Relationship between pluronic block copolymer structure, critical micellization concentration and partitioning coefficients of low molecular mass solutes

Using pyrene and homologous alkyl derivatives of fluorescein as fluorescent probes, this work examines the partitioning coefficients of hydrophobic so lutes in aqueous dispersions of Pluronic block copolymers (poly(ethylene ox ide)-block-poly(propylene oxide)-block-poly(ethylene oxide)). An incrementa l approach is developed, allowing measurement of the free energy of transfe r of a methylene group from aqueous media into the micelles. Effects of var iation of length of the ethylene oxide (EO) and the propylene oxide (PO) bl ocks in Pluronic molecules on the partitioning characteristics of the solut es are established. A simple reciprocal relationship between partitioning c oefficients of the solute and critical micellization concentration is demon strated.