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(a) Calculated pKa of neutral and protonated amino silane in water by the Jaguar software 16 , and (b) the intramolecular catalysis and reaction between the protonated methanol and amino (NH 2 ) groups in ATES.
Source publication
Alkoxysilanes and organoalkoxysilanes are primary materials in several industries, e.g. coating, anti-corrosion treatment, fabrication of stationary phase for chromatography, and coupling agents. The hydrolytic polycondensation reactions and final product can be controlled by adjusting the hydrolysis reaction, which was investigated under a variety...
Context in source publication
Context 1
... inhibition effect of acetic acid can be explained by the protonation of the amino group, where its pK a and β values are respectively 10 and 0.735, which leads to the consumption of a proton in the protonation of the amino group instead of the ethoxy group. Figure 4 shows the intramolecular catalysis in amino silanes, the inhibition effect of the acid, and the formation of non-methoxy monomers. ...
Citations
... The sol-gel process is very sensitive to the chemical environment, and hence an important consideration when designing OIHs is to understand the potential impact of the organo-functionalized groups on the sol-gel process. Issa et al. [31] investigated organoalkoxysilane hydrolysis through a combined experimental/theoretical approach, employing gas chromatography and computational calculations to determine the hydrolysis rates of various organoalkoxysilanes, such as entries 3, 4, 5 and 6 ( Fig. 1). This investigation was conducted under different sol-gel processing conditions, including acid, alkaline, and sodium fluoride catalysis, and with protic, polar aprotic, and nonpolar aprotic solvents. ...
... As mentioned in an interesting review [20] by the same author, organic groups with amino, carbonyl or ester groups can exhibit such intramolecular catalysis. Also, the organic group can interact with the solvent by hydrogen bonding, enhancing the hydrolysis rate [20,31]. The stabilization of the transition state is fundamental to the formation of silanol groups, but steric effects must also be considered. ...
The integration of organic components into inorganic silica systems through sol–gel synthesis has significantly expanded the potential applications of these materials by enhancing features such as transparency, crack resistance, flexibility, and the introduction of new functional groups. Understanding the influence of organic groups on the sol–gel process and exploring various approaches to crafting organic-inorganic hybrid (OIH) silica systems are essential endeavors. This review aims to provide a comprehensive guide, particularly targeted towards researchers new to OIH synthesis. It delineates the key parameters of the sol–gel process, presents five distinct synthesis strategies, and provides exemplary applications. Beyond traditional methods like co-condensation with organoalkoxysilanes and bridged-organoalkoxysilanes, alternative strategies are elucidated, including biopolymer functionalization, photopolymerization enabling 3D printing, and utilization of polyhedral oligomeric silsesquioxanes (POSS). Furthermore, recent literature exploration has uncovered promising optical applications for OIH materials. These materials serve as excellent hosts for luminophores due to their inherent transparency and the synergistic interactions between the organic functional groups and luminophores, which can enhance properties such as quantum yield, particularly with lanthanides, and even improve the photochromic performance of polyoxometalates. Consequently, OIH materials find extensive utilization in optical technologies, encompassing luminescent solar concentrators, light-emitting diodes, photochromism, random lasers, optical sensing, and various optical components, as we aim to demonstrate comprehensively herein.
Graphical Abstract
... Silica nanoparticles with mesopores in the range of 2-30 nm are commonly prepared via the condensation of silica precursors (silica alkoxides TEOS, TMOS [7][8][9], their functionalized derivatives [10], sodium silicates [11]) in the presence of surfactant micelles and a catalyst in an aqueous medium [12]. This process is affected by the surfactant concentration [13,14], the type and amount of the hydrolyzing agents [7,8,[15][16][17][18][19][20][21][22][23], the presence of various kosmotropic and chaotropic salts [12,[24][25][26][27][28][29][30][31][32][33][34][35], alcohol additives [8,9,[36][37][38][39] and the degree of dilution [8,17,22,40]. ...
Silica nanoparticles synthesized solely from organosilanes naturally possess a greater number of organic functionalities than silica nanoparticles surface-modified with organosilanes. We report the synthesis of organically modified silica (ORMOSIL) nanoparticles with a mesoporous and surface-rough morphology and with a high surface area, made solely from vinyltrimethoxy silane. We chemically modified these vinyl silica nanoparticles using bromination and hydroboration, and demonstrated the high accessibility and reactivity of the vinyl groups with an ~85% conversion of the functional groups for the bromination of both particle types, a ~60% conversion of the functional groups for the hydroboration of surface-rough particles and a 90% conversion of the functional groups for the hydroboration of mesoporous particles. We determined that the mesoporous vinyl silica nanoparticles, while having a surface area that lies between the non-porous and surface-rough vinyl silica nanoparticles, provide the greatest accessibility to the vinyl groups for boronation and allow for the incorporating of up to 3.1 × 106 B atoms per particle, making the resulting materials attractive for boron neutron capture therapy.
... the type and amount of hydrolyzing agents [7,8,[15][16][17][18][19][20][21][22][23] the presence of various kosmotropic and chaotropic salts [12,[24][25][26][27][28][29][30][31][32][33][34][35]. alcohol additives [8,9,[36][37][38][39] and the degree of dilution [Error! Bookmark not defined.,Error! ...
Silica nanoparticles synthesized solely from organosilanes naturally possess a greater number of organic functionalities than silica nanoparticles surface modified with organosilanes. We report the synthesis of organically modified silica (ORMOSIL) nanoparticles with mesoporous and surface rough morphology and with high surface area, made solely from vinyltrimethoxy silane. We chemically modified these vinyl silica nanoparticles using bromination and hydroboration, and demonstrated the high accessibility and reactivity of the vinyl groups with an ~85% conversion of the functional groups for bromination of both particle types, a ~60% conversion of the functional groups for hydroboration of surface rough particles and a 90% conversion of the functional groups for hydroboration of mesoporous particles. We determined that the mesoporous vinyl silica nanopar-ticles, while having a surface area that lies between the non-porous and surface rough vinyl silica nanoparticles, provide the greatest accessibility to the vinyl groups for boronation and allow in-corporating up to 3.1 × 106 B atoms per particle, making the resulting materials attractive for boron neutron capture therapy.
... [34,35] One of the best known and most widely used organotriethoxysilanes is 3-aminopropyl(triethoxysilane) (APTES), which has an amino group in its structure that promotes the hydrolysis and condensation of alkoxy groups, as well as attachment to a surface. [36,37] We suggested that, by analogy with the self-catalytic ability of APTES, 1,4-disubstituted 1,2,3-triazols in the structure of organotrialkoxysilanes can promote the hydrolysis and condensation of the alkoxy group due to the interaction of 3- (1-1) nitrogen of the 1,4-disubstituted triazole with water and the formation of a hydroxyl anion that triggers hydrolysis (Figure 5). [38] To test the hypothesis, we conducted a model experiment, where silane was used as a triazole-containing organoalkoxysilane 3-4 ( Figure 6). ...
Organotrialkoxysilanes are unique compounds that play an important role in modern science and industry. Their structure determines their varied use both in production and academic research. The development of the synthesis of organotrialkoxysilanes and polymers based on them, taking into account environmental realities, is an important task. In our work, we present an original approach for the preparation of organotriethoxysilanes, starting from azidoalkyltriethoxysilanes and various types of substrates containing a terminal triple bond, by the azide‐alkyne cycloaddition (CuAAC) mechanism without the use of solvents, catalyst ligands, and amines. We also found the self‐catalyzing effect of the triazole fragment resulting from the azide‐alkyne cycloaddition in the reaction of hydrolysis and condensation of alkoxy groups, which made it possible to obtain a series of silsesquioxane products only by adding water, without the use of catalysts. As a result, a new, original scheme for the preparation of organosilicon organotrialkoxysilanes of a monomeric structure with their subsequent transformation into silsesquioxane polymers under “green” conditions is built.
... The intercalation of silane long-chained functional groups will not only increase the distance between GO sheets, but they will also impair the cross-linking between the functional groups of GO, thus reducing agglomeration and assisting in the dispersion. In addition, the stronger positively charged amino groups in the surface functional groups of GO-APTS provided greater repulsive forces that reduced their chances of contacting each other which caused subsequent agglomeration [48]. Fig. 4 showed the heat flow and total heat released by the control, 0.05 wt% GO and 0.05 wt% GO-APTS samples. ...
Graphene oxide (GO) and 3-aminopropyltriethoxy silane (APTS) have been successfully used in geopolymers to solve specific problems. Nevertheless, the dispersion of GO to strengthen the matrix remains a challenge owing to the characteristic high alkalinity of geopolymer binders. Concurrently, independent addition of APTS to improve the workability severely retards geopolymer dissolution and condensation reactions. In this paper, an attempt is made to mutually exploit benefits of these two additives through a surface functionalisation approach whereby surface functional groups of GO were modified by APTS to provide repulsive effects that could better isolate the GO nanosheets from each other, while the accelerating effects of GO on the geopolymerisation process compensated for the retardation effects of APTS. The structure of GO-APTS was observed to be stable in the highly alkaline sodium silicate environment and significantly improved the dispersion of the nanosheets in the geopolymer composite according to the UV–Vis and SEM/TEM observations. Furthermore, the nucleation and reinforcing effects of GO were enabled by APTS. The GO-APTS–cement samples not only demonstrated better workability and transport properties compared with the reference and pure GO samples, but also superior mechanical strength, with improvements in tensile strength of ∼110% and ∼52% at 7 and 28 days, respectively. These findings evidence the effectiveness and potential of silane-functionalised GO in overcoming the dispersion issues experienced by GO in the highly alkaline media of geopolymers while simultaneously enhancing the mechanical and durability performance of geopolymer systems.
... Issa et al. [34] investigated the hydrolysis mechanism of 3-cyanopropyltriethoxysilane (CTES). They found that the activation energy (∆G ǂ ) of CTES hydrolysis in methanol and ethyl acetate resulted from an intermediate step, i.e., re-esterification in the case of methanol and hydrolysis of ethyl acetate at high temperatures, to produce acetic acid and ethanol and autocatalysis by acetic acid. ...
Mild steel continues to be the most extensively used construction material in several industries and constructions. However, corrosion of mild steel in aggressive environments is a major concern. Under the tremendously increasing demand for improving the coatings strategies because of the environmental concerns due to some of the traditional coatings, silane pre-treatments have been emerging as one of the effective solutions, among other strategies. Different approaches, such as adding particles of metal oxide (such as SiO2, ZrO2, Al2O3, TiO2 and CeO2), incorporating plant extracts and impregnating 2D materials into the coatings, have been employed for durable corrosion resistance, including for mitigating enhanced corrosion due to the presence of bacteria. This review discusses the critical mechanistic features of silane coatings such as the role of hydrolysis and condensation in the bonding of silanes with metal surfaces. The factors that influence the performance of the silane coatings for corrosion resistance of mild steel are discussed. In particular, this review provides insight into silane coatings for mitigating microbiologically influenced corrosion (MIC) of mild steel.
... A hydrogen bond can then form between the oxygen in the ethoxy groups of VTES and a hydrogen atom that links to a N atom of a protein. This bond might encourage the hydrolysis of VTES with a water molecule (attracted to proteins) to form silanol groups [21]. ...
This work presents insights into how naturally occurring proteins affect the graft copolymerization of vinyltriethoxysilane (VTES) on natural rubber (NR) latex. Four NR latexes with different protein contents were subjected to graft copolymerization catalyzed by tert-butyl hydroperoxide (TBHP)/tetraethylene pentamine (TEPA) initiators. The four NR latexes were freshly tapped natural rubber (fresh NR), high-ammonia natural rubber, deproteinized natural rubber (DPNR), and protein-free natural rubber (PFNR). During the graft copolymerization on the studied latexes, VTES conversion depended on the protein content of the NR latexes. The formation and morphology of silica were investigated by Fourier transform infrared spectroscopy, solid-state NMR spectroscopy, and transmission electron microscopy. Among the products, fresh NR-graft-poly(VTES) exhibited the highest tensile strength and highest protein content. Proteins were confirmed to function as catalysts for the hydrolysis and condensation of VTES when graft copolymerization was performed on fresh NR (ammonia-free), fresh NR containing ammonia, and DPNR without TBHP/TEPA initiators. Our work studied the effect of proteins on the graft copolymerization of vinyltriethoxysilane (VTES) on natural rubber (NR) latex. Stress at break of the graft copolymers was substantially higher when proteins were present; that is, the stress at break of fresh NR-graft-PVTES was higher than that of protein-free NR-graft-PVTES. Silica nanomatrix was formed more visibly in the presence of proteins, as observed by transmission electron microscopy. Furthermore, proteins were found to accelerate the formation of silica particles by forming hydrogen bonds with VTES molecules and enhancing hydrolysis with water molecules.
... A brief overview of the core literature on the preparation of MSN colloids can be found in the Supporting Information. It covers the role of the surfactant concentration [25][26][27][28], the type and amount of hydrolyzing agents [11,12,22,[29][30][31][32][33][34][35][36], the effect of various kosmotropic and chaotropic salts [10,24,[37][38][39][40][41][42][43][44][45][46][47][48][49], alcohol additives [12,13,[50][51][52][53], and the degree of dilution [12,30,35,54] in the nanoparticle formation mechanism. However, despite a large number of publications on the MSN synthesis and applications, the vast data on MSN preparation, undeniably valuable from the experimental point of view, is still poorly understood. ...
Near monodisperse mesoporous silica nanoparticles (MSN) represent a promising and rapidly developing type of mesoporous silica materials; however, the vast data on their synthesis remains unorganized and ill-understood. We systematically studied the formation of MSN under basic and neutral conditions using various temperatures, CTAB concentrations, hydrolyzing agents (triethanolamine, ammonia, phosphate buffers), and media with different colloidal stabilization properties (with ethanol as a cosolvent and monovalent salts). In the typical conditions for the preparation of stable MSN colloids, the particle size was controlled by colloidal stabilization by the medium (solvent type, ionic strength, and surfactant concentration) in agreement with the “aggregative growth” mechanism, rather than by solely the hydrolysis and condensation rates conventionally used for data interpretation in the classical nucleation theory. Medium properties (pH, ion types and concentration, polarity) also defined the efficiency of silica-surfactant cooperative self-assembly, which directly affected the porosity, mesopore size and pore wall thickness. Interestingly, this traditional silica-surfactant route showed a limited effect on the particle size, emphasizing the dominating role of colloidal stabilization in the studied reaction conditions. In situ pH measurements showed that every reaction medium has unique pH evolution profiles depending on the buffer capacity, hydrolysis and condensation rates. Reaction systems that fail to maintain the working pH can lead to non-porous products or undesired particle morphology and size distribution. The established particle formation mechanism allowed us to formulate comprehensive guidelines for preparing relatively concentrated colloids of near monodisperse (PDI 5-15%) mesoporous 30-700 nm silica spheres with variable porosity and mesopore size. These findings will be particularly useful in designing new mesoporous silica-containing materials for biomedical applications.
... This is due to the relative rates of the hydrolysis and condensation reactions. In general, the hydrolysis step gets progressively slower under acidic conditions and faster under basic conditions [19]. ...
Sol-Gel is a low cost, well-established and flexible synthetic route to produce a wide range of micro- and nanostructures. Small variations in pH, temperature, precursors, time, pressure, atmosphere, among others, can lead to a wide family of compounds that share the same molecular structures. In this work, we present a general review of the synthesis of LaMnO3, SrTiO3, BaTiO3 perovskites and zinc vanadium oxides nanostructures based on Sol-Gel method. We discuss how small changes in the parameters of the synthesis can modify the morphology, shape, size, homogeneity, aggregation, among others, of the products. We also discuss the different precursors, solvents, working temperature, reaction times used throughout the synthesis. In the last section, we present novel uses of Sol-Gel with organic materials with emphasis on carbon-based compounds. All with a perspective to improve the method for future applications in different technological fields.
... After this, a pair of free silanol groups can condense with each other, either directly or via alkoxy groups. 29 The addition of different TMOS:phTEOS ratios promotes various ways of three-dimensional silica formation. The condensation of TMOS occurs in all four directions of alkoxy groups, resulting in a relatively dense network, which subsequently envelops the NCs (Scheme S1A). ...
