Multifunctional Fe(III)-Binding Polyethers from Hydroxamic Acid-Based Epoxide Monomers.

Multiple hydroxamic acids are introduced at poly(ethylene glycol) (PEG) via copolymerization of ethylene oxide with a novel epoxide monomer containing a 1,4,2-dioxazole-protected hydroxamic acid (HAAGE). AB- and ABA-type di- and triblock copolymers as well as statistical copolymers of HAAGE and ethylene oxide are prepared in a molecular weight range between 2600 and 12 000 g mol with low dispersities (Ð < 1.2). Cleavage of the acetal protecting group after the polymerization is achieved by mild acidic treatment, releasing multiple free hydroxamic acids tethered to the polyether backbone. The chelation properties of different polymer architectures (statistical versus diblock and ABA triblock) are investigated and compared with regard to the number and position of hydroxamic acids. Separation of the hydroxamic acid units by at least 5 ethylene glycol monomer units is found to be essential for high Fe(III) binding efficiency, while block copolymers are observed to be the best-suited architecture for polymer network and hydrogel formation via Fe(III) chelation.