Partitioning of Pyrene between “Crew Cut” Block Copolymer Micelles and H2O/DMF Solvent Mixtures

The effect of solvent composition on the partition coefficient ( K V ) of pyrene between the crew cut micelles formed from highly asymmetric block copolymers of polystyrene (500)- b -polyacrylic acid (60) and an H 2 O/DMF solvent mixture was studied using a fluorescence method. The total number of pyrene molecules incorporated per micelle was also determined as a function of polymer concentration and solvent composition. The relationship between the partition coefficient ( K V ) and the mass equilibrium constant ( K ) was obtained, and the free energy of transfer of pyrene from the solvent mixture to the micelle was calculated in terms of K . The results suggest that a gradual change in the solvent composition, which makes it increasingly incompatible with the solubilizate, may be a good method of loading hydrophobic materials into micelles.