Butyl-Methyl-Pyridinium Tetrafluoroborate Confined in Mesoporous Silica Xerogels: Thermal Behaviour and Matrix-Template Interaction

Abstract

Organic-inorganic silica composites have been prepared via acid catalyzed sol-gel route using tetramethoxysilan (TMOS) and methyl-trimethoxysilane (MTMS) as silica precursors and n-butyl-3-methylpyridinium tetrafluoroborate ([bmPy][BF4]) as co-solvent and pore template, by varying the content of the ionic liquid (IL). Morphology of the xerogels prepared using the ionic liquid templating agent were investigated using scanning electron microscopy and small angle neutron scattering (SANS). Thermal analysis has been used in order to evaluate the thermal and structural stability of the materials, in both nitrogen and synthetic air atmosphere. In nitrogen atmosphere, the IL decomposition took place in one step starting above 150 °C and completed in the 150–460 °C temperature interval. In synthetic air atmosphere, the IL decomposition produced two-step mass loss, mainly in the 170–430 °C temperature interval. The decomposition mechanism of the IL inside the silica matrix was studied by mass spectrometric evolved gas analysis (MSEGA). The measurements showed that the degradation of the IL’s longer side chain (butyl) starts at low temperature (above 150 °C) through a C-N bond cleavage, initiated by the nucleophilic attack of a fluorine ion.

On-Line Thermally Induced Evolved Gas Analysis: An Update—Part 1: EGA-MS

“…Thermal analysis has been used in order to evaluate both the thermal and structural stability of the materials (nitrogen and synthetic air atmosphere) and the decomposition mechanism inside the silica matrix (mass spectrometric evolved gas analysis). The measurements showed that the degradation of the longer side chain (butyl) starts at low temperature (above 150 °C) through a C-N bond cleavage, initiated by the nucleophilic attack of a fluorine ion [ 170 ].…”

Imidazolium Ionic Liquids as Designer Solvents Confined in Silica Nanopores

“…On the other hand, short-chain ILs do not form proper micelles [ 14 ], but do agglomerate or self-associate, providing confinement and promoting the agglomeration of the condensed silica species [ 9 ]. In our previous study, new composite materials using a short alkyl chain ionic liquid, N-butyl-3-methylpyridinium tetrafluoroborate as templating agent, and tetramethoxysilane (TMOS) and methyl-trimethoxysilane (MTMS) as silica precursors have been prepared [ 23 ]. Varying the amount of the IL over a broad range, the slowing of the condensation reaction and increase in the silica particle size could be observed [ 23 ].…”