Controlled stabilisation of silicic acid below pH 9 using poly(1-vinylimidazole)
We show, for the first time, inhibition of silicic acid condensation over a wide range of pH, especially below 9 using certain molecular mass fractions of poly(1-vinylimidazole) (PVI). This is achieved by stabilisation of molybdate-active Si species, which are crucial to condensation and growth to form silica. The structure of the resulting composites depends on the molecular mass of the PVI chains. Long-chain macromolecules can "encapsulate" Si species giving rise to stable soluble complexes. Short PVI chains stimulate association of silica particles and at neutral pH precipitation occurs. Protonation of imidazole units in acidic pH results in dissolution of the precipitates. We believe that the results presented herein using PVI as a model system will help elucidate the mechanisms underpinning the molecular interactions between (bio)macromolecules and inorganic materials.
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