Interactions between metal ions and ligands in metal-containing polymers involve two bonding extremes: persistent covalent bonding, in which the polymers are essentially static in nature, or labile coordination bonding, which leads to dynamic supramolecular materials. Main-chain polymetallocenes based on ferrocene and cobaltocene fall into the former category because of the presence of strong metal–cyclopentadienyl bonds. Herein, we describe a main-chain polynickelocene—formed by ring-opening polymerization of a moderately strained nickelocenophane monomer—that can be switched between static and dynamic states because of the relatively weak nickel–cyclopentadienyl ligand interactions. This is illustrated by the observation that, at a low concentration or at an elevated temperature in a coordinating or polar solvent, depolymerization of the polynickelocene occurs. A study of this dynamic polymer–monomer equilibrium by 1H NMR spectroscopy allowed the determination of the associated thermodynamic parameters. Microrheology data, however, indicated that under similar conditions the polynickelocene is considered to be static on the shorter rheological timescale.
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Self-assembly of metal–organic polyhedra into supramolecular polymers with intrinsic microporosity
Nature Communications Open Access 12 July 2018
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R.A.M., A.D.R., G.R.W. and I.M. thank the Engineering and Physical Sciences Research Council (EPSRC) for funding. D.W.H. is supported by a EPSRC doctoral training centre grant [EP/G036780/1]. The authors thank B. MacCreath for assistance in performing the DLS microrheology measurements.
The authors declare no competing financial interests.
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Musgrave, R., Russell, A., Hayward, D. et al. Main-chain metallopolymers at the static–dynamic boundary based on nickelocene. Nature Chem 9, 743–750 (2017). https://doi.org/10.1038/nchem.2743
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