An ε-caprolactone-derived 2-oxazoline inimer for the synthesis of graft copolymers

An inimer approach is presented here for the formation of bottlebrush copolymers consisting of a poly(2-oxazoline) backbone and acrylate branches. A hydroxyl group containing 2-oxazoline (2-n-pentanol-2-oxazoline) was synthesized from ε-caprolactone, which is a sustainable starting material. 2-n-Pentanol-2-oxazoline was then further functionalized with a bromoisobutyrate group, which was used to initiate a Cu(0)-mediated reversible-deactivation radical polymerisation (RDRP) of acrylates. This compound is termed an “inimer” because it contains both a monomer (2-oxazoline) and an initiator (the RDRP initiator in this study). Herein, we report the use of an inimer to form 2-oxazoline-based polymer backbones through cationic ring opening polymerisation, and further polymerisation via the Cu(0)-mediated RDRP of acrylates was achieved by initiating from the RDRP-initiator sites embedded within the poly(2-oxazoline) backbone. Furthermore, statistical copolymers of 2-ethyl 2-oxazoline and the inimer were also formed leading to statistically distributed radical initiating sites, which were then used to form graft copolymers of varying densities.