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

Abstract

The synthesis, polymerization, and copolymerization of a new cyclic ester, y-(2-bromo-2methyl propionyl)-e-caprolactone (3), containing a pendent-activated alkyl bromide functional group is described. This new compound serves as both a monomer for "living"ring-opening polymerization (ROP) as well as an initiator for the controlled atom transfer radical polymerization (ATRP). Three distinctive routes to poly(e-caprolaetone)-graft-poly(methyl methacrylate) copolymers were surveyed by either sequential or concurrent living polymerization procedures. The first approach involves the ROP of e-caprolactone with various compositions of 3, followed by the polymerization of methyl methacrylate via ATRP from the activated alkyl bromide sites along the polyester backbone. Alternatively, a-lactone functional methyl methacrylate macromonomers were prepared by ATRP of methyl methacrylate initiated from 3. The macromonomers were copolymerized with e-caprolactone 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 e-caprolactone, 3, and methyl methacrylate together with the appropriate initiator for the ROP and the catalyst for the ATRP. The new monomer enabled new graft copolymers having an aliphatic polyester backbone with poly(methyl methacrylate) grafts of controlled molecular weight and narrow polydispersities (~1.3). © 1999 American Chemical Society.