Atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) process, and the conventional radical polymerization (RP) were applied to the copolymerization of methyl methacrylate (MMA) and methacrylate-terminated poly(dimethylsiloxane) macromonomer (PDMS-MA). They resulted in PMMA-g-PDMS graft copolymers with various branching and molecular weight distributions. By applying appropriate conditions, ATRP led to homogeneously branched copolymer and RAFT to gradient branched copolymer. The RP process gave heterogeneously branched copolymer with large polydispersity. The structure and mechanical properties in these copolymers were analyzed.