The reactivity ratios of methyl methacrylate (MMA) and methacryloyl-terminated poly-(dimethylsiloxane) macromonomer (PDMS-MA) were determined in four different systems, using either conventional radical copolymerization or atom transfer radical copolymerization (ATRP) and using low molecular weight initiators or poly(dimethylsiloxane) macroinitiators. While the relative reactivity of PDMS-MA (1/r MMA) decreased to 0.3-0.4 in the conventional radical polymerization, the reactivity ratio was higher in ATRP systems (ca. 0.8). The use of macroinitiator in the ATRP system increased 1/rMMA at high concentration and helped regularly incorporate PDMS-MA into the copolymer. However, in the conventional radical polymerization or redox systems, macro(azo)initiator did not as significantly improve the reactivity ratio of PDMS-MA. Graft copolymers obtained by ATRP (in both solution and semibulk) have much lower polydispersities than obtained in conventional radical systems.

Atom transfer radical copolymerization of methyl methacrylate (MMA) and (meth)acrylateterminated poly(lactic acid) (PLA) macromonomers was investigated. The relative reactivity of methacrylate-terminated macromonomer (1/r MMA ) 1.75) and acrylate-terminated macromonomer (1/rMMA ) 0.61) was close to that of 2-hydroxyethyl methacrylate and 2-hydroxyethyl acrylate, respectively. The difference in reactivity in ATRP and conventional radical polymerization is discussed in terms of the diffusion control effect. A mixture of methacrylate-terminated macromonomer and acrylate-terminated macromonomer was copolymerized with MMA by ATRP to give a homogeneously branched PMMA-g-PLA graft copolymer with low polydispersity (M w/Mn ) 1.15).

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.

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