The effect of hydrophobe chemical structure and chain length on the solubilization of griseofulvin in aqueous micellar solutions of block copoly(oxyalkylene)s

Abstract

The solubilization capacities of micellar solutions of a series of block copolymers composed of hydrophilic poly(oxyethylene) (E) and hydrophobic poly(oxypropylene) (P), poly(oxybutylene) (B) or poly(oxyphenylethylene) (S, from styrene oxide) have been compared using the poorly water-soluble drug griseofulvin as a model solubilizate. A ¹H NMR technique for determining the extent of solubilization has been developed. Considering the optimum result in each case, the amount of griseofulvin solubilized (expressed as moles griseofulvin per mole of hydrophobic units) by ES block copolymers was approximately nine times more than by EP copolymers and three times more than by EB copolymers. The mobility of the S-blocks in the cores of the ES copolymer micelles, as determined by ¹H NMR spectroscopy, was sufficient to allow solubilization at ambient temperature.