A Raman Spectroscopic Study of the Initial Stages of Hydrolysis Oftetraethoxysilane

Barrie, James D.; Aitchison, Kenneth A.

doi:10.1557/proc-271-225

Cited by 7 publications

(4 citation statements)

References 15 publications

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“…Due to overlap-ping, no further bands attributable to silanols can be detected, except for hardly noticeable shoulders at the high wavenumber side of the 656 cm 2 1 band. This observation is consistent with the work of Barrie and Aitchinson, 28 who reported two bands at 675 and 701 cm 2 1 due to the n sym (SiO 4 ) m odes of triethoxysilanol and diethoxysilanediol, respectively. The comparatively high intensity of the band at 656 cm 2 1 suggests the monohydroxy species to be dominating in the sol at this stage.…”

Section: Resultssupporting

confidence: 93%

FT-Raman Spectroscopic Study of the Structural Evolution in Binary UV-Curable Vinyltriethoxysilane/Tetraethoxysilane Mixtures from the Sol to the Xerogel State

2002

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Fourier transform Raman spectroscopy was used in order to study acid catalyzed hydrolysis and polycondensation processes from the sol via the gel until the xerogel state in binary mixtures of vinyltriethoxysilane (ViTEOS) and tetraethoxysilane (TEOS). Supplementary 29Si-, 13C-MAS-NMR, and FT-IR data were considered. Intermediate hydrolysates, oligomers, and polycondensates were detected independently of the sample's physical state. Vibrational assignments are given for pure ViTEOS and its partially hydrolyzed intermediates. The corresponding mono-, di-, and tri-hydroxylated species are found to exhibit characteristic νsym(CSiO3) vibrational modes in the 650–672 cm−1 region. Subsequent oligomerization results in a progressive shift of the νsym(CSiO3) bands towards lower wavenumbers. Condensation proceeds faster in ViTEOS–TEOS mixtures than in pure ViTEOS. Assignments for some early oligomeric species and some network connectivity are given. The Raman spectra suggest that the main building blocks of the evolving network are already present in the wet gels. Moreover, it is shown that residual ethoxy groups attached to the siloxane network are still present in xerogels, whereas no silanol groups are detected. The spectra demonstrate that the vinyl groups did not react under the applied conditions. This system has potential for the preparation of UV-curable abrasion-resistant coatings for plastic substrates.

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Section: Resultssupporting

confidence: 93%

FT-Raman Spectroscopic Study of the Structural Evolution in Binary UV-Curable Vinyltriethoxysilane/Tetraethoxysilane Mixtures from the Sol to the Xerogel State

2002

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“…Bands for hydrolyzed monomers Si(OEt) 4− x (OH) x near 670 and 700 cm −1 have been reported , ; these strongly overlap with the TEOS band, resulting in the detection of only one broad band shifted to higher wavenumbers. Such a shift was not observed in Figure a, suggesting the absence of hydrolyzed monomers having sufficient lifetimes to be detected.…”

Section: Resultsmentioning

confidence: 99%

Time-Resolved in Situ Raman and Small-Angle X-ray Diffraction Experiments: From Silica-Precursor Hydrolysis to Development of Mesoscopic Order in SBA-3 Surfactant-Templated Silica

et al. 2007

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Time-resolved in situ Raman spectroscopy and small-angle X-ray diffraction have been combined in order to characterize the formation of hexagonal mesostructured SBA-3 silica. Experiments were performed under identical synthesis conditions in order to correlate the molecular and mesoscopic scales. Cetyltrimethylammonium bromide (CTAB) was used as the structuring agent with tetraethoxysilane (TEOS) as the silica precursor at a constant CTAB/TEOS molar ratio under highly acidic conditions and for various dilutions. Raman spectra allowed quantification of the release of ethanol that was produced solely by hydrolysis of TEOS under the experimental conditions used. The hydrolysis kinetics of TEOS was greatly enhanced in the presence of the surfactant as a result of micellar solubilization and surfactant stabilization of emulsion droplets. At the time of precipitation, the degree of TEOS hydrolysis depended strongly on the TEOS/CTAB concentration, decreasing with increasing concentration. The time evolution of the d-spacing and the full width at half-maximum of the (10) main reflection in the XRD pattern showed two distinct stages that were also strongly dependent on the sol composition. There seemed to be a coexistence of an ordered phase and a disordered one for a longer time in SBA-3 compared with MCM-41, clearly indicating that the ordering process is slower for SBA-3.

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“…In the majority of papers addressing the hydrolytic polycondensation of alkoxysilanes (e.g., refs −8), the authors neglect cyclization reactions. However, there is substantial evidence from vibrational , and nuclear magnetic resonance (NMR) 6,11-13 spectroscopy for three- and four-silicon cycles in siloxane polycondensation products (and there may well be larger cycles). There is also reason to believe that polycyclic structures (e.g., cages) exist.…”

mentioning

confidence: 99%

Importance of Cyclization during the Condensation of Hydrolyzed Alkoxysilanes

Rankin

Macosko²,

McCormick³

1998

Chem. Mater.

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A Raman Spectroscopic Study of the Initial Stages of Hydrolysis Oftetraethoxysilane

Cited by 7 publications

References 15 publications

FT-Raman Spectroscopic Study of the Structural Evolution in Binary UV-Curable Vinyltriethoxysilane/Tetraethoxysilane Mixtures from the Sol to the Xerogel State

FT-Raman Spectroscopic Study of the Structural Evolution in Binary UV-Curable Vinyltriethoxysilane/Tetraethoxysilane Mixtures from the Sol to the Xerogel State

Time-Resolved in Situ Raman and Small-Angle X-ray Diffraction Experiments: From Silica-Precursor Hydrolysis to Development of Mesoscopic Order in SBA-3 Surfactant-Templated Silica

Importance of Cyclization during the Condensation of Hydrolyzed Alkoxysilanes

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