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

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