Direct synthesis of well-defined zwitterionic cyclodextrin polymers via atom transfer radical polymerization

A versatile atom transfer radical polymerization (ATRP) protocol was developed for the direct homo- and copolymerization of a sulfobetaine monomer, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium (SBMA), and a mono-functionalized beta-cyclodextrin (beta CD) methacrylate monomer. The polymers were characterized using 1- and 2D NMR spectroscopy and asymmetrical flow field-flow fractionation (AF4). Low dispersities (D-M = M-w/M-n) and high initiator efficiencies, of both the homo- and copolymers, indicated good control of the polymerization. The work thus represents one of the few reports where low D-M values are obtained for direct ATRP of SBMA and beta CD monomers. The novel beta CD copolymer showed salt-dependent upper critical solution temperature (UCST) behavior, while isothermal titration calorimetry revealed excellent binding properties.