engleski

Density functional study of gamma-aminopropyltriethoxysilane

Aminofunctional organosilanes, such as gamma-aminopropyltriethoxysilane (APTES) provide superior bonds between inorganic substrates and organic polymers. The Raman and IR spectroscopy have been recognized as powerful tools for investigation of surface modification by silanization, the reaction applied in numerous fields of nanotechnology. Therefore, we have performed the investigation of structure and vibrational spectra of APTES. FT Raman and IR spectra of liquid APTES were recorded in frequency region from 100 cm-1 to 3500 cm-1 and from 500 cm-1 to 4000 cm-1, respectively. The density functional theory calculations using Becke’ s three-parameter exchange functional in combination with the Lee-Young-Parr correlation functional (B3-LYP) and standard 6-311+G(d, p) basis set were carried out to study the conformational stability and vibrational spectra of APTES. Calculations reveal the existence of two stable conformers trans and gauche. The structural parameters obtained from the optimized geometry for trans conformer were used to obtain the potential energy surface for conformational interchange. The torsion (dihedral) CCCSi angle allowed to vary in 1.8 steps between -180 and 180 while the other structural parameters were held fixed at the optimized values for the trans conformer The calculated energie for the gauche conformation was found to be 608 cm-1 above the minimum energy of the trans conformation. An assignment of the fundamental vibrational frequencues based on the normal coordinate analysis, characteristic group frequencies, caclulated IR intensities as well as Raman activities is proposed for both conformers. DFT/B3LYP Cartesian force-constants matrix was transformed into local symmetry coordinates and scaled to reproduce the experimental frequencies. The scaling factors are transfered from aminopropylsilanetriol. Temperature dependence of Raman spectra of liquid AMPTES and DFT calculation enabled us to identifie the vibrational bands characteristic for both conformers.

gamma-aminopropyltriethoxysilane; DFT

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