Unimolecular combination of an atom transfer radical polymerization initiator and a lactone monomer as a route to new graft copolymers

The synthesis, polymerization, and copolymerization of a new cyclic ester, gamma-(2-bromo-2-methyl propionyl)-epsilon-caprolactone (3), containing a p endent-activated alkyl bromide functional group is described. This new comp ound serves as both a monomer for "living'' ring-opening polymerization (RO P) as well as an initiator for the controlled atom transfer radical polymer ization (ATRP). Three distinctive routes to poly(epsilon-caprolactone)-graf t-poly(methyl methacrylate) copolymers were surveyed by either sequential o r concurrent living polymerization procedures. The first approach involves the ROP of epsilon-caprolactone with various compositions of 3, followed by the polymerization of methyl methacrylate via ATRP from the activated alky l bromide sites along the polyester backbone. Alternatively, alpha-lactone functional methyl methacrylate macromonomers were prepared by ATRP of methy l methacrylate initiated from 3. The macromonomers were copolymerized with epsilon-caprolaetone via ROP to form the target graft copolymers. Finally, the graft copolymers could be prepared in a simple one-step approach by the concurrent polymerization of epsilon-caprolactone, 3, and methyl methacryl ate together with the appropriate initiator for the ROP and the catalyst fo r the ATRP. The new monomer enabled new graft copolymers having an aliphati c polyester backbone with poly(methyl methacrylate) grafts of controlled mo lecular weight and narrow polydispersities (similar to 1.3).