Facile synthesis of cyclic RAFT agents and ring expansion radical polymerization of vinyl monomers having cyclic topology

Abstract

In this paper, we describe the synthesis of cyclic vinyl polymers by ring-expansion radical polymerization using a cyclic RAFT agent, which is prepared by bimolecular ring-closing esterification of succinic acid and bis{4-[ethyl-(2-hydroxyethyl)carbamoyl]benzyl} trithiocarbonate using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide·HCl (EDC) and 4-(dimethylamino)pyridine (DMAP) as the condensation agents. We demonstrated ring-expansion polymerization of n-butyl acrylate mediated by the cyclic RAFT agent under light irradiation. Bulk polymerization also occurs to afford the corresponding cyclic polyacrylate. The cyclic topology was confirmed by matrix assisted time laser desorption/ionization (MALDI)-time of flight (TOF) mass spectroscopy and transmission electron microscopy (TEM).