Asymmetric star-branched block copolymers based on polystyrene (PS), polytetrahydrofuran (PTHF), and poly(methyl methacrylate) (PMMA) were synthesized by a combination of cationic ring opening polymerization and redox polymerization methods in two steps. At first, cationic ring opening polymerization of THF was initiated by using chain-end-multifunctionalized polystyrenes with 2, 4, and 8 benzyl bromide moieties as initiators in the presence of AgSbF6 at 30 degrees C to obtain 3-,5-, and 9-arm AB(2), AB(4), and AB(8), type asymmetric star-branched polymers consisting of PS (A) and PTHF-OH (B) segments. Polymers obtained in this way were characterized by gel permeation chromatography, FTIR, H-1 NMR, and thermal analysis (DSC and TGA). At second step, redox polymerization of methyl methacrylate was initiated by using these characterized asymmetric star-branched polymers as macroinitiators in the presence of Ce(IV) salt at 40 degrees C to obtain PS-s-(PTHF-b-PMMA)(n) (n = 2, 4, and 8) asymmetric star-branched block copolymers. PS-s-(PTHF-b-PMMA), (n = 2, 4, and 8) asymmetric star-branched block copolymers obtained were purified by fractional precipitation method before characterization. (c) 2006 Wiley Periodicals, Inc.