Structural and thermal characterization of hybrid materials based on TEOS and DCN

Abstract

Solution and solid-state Silicon-29 NMR spectroscopy, X-ray diffraction (WAXS), infrared spectroscopy (IR), thermogravimetric analysis (TGA), and differential scanning calorimetric were used for the characterization of organic-inorganic hybrids, obtained from 4- [[5-dichloromethylsilyl]pentyl]oxy]-cyanobenzene (DCN) and tetraethoxysilane (TEOS). Presence of reaction intermediates during chemical reactions was characterized by NMR. The hybrids are mainly composed of a siloxane copolymer with silicate units. Copolymer has pendant groups of pentyl-oxycyanobenzene that behave as chromophores. The nature of ordered-disordered phases was analyzed by X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. Ordered phase has a mesogenic structure containing the siloxane copolymer. The disordered phase is mainly silica glass. Molecular modeling for an idealized section of the copolymer suggests that pentyl-oxy-cyanobenzene side-chains align as rigid mesogens along the polymer backbone. Hybrids present self diffraction patterns in coherent luminous rings forms. These patterns indicate the presence of nonlinear optic (NLO) properties.

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“…11(c)]. However, the formation of regions with intermolecular packing order has been detected by means of wide‐angle X‐ray diffractometry 17. In comparison with the spectrum of DCN–TEOS in solution, an upfield shift for the methyl A and methylene B carbons can be observed.…”

“…5‐Bromo‐1‐pentene and 4‐cyanophenol were used to obtain 4‐[(pentenyl)oxy]cyanobenzene, as described elsewhere 17, 18. After purification, the olefin was reacted with dichloromethylsilane in the presence of hexachloroplatinic acid, under a nitrogen atmosphere, to obtain DCN‐Cl 2 .…”

“…We have recently reported the synthesis of hybrids based on a diorganodichlorosilane, 4‐[(5‐dichloromethylsilyl)pentyloxy]cyanobenzene (DCN‐Cl 2 )] and TEOS 17. The nature of the starting solution is complex because it includes three solvents [water, tetrahydrofuran (THF), and toluene], two solutes (DCN‐Cl 2 and TEOS), and a strong acid (HNO 3 ).…”

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“…32 Further, the presence of peak at d ¼ 66.2 ppm (-CH 2 -O-Si-) conrmed the inclusion of IPTES in polymer matrix. 33 3.6. Morphological studies (i) Transmission electron microscopy (TEM) analysis.…”