title: Iron tris(bipyridine) PEG hydrogels with covalent and metal coordinate cross-links.
abstract: Spontaneous gel formation of iron(II) tris(bipyridine)-centered poly(ethylene glycol) methacrylate ([Fe{bpy(PEG-MA)2}3]2+) was observed without the addition of a cross-linking agent. BpyPEG2 macroligands were first modified with methacrylate groups using methacrylic anhydride and then combined with FeSO4 to produce [Fe{bpy(PEG-MA)2}3]SO4. End group analysis by 1H NMR spectroscopy verified quantitative methacrylation of the PEG hydroxyl chain ends. A series of experiments and control reactions were performed to investigate the conditions required for gel formation. Hydrogels of [Fe{bpy(PEG-MA)2}3]SO4 were produced both in the presence and in the absence of a photoinitiator. Controls using MA-PEG-MA also formed hydrogels in the presence of [Fe(bpy)3]2+; however, the addition of a radical scavenger, TEMPO, prevented formation of a polymer network, suggesting radical involvement. Treatment of preformed hydrogels of bpy(PEG-MA)2 with aqueous solutions of FeSO4, CuBr2, and CoCl2 also produced materials with color changes indicative of complexation.
authors.affiliation: Department of Chemistry, University of Virginia, McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904-4319, USA.
authors.forename: Gina L
authors.initials: GL
authors.lastname: Fiore
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Klinkenberg
authors.forename: Anne
authors.initials: A
authors.lastname: Pfister
authors.forename: Cassandra L
authors.initials: CL
authors.lastname: Fraser
mesh_terms: D005296:Ferrous Compounds / Q000737:chemistry*; D020100:Hydrogels / Q000138:chemical synthesis / Q000737:chemistry*; D046911:Macromolecular Substances / Q000138:chemical synthesis / Q000737:chemistry; D008689:Methacrylates / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D013997:Time Factors
chemical_list: D005296:Ferrous Compounds; D020100:Hydrogels; D046911:Macromolecular Substances; D008689:Methacrylates; D011725:Pyridines; C515757:iron(II) tris(2,2'-bipyridine); C524499:polyethylene glycol methacrylate; D011092:Polyethylene Glycols