A versatile synthetic route to macromonomers via RAFT polymerization

We describe a facile route to prepare functional macromonomers using reversible addition-fragmentation chain transfer (RAFT) polymerization. This was demonstrated in the synthesis of alpha-functionalized norbornenyl, vinyl, and cinnamyl macromonomers using functional chain transfer agents bearing these end groups. Various homopolymer macromonomers of well-controlled molecular weights were synthesized with near-quantitative incorporation of the end group functionality. The use of norbornenyl and vinyl CTA's resulted in a highly quantitative polymerization of styrene and methyl methacrylate (MMA) monomers yielding well-defined linear macromonomers. On the other hand, monomers with a lower reactivity such as methyl acrylate (MA) exhibited a broader polydispersity. The cinnamyl-functionalized telechelics proved the most challenging due to a competitive chain transfer between the cinnamyl group and the RAFT CTA at higher conversions. To demonstrate utilization of the macromonomer functionality, we synthesized the poly(norbornene-g-PMMA) copolymer based on the ring-opening metathesis polymerization (ROMP) of the norbornenyl-functionalized PMMA macromonomer. The main advantage of this new approach should be in the ability to prepare a variety of macromonomer structures utilizing the mild and tolerant conditions of RAFT polymerization.