Micellization in water and adsorption onto solid particles of block copolymers

Abstract

Micelle formation and adsorption at the TiO 2–solution interface of a series of PS–PEO block copolymers in aqueous solutions was studied using fluorescence probing and small-angle X-ray methods. Further, the stability of aqueous TiO 2 dispersion in the presence of copolymers was investigated by microelectrophoresis, optical density and sedimentation measurements. The dissolution of pyrene as fluorescent probe in aqueous surfactant solutions leads to a slow decrease of the I 1/ I 3 ratio, as the copolymer concentration increases; I 1 and I 3 are respectively the intensities of the first and third vibronic peaks in the pyrene fluorescence emission. This behaviour was due to the characteristics of the copolymer and/or to the copolymer association efficiency in water. Moreover, the adsorption at the plateau level increases with decreasing PEO chain length. The zeta potential of TiO 2 particles decreases with increasing copolymer concentration and reaches a plateau value. Finally, stabilization using block copolymers was more effective with samples having higher weight fractions of PS block.