interplay between the hydrogen and the hydrophobic bondings.