Synthesis of well-defined branched copolymers by quaternization of near-monodisperse homopolymers

We report the synthesis of water-soluble cationic branched copolymers by quaternization of near-monodisperse poly [2-dimethylamino)ethyl methacrylate] chains using bis(2-iodoethoxy)ethane. This model system is very useful for exploring the relative propensities for intermolecular branching and intramolecular cyclization. At polymer concentrations higher than the critical overlap concentration (c*), intermolecular branching is preferred over intramolecular cyclization; however, below c*, intramolecular cyclization is much more likely than intermolecular branching. These results allow some rationalization of the apparently contradictory literature data on branched copolymers prepared by living radical copolymerizations.