Four types of poly(vinyl alcohol-b-styrene-b-vinyl alcohol) (P(VA-b-S-b-VA)) triblock copolymers were synthesized by hydrolysis of poly(vinyl acetate-b-styrene-b-vinyl acetate) triblock copolymers prepared by radical living polymerization. The polyvinyl alcohol (PVA) core-polystyrene corona-type flower micelles were formed with ASA-4 in benzene at 25 degrees C. The PVA core part of the micelle was crosslinked with hexamethylene diisocyanate in solution. The monodispersed spherical products (microspheres) were synthesized by crosslinking.