Micelle formation of poly[styrene-b-(4-vinylphenol)] diblock was studied in a 80/20 water/dimethyl sulfoxide (H2O/DMSO) solvent mixture using fluorescence spectroscopy with pyrene as the probe. The ratio of first and third emission peaks of pyrene changed significantly as micellar aggregation occurred upon increasing the copolymer concentration. Micellization occurred at ca. 13.8 mg/liter in this solvent mixture. (C) 1994 Academic Press, Inc.