engleski

Influence of the Polymerization Conditions on the Structure of Aminopropylsilanetriol

Aminopropylsilanetriol (APST) belongs to a new family of organosilane compounds with increasing industrial application. These molecules, deposited on different kinds of substrates like optical fibers, nanoparticals, semiconducting or metal materials, are forming chemical bonds with the surface of substrate changing thus their mechanical, optical or electrical properties. We investigated the solidification of aminopropylsilanetriol dissolved in water (~25%) under different conditions by Raman spectroscopy. The green line of an argon laser was used as the excitation source, and Raman spectra were recorded by triple monochromator in order to achieve good resolution and stray-light rejection. Some structure developments were also monitored by low- and mid-magnification microscope. The condensation was carried out at three different temperatures 80C, 230C and 600C. The influence of electromagnetic radiation in visible (514 nm) and UV (254 nm and 356nm) spectral range on the polymerization process was also investigated. Samples were deposited on three different substrates: plastic, glass and brass. Based on our DFT analysis of molecular vibrations of APST we could extract Raman bands characteristic for different molecular conformations (trans and gauche) as well as those corresponding to the formation of the Si-O-Si bonds in polymerized structures. The condensation process of APST at room temperature is very slow (several weeks). It can be accelerated by speeding up the evaporation by means of increasing the temperature or decreasing the humidity of the environment. The UV radiation also shortens the time needed for the polymerization, but at the same time it increases the fluorescence background and the noise in the Raman spectra. However, the analysis of some particular spectral intervals: low frequency (12-400 cm-1), Si-O-Si region and X-H region (X= C, N, O) indicates that the final structure is dependent on the sample history. The best ordered polymerized structure was found in the samples deposited on PVC substrate for which the condensation process was going on in dark for approximately three weeks. In those samples only the bands corresponding to trans conformer were detected, and the Si-O-Si stretching band at 1145 cm-1 had the highest intensity. This conclusion is supported by the fact that the Rayleigh line in these spectra is narrow enough that one can easily observe Bose peak at ~40 cm-1. The analysis of the Bose band indicates the existence of the medium range ordered structure.

aminopropylsilanetriol ; vibrations ; DFT potential ; temperature dependence ; dependence on substrate ; dependence on electromagnetic radiation

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