followed the sol-gel process of methyltrimethoxysilane by measuring the peak intensity variation of silanol (Si-OH) groups generated from hydrolysis and siloxane bridges (Si-O-Si) from condensation and in so doing, introduced the silica particle growth mechanism 15. investigated the activation energy and Arrhenius factor of the hydrolysis of methyltriethoxysilane under different temperatures 14. monitored the hydrolysis and condensation reactions of tetraethyl orthosilicate (TEOS) under rich water conditions and suggested that the hydrolysis is a first-order reaction 13. In a few examples, Tejedor-Tejedor et al. However, FTIR analysis of aqueous silica sol-gel is seldom reported. The use of Fourier transform infrared spectroscopy (FTIR) is widely used for examining the evolution of the silica frameworks through their functional groups in a sol-gel reaction system 6, 7, 8, 9 and xerogel characterisation 10, 11, 12. To effectively tailor the porosity of xerogels by the sol-gel method, it is necessary to understand how the reactions influence the porous structure formation, arising from the formation of silanol (Si-OH) groups via hydrolysis and siloxane (Si-O-Si) bridges via the condensation reaction. Here, the reactant ratios, pH of the solution, reaction temperature and nature of silica precursor all affect the reaction mechanisms and kinetics 4, 5 and the final xerogel structure. The silica sol-gel method generally comprises of reacting a silica precursor in the presence of solvents and catalysts by the well-established hydrolysis and condensation reactions. Silica porous materials have attracted growing scientific interest due to their unique properties in terms of large surface area, thermal stability and chemical inertness and consequently have found diverse applications in absorption 1, catalysis 2, energy 2 and separation applications 3. This tailoring process facilitated further condensation reactions and crosslinking of silica chains, which coupled with stiffening of the network, made it more resistant to compression and densification. Contrary to dense silica structures obtained from sol-gel reactions in the miscible region, higher microporosity was produced via a phase-separated sol-gel system by using high H 2O/Si ratios. This was attributed to the concentration of the reactive sites around the phase-separated interface, which enhanced the condensation and crosslinking. A mesoporous structure was obtained at low temperature due to weak drying forces from slow solvent evaporation on one hand and formation of unreacted ES40 cages in the other, which reduced network shrinkage and produced larger pores. The solution composition within the immiscible region of the ES40 phase-separated system shows that the hydrolysis and condensation reactions decreased with decreasing reaction temperature. This oligomeric silica precursor underwent various degrees of phase separation behaviour in solution during the sol-gel reactions as a function of temperature and H 2O/Si ratios. A ternary phase-separation investigation of the ethyl silicate 40 (ES40) sol-gel process was conducted using ethanol and water as the solvent and hydrolysing agent, respectively.
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