A general concept for the introduction of hydroxamic acids into polymers. Issue 29 (17th June 2019)

• Record Type: Journal Article
• Authors: Johann, Tobias; Keth, Jennifer; Bros, Matthias; Frey, Holger
• Is Part Of: Chemical science. Volume 10:Issue 29(2019)
• Page Start: 7009
• Page End: 7022
• Publication Date: 2019-06-17
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c9sc02557j
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : Polyethers (PEG) with hydroxamic acid groups enable chelation of a variety of metal ions, coating of metal oxide surfaces and stabilization of nanoparticles. In contrast to catechol, hydroxamic acids are oxidation stable and biocompatible. Abstract : Hydroxamic acids (HA) form stable complexes with a large variety of metal-ions, affording hydroxamates with high complexation constants. Hydroxamic acid moieties play a crucial role in the natural iron metabolism. In this work, 1, 4, 2-dioxazoles linked to a hydroxyl group are introduced as key compounds for the installation of hydroxamic acids at synthetic polymers in well-defined positions. A general synthetic scheme is developed that gives access to a series of novel functional key building blocks that can be universally used to obtain hydroxamic acid-based monomers and polymers, for instance as protected HA-functional initiators or for the synthesis of a variety of novel HA-based monomers, such as epoxides or methacrylates. To demonstrate the excellent stability of the dioxazole-protected hydroxamic acids, direct incorporation of the dioxazole-protected hydroxamic acids into polyethers is demonstrated via oxyanionic polymerization. Convenient subsequent deprotection is feasible under mild acidic conditions. α-Functional HA-polyethers, i.e. poly ethylene glycol, polypropylene glycol and polyglycerol based on ethylene oxide, propylene oxide and ethoxy ethyl glycidyl ether, respectively are prepared with low dispersities (<1.2) in the molecular weight range of 1000 to 8500 g mol −1 . Water-soluble hydroxamic acid functional poly(ethylene glycol) (HA-PEG) is explored for a variety of biomedical applications and surface coating. Complexation of Fe(iii ) ions, coating of various metal surfaces, enabling e.g., solubilization of FeO x nanoparticles by HA-PEGs, are presented. No impact of the polyether chain on the chelation properties was observed, while significantly lower anti-proliferative effects were observed than for deferoxamine. HA-PEGs show the same complexation behavior as their low molecular weight counterparts. Hydroxamic acid functional polymers are proposed as an oxidatively stable alternative to the highly established catechol-based systems.