Cyclic Ketene Acetals (CKAs), Old Monomers with New Features

Y. Du, S. Lazzari, M. Bergeler, M. Pfeifle, Y. Du, E.B. Coughlin

Keywords: cyclic ketene acetals, radical ring-opening polymerization


Since the first report on the radical ring-opening polymerization (rROP) of cyclic ketene acetals (CKAs) by William J. Bailey, et al. in 1980s, this monomer family has been extensively studied to develop a convenient approach for polyester syntheses with a radical based chain-growth pathway. In addition to the ring-opening capability to enable ester insertion and bring sustainable development opportunities for conventional radical based polymeric portfolios, CKAs possess unique characteristics which inspire the preparation of novel copolymer structures. The ring-opening of CKAs leads to the formation of radicals with significantly different reactivities, such as a primary alkyl radical species versus a benzyl radical, from 5,6-benzo-2-methylene-1,3-dioxepane and 2-methylene-1,3,6-trioxocane, respectively. Using polyethylene oxide (PEO) as the solvent enables the facile preparation of PEO graft copolymers. A variety of graft copolymer architectures can be obtained based on different radical reaction kinetics and thermodynamics of CKAs. Tailoring these CKA copolymer compositions could bring selectivity for enzymatic or microorganism biodegradability, moving towards the goal of greater sustainability in material end-of-life fate.