engleski

Vibrational analysis of 3-Glicidoxypropyltrimethoxysilane polymer

3-Glicidoxypropyltrimethoxysilane (GPTMS) molecule possesses two functional groups, epoxy and silicon alkoxide, enabling it to form both organic and inorganic polymers, respectively. Main interest of this work is the characterization of the inorganic GPTMS polymer structure obtained by hydrolysis of the methoxy groups which gives silanol groups (SiOH). Condensation of silanols forms siloxane (SiOSi) bonds. In this work GPTMS polymer with inorganic SiOSi bonds was prepared by a sol-gel process. The structure of polymer was characterized by vibrational spectroscopy (Raman and IR). The interpretation of vibrational spectra is supported by the normal coordinate analysis based on density functional theory (DFT) calculations of expected polymer structures. DFT calculations have been carried out by 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. The comparison of theoretical spectra with the experimental data enabled us to extract the characteristic vibrational bands of polymer structures. GPTMS molecule has characteristic fundamentals at 1256 cm-1 (mode of epoxy ring) as well as SiO stretching modes at 642 and at 612 cm-1. The SiO stretching vibrations are not evident in spectra of GPTMS polymer indicating the condensation of methoxy groups and possibility of inorganic SiOSi polymerization. The intense Raman band observed at 1136 cm-1 and assigned to the SiOSi stretching vibrations suggests the ladder-type structure of GPTMS polymer.

3-Glicidoxypropyltrimethoxysilane; Raman Spectroscopy; IR; Density-functional calc.; Force-field calc.

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