Micellization of Diblock(oxyethylene/oxybutylene) Copolymer E11B8 in Aqueous Solution. Micelle Size and Shape. Drug Solubilization

Copolymer E 11 B 8 [E denotes OCH 2 CH 2, B denotes OCH 2 CH(C 2 H 5 ), and the subscripts denote number-average chain lengths] was prepared by sequential oxyanionic polymerization and characterized by GPC (for distribution width) and NMR spectroscopy (for absolute composition and chain length). It was studied as prepared with hydroxyl groups terminating the B-blocks (E 11 B 8 H) and after methylation (E 11 B 8 M). Clouding temperatures were determined over a wide concentration range, and critical micelle concentrations were determined by dye solubilization. Dynamic and static light scattering were used to characterize the micelles and demonstrate the formation of compact micelles at low temperatures which change to large (probably wormlike) micelles on heating the solution to temperatures within 10 °C of the clouding boundary. The solubilization of griseofulvin (a drug with poor water solubility) was determined over a range of temperature, and the effect of micelle size on this property is discussed.