Abstract
The influence of low ligand/Zr mole ratios (ρ = 0–0.1) on the hydrolysis and growth of oligomers from Zr(OnPr)4 modified with a series of β-diketones (trifluoroacetylacetone, hexafluoroacetylacetone, benzoylacetone, dibenzoylmethane and dipivaloylmethane), and their subsequent aggregation to form uniform, dense spheres, has been investigated by light scattering and turbidometry. The addition of β-diketones results in a large increase in the induction time, t i (reduction in hydrolysis/condensation rates). A remarkable feature of the data is the dramatic reductions in rate observed even when a maximum of one in forty Zr–OR bonds have been replaced by the β-diketone and are no longer available for hydrolysis or further condensation. The largest effect is observed with dibenzoylmethane, which increases t i by a factor of 26 relative to acetylacetone.
A mechanism rationalising the origin of the effect is discussed, which involves segregation of the β-diketone ligands on the surface of the growing particle, with subsequent particle growth restricted to those sites not occupied by the chelating ligands.
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M. J. Percy, J. R. Bartlett, J. L. Woolfrey, L. Spiccia, and B. O. West, manuscript in preparation.
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Percy, M., Bartlett, J., Spiccia, L. et al. The Influence of β-Diketones on the Hydrolysis and Growth of Particles from Zirconium(IV) n-Propoxide. Journal of Sol-Gel Science and Technology 19, 315–319 (2000). https://doi.org/10.1023/A:1008781515324
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DOI: https://doi.org/10.1023/A:1008781515324