Cationic polymerization of styrene (S) was performed with peroxy initiators synthesized from bis(4,4'-bromomethyl benzoyl peroxide) (BBP) or bromomethyl benzoyl t-butyl peroxy ester (t-BuBP) and AgSbF6 or ZnCl2 system at 0 and -10 degrees C to obtain macromonomeric peroxy initiators (poly-S initiators). Kinetic studies were accomplished for poly-S initiators. Poly(styrene-block-methyl methacrylate) block copolymers [poly(S-b-MMA)] were synthesized by bulk polymerization of methyl methacrylate (MMA) with poly-S initiators. The quantum chemical calculations for the initiating systems of the cationic polymerization of S and poly(S-b-MMA) block copolymers were achieved using Hyperchem 7.5 program. The optimized geometries of the polymers were investigated with the quantum chemical calculations. Poly(S-b-MMA) block copolymers containing undecomposed peroxide groups were used to initiate thermal copolymerization of acrylic acid (AA) to obtain crosslinked poly(S-b-MMA-b-AA) multicomponent copolymers. The crosslinked multicomponent copolymers were investigated by sol-gel analysis. Swelling ratio values of the crosslinked multicomponent copolymers in CHCl3 were calculated. Poly-S initiators having undecomposed peroxygen groups were used for graft copolymerization of polybutaclien (PBd) to obtain crosslinked poly(S-graft-polybutadien) graft copolymers [poly(S-g-PBd)]. The characterizations of the polymers were achieved by FTIR, H-1-NMR, GPC, SEM, and DSC techniques. (c) 2006 Wiley Periodicals, Inc.