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Vibrational and 29 Si NMR spectroscopies of soluble silicate oligomers
Author(s) -
Bass Jonathan L.,
Turner Gary L.,
Morris Michael D.
Publication year - 1999
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19991400126
Subject(s) - depolymerization , silicate , trimer , raman spectroscopy , dilution , infrared spectroscopy , monomer , chemistry , ion , alkalinity , dimer , analytical chemistry (journal) , nmr spectra database , infrared , spectral line , inorganic chemistry , polymer , polymer chemistry , organic chemistry , physics , astronomy , optics , thermodynamics
Vibrational spectroscopy has been used to correlate the features of silicate solution spectra with 29 Si NMR spectra, as a function of SiO 2 :Na 2 O ratio and SiO 2 concentration. Assignments of infrared and Raman component bands have been made for different anion types and are consistent with results reported for crystalline silicates and silicate glasses. The extent of depolymerization of larger anions has been found to differ, depending on both the degree of dilution and alkalinity. The relative amounts of polymeric (Q 4 ) silica and larger three dimensional (Q 3 4R ) anions are greater for the more siliceous solutions (3.3 and 2.95 ratio) at high concentrations. These large anions continue to be major contributors to the anion distribution even at 15 to 50 fold dilution. In the case of more alkaline solutions, especially below 2.5 ratio, the relative contribution of the large anions to the distribution drops rapidly, even with 2 or 3 fold dilution. At low concentrations, in very alkaline solutions, the anion distribution is mainly monomer, dimer and cyclic trimer. Vibrational spectroscopies show great promise for observing changes in anion distribution on a much shorter time scale than is possible with 29 Si NMR and can be useful for following reactions involving silicate solutions.