Solubilization of phenols by intramolecular micelles formed by copolymers of maleic acid and olefins

The partition of a series of substituted phenols between water and polymer micelles formed by potassium salts of poly(maleic acid-co-1-olefins), PA-nK(2) with n ranging from 6 to 18, has been investigated. Steady-state and time-resolved fluorescence measurements have been used to study the formation and properties of these micelles. The data indicate that just PA-6K(2) exhibits a pH-induced conformational transition. All other copolymers adopt a compact configuration over the entire pH range. The hydrophobicity of these microdomains, as measured by the ratio III/I, increases with the length of the side alkyl chain. The aggregation number, i.e., the number of monomer units involved in the intramolecular micelle, has been found to be equal to the degree of polymerization, suggesting that one polymer chain forms one polymer micelle. The transfer free energies of p-alkyl-substituted phenols from water to PA-18K(2) and of phenol from water to PA-nK(2) have been measured. The contribution of each methylene group to the free energy is 0.97 and 0.34 kJ mol(-1) in the substituted phenol and the side alkyl chain, respectively. These values are lower than those determined for transfer of phenols to ionic micelles and to heptane.