Solubilization of phenols in surfactant/polyelectrolyte systems

The properties of the microheterogeneous systems formed by mixtures of cetyltrimethylammonium bromide (CTAB) and an alternating copolymer of maleic acid and styrene, MAS, and their anionic monoesters, MAS-n with n = 2, 4, 6, 8, were investigated. The fluorescence of pyrene was used to sense the polarity of the polymer/CTAB aggregates. Measurements of the ratio III/I in pyrene fluorescence spectra indicate that the polymer/CTAB aggregates are more hydrophobic than normal micelles. A series of p-alkyl substituted phenols were employed to probe the solubilization ability of these aggregates. The distribution constant K-S of phenol, p-methylphenol, p-ethylphenol, and p-propylphenol between water and MAS-n/CTAB aggregates and the corresponding free energy of transfer Alto have been determined using the pseudo-phase model. The results show that the distribution is mainly determined by the phenol structure, and a linear free energy relationship has been fpund between Deltamu(t)(0) and the structure of the phenols. On the other hand, an increase in the number of methylene groups in the side alkyl chain has no effect on Deltamu(t)(0). The results are discussed and compared with those obtained for ionic micelles. (C) 2003 Elsevier Inc. All rights reserved.