The aim of this study was to define a block copolymer micellar system with a high solubilization capacity for poorly soluble aromatic drugs. Ethylene oxide and phenyl glycidyl ether were sequentially polymerized to form the diblock copolymer G5E67 (G = phenyl glycidyl ether, OCH 2CH(CH2OC6H5); E = oxyethylene, OCH2CH2; subscripts denote number-average block lengths in repeat units). The association properties in aqueous solution over the range 20-50 °C were investigated by surface tensiometry and light scattering, yielding values of the cmc, hydrodynamic radius, and association number; gel boundaries in concentrated micellar solution were investigated by tube inversion. The solubilization capacity of G5E67 for the poorly water-soluble drug griseofulvin was higher than that of a triblock EGE copolymer of longer G block length and considerably higher than that achieved with poloxamers (EmPnEm, P = oxypropylene). © 2006 American Chemical Society.