Addition Of Tetraethoxysilane Research Articles

Protective Coatings Based on the Organosilicon Derivatives of Fatty Acids Obtained by the Thiol-Ene Click Reaction.

This article describes the synthesis of a hydrophobic protective coating for concrete based on a silane derivative of fatty acids. The coating was obtained through a thiol-ene click addition reaction using methyl oleate and 3-mercaptopropyltrimethoxysilane in the presence of the photoinitiator 2,2-dimethoxy-2-phenylacetophenone (DMPA). This reaction proved to be more efficient compared with other tested (photo)initiators, considering the double bond conversion of oleate. The coating was applied to concrete using two methods: immersion and brushing. Both methods exhibited similar consumption of methyl oleate-based silane (UVMeS) at approximately 20 g/m2. The hydrophobic properties of the coatings were evaluated based on the contact angle, which for the modified surfaces was above 93°, indicating their hydrophobic nature. The penetration depth of the silane solution into the concrete was also studied; it was 5-7 mm for the immersion method and 3-5 mm for the brushing method. The addition of tetraethoxysilane (TEOS) to the silane solution slightly improved the barrier properties of the coating.

Effect of tetraethoxysilane on the dimensional stability and static bending properties of nanocellulose, tannin, and activated carbon mixed with epoxy resin

Static bending strength and dimensional stability of epoxy composite is an important property for most of the structural applications. Types of filler used with addition of tetraethoxysilane (TEOS) in the epoxy system might improve the properties of the composite. In this research paper, two types of epoxy composites were prepared: the first batch involved epoxy resin mixed with three different fillers; nanocellulose, tannin, and activated carbon at three different doses; 5%, 10% and 15%, while the second batch was a reactive modification using 1%, 2% and 3% doses of (TEOS) as cross-linker agents at 10% dose of each filler. The dimensional stability and static bending properties of epoxy mixed with commercial nanocellulose, tannin, and laboratory-made activated carbon as fillers were investigated. We found that the nanocellulose, tannin, and activated carbon acted as hydrophobic buffer to slow the water absorption at the 10% dose. The thickness swelling was also significantly lower (P < 0.05) for the epoxy mixed with any fillers regardless of the dose. The modulus of rupture (MOR) was also significantly higher (P < 0.05) in epoxy mixed with the 10% dose of nanocellulose and tannin. Overall, the water absorption and thickness swelling were lowest in epoxy mixed with the 10% dose of nanocellulose. The use of the 3% dose of TEOS in epoxy mixed with a 10% dose of tannin gave the highest static bending. The TEOS was only suitable for epoxy mixed with tannin.

Development of a reusable fluorescent nanosensor based on rhodamine B immobilized in Stöber silica for copper ion detection.

This work has the goal of developing and evaluating a reusable fluorescent nanosensor for detection of Cu(ii) ion in aqueous solution, based on the immobilization of rhodamine B in silica nanoparticles prepared according to a modified Stöber method. In order to do this, a standard ammonium hydroxide ethanolic solution was mixed to ethanol under constant stirring, followed by the addition of tetraethoxysilane (TEOS). To immobilize the fluorescent reagent in the silica nanoparticles, rhodamine B ethanolic solution was added to the reacting mixture at different times (2; 3; 4 and 5 h) after starting the synthesis (which always lasts 7 h). The nanosensor obtained with the addition of rhodamine B after 5 h of synthesis showed the best sensitivity, measured as the fluorescence quenching, which was proportional to Cu(ii) ion. The nanosensor was selective to Cu(ii) ions and showed a linear range from 2.0 to 12.0 μmol L-1, detection limit of 0.40 μmol L-1, quantification limit of 1.3 μmol L-1, response time of 50 s, being possible to be reused 3 times. The nanosensor was applied to the determination of Cu(ii) in sugar cane spirit and the results obtained did not show significant differences from those obtained by atomic absorption spectrometry at a confidence level of 95%.

Why Can Water Droplets Move Smoothly Even on Statically Hydrophilic Surfaces?

Studies on hydrophilic surfaces showing excellent water sliding properties are very rare, despite the numerous practical advantages they offer. One of the authors has recently developed a smooth, transparent and sufficiently-thick hydrophilic film with low contact angle hysteresis (5°) and small water tilt angles (6 ± 2°) through a simple sol-gel reaction of 2-[methoxy (ethyleneoxy)10propyl]trimethoxysilane (PEG-M) and tetraethoxysilane (TEOS). However, the origins of these unusual water sliding properties have not been clearly identified. As such, the impact of the addition of TEOS acting as a "nanospacer" or the identity of PEG terminal functional groups on the final static/dynamic wetting properties needs to be explored. In this study, we investigated the orientational/conformational states of PEG chains in PEG-M/TEOS and [hydroxy(ethyleneoxy)8-12propyl]triethoxysilane (PEG-OH)/TEOS hybrid films under wet and dry conditions using sum-frequency generation (SFG) spectroscopy. We found that PEG-M/TEOS hybrid film surfaces had no marked differences in the conformational states of PEG chains under wet or dry conditions, resulting in excellent water sliding properties as there was no energy barrier for water droplet motion. In contrast, PEG chains were completely disordered after contact with water in the PEG-OH/TEOS hybrid films due to hydration effects. This large conformational change between the liquid/solid and gas/solid interface at the three-phase contact line resulted in an unfavorable energetic barrier for water droplet motion, leading to the poor water sliding properties. TEOS did not physically work as a "nanospacer," but chemically worked as a binder to endow practically useful properties, such as good adhesion and versatility in substrates used, to our hybrid films.

Improving the Fungus Resistance of Polymer Composites

The problem under consideration is the fungus resistance of polymeric construction composites and their components: epoxy and polyester binders, as well as mineral waste in the form of dust from electric precipitators and metallurgical slag. It has been found that epoxy and polyester binders in unfilled and fully hardened state are not fungus resistant. But polymer composites completely filled both with mineral waste and mentioned above binders proved to be fungus resistant. It has been confirmed that the fungus resistance of polymer composites is determined both by the type of the binder and the type of the filler. To increase the fungus resistance of epoxy and polyester composites, the use of microadditives of tetraethoxysilane and Irganox 1010 has been proposed. It has been established that the addition of tetraethoxysilane and Irganox 1010 promotes the increase in fungus resistance of epoxy and polyester composites.

Temperature and pH Responsive Janus Silica Nanoplates Prepared by the Sol-Gel Process and Postmodification.

During the process of emulsifying and hydrolyzing, reactive poly(3-(triethoxysilyl)propyl methacrylate)-b-polystyrene (PTEPM-b-PS) diblock copolymers can self-assemble and become cross-linked to form hollow spheres in situ with polystyrene on their inner surfaces. The addition of tetraethoxysilane (TEOS), which was hydrolyzed and condensed together with PTEPM block, can make those spheres as soft foldable capsules or hard hollow spheres depending on the amount of added TESO. Then postmodification, the surface-initiated Atom Transfer Radical Polymerization (ATRP) was applied to afford stimuli-responsive spheres, and the corresponding responsive Janus nanoplates (RJPs) were finally obtained by crushing those responsive hollow spheres (HSs) showing smart tunable emulsifiability and great potential in oily water purification. This facile method to fabricate HSs and RJPs could be used for preparing different Janus polymer-inorganic capsules and nanoplates with varied functions by changing the chemical composition of copolymer surfactants as well as the postmodification process.

Poly(lactic acid)/Functionalized Silica Hybrids by Reactive Extrusion: Thermal, Rheological, and Degradation Behavior

In the present work, poly(lactic acid) (PLA)/functionalized silica hybrids were prepared via reactive extrusion and their thermal, rheological, and degradation properties were investigated. The PLA was blended through reactive extrusion with functionalized silica, where silica network was formed by grafting-condensation reaction with tetraethoxysilane (TEOS) and (3-glycidyloxypropyl) trimethoxy-silane. The chemical structure and morphology were investigated by Fourier-transform infrared spectra, energy dispersive X-ray spectroscope and field-emission scanning electron microscope. Also, thermal, rheological properties and degradation behavior were measured. The glass transition temperature of the hybrids tended to decrease with increasing TEOS contents, while the degrees of crystallinity increased to about 57% according to TEOS contents. The complex viscosity and storage modulus of PLA/silica hybrids were enhanced clearly compared to that of neat PLA. While the molecular weight of pure PLA was decreased about 12% during processing, the decrease was smaller as less than 10% by the addition of TEOS. The η0 (zero-shear rate viscosity) using the Cross model was more than doubled by introducing TEOS. The resistance of hydrolysis was also improved as a result of the addition of silica network. In conclusion, the hybridization of PLA and silica network influenced the thermal and rheological properties, by which it may be possible to apply for various manufacturing process such as foam molding and blow molding, etc.

Antireflective coating based on TiO2 nanoparticles modified with coupling agents via acid-catalyzed sol-gel method

TiO2 – based materials were synthesized via acid-catalyzed sol-gel method using tetraethoxysilane (TEOS) and/or methyltriethoxysilane (MTES) - as silane coupling agents. The physical and chemical properties of the obtained TiO2 – based materials were characterized through FT-IR and UV–Vis spectroscopy, TGA, AFM analysis and contact angle measurements. FT-IR spectra demonstrated that the silane coupling agents react via a cross-link and covalently bond on the TiO2 surface. TGA analysis of samples was used to investigate the effect of addition of silane precursor into the TiO2 matrix. Diffuse reflectance spectra revealed that the addition of silane agents improved the antireflective properties of obtained thin films. Water contact angle of TiO2 - based materials showed that the wettability of the thin films was influenced by the addition of TEOS and/or MTES during the modification process. AFM images showed smooth surfaces (RMS roughness up to 3 nm) but with morphological peculiarities depending on the chemical modification, with TEOS, MTES or both, of the TiO2 parental matrix. Transparent and hydrophobic coatings were obtained with MTES addition in the modification process of TiO2 nanoparticles via acid-catalyzed sol-gel method.

Effect of Temperature on Annealing Products of Synthesized Opal Matrices

In this paper, we describe the synthesis of opal matrices by the sol-gel method and the α-cristobalite production from them by high-temperature annealing. Both the conditions for preparing synthetic opal matrices by the hydrolysis of tetraethoxysilane in a binary ethanol-water solvent using an ammonia solution as a catalyst and the reagent concentrations for this process are described in detail. The silica particles were prepared by multistage growth to the required size at addition of tetraethoxysilane to the reaction mixture. A temperature regime for drying the siliceous xerogel with the production of porous matrices for further use and annealing to obtain high-purity α-cristobalite is proposed. Structural adjustments, such as an increase in the matrix density, their hardening, and a temperature-dependent change in the matrix porosity, are described. Open-pore matrices consisting of amorphous silicon dioxide are prepared by annealing up to 1100°C. The prepared matrices can later be used for their impregnation with various compositions to obtain various types of sensors, composite materials, and inverted matrices. The transition of a silica xerogel from an amorphous state to a crystalline state with the formation of low-temperature α-cristobalite with an α-tridymite admixture by drying and annealing at 1300°C is shown. Further annealing at 1650°C leads to the formation of a transparent nonporous sample of α-cristobalite. All processes were performed under the control of scanning electron microscopy, Raman spectroscopy, and X-ray diffraction analysis.

Composite Fibers Based on Cellulose and Tetraetoxysilane: Preparation, Structure and Properties

A method for producing cellulose-based composite fibers with the addition of tetraethoxysilane (TEOS) with a high degree of dispersion of the additive in the cellulose matrix through a “solid phase” dissolution step of the cellulose in N-methylmorpholine-N-oxide (NMMO) is proposed. Investigation of the phase state and morphological features of mixtures of cellulose solutions with TEOS additives in NMMO has shown that in the entire range of concentrations studied, the solutions are biphasic emulsions, and their dispersity and the shape of dispersed phase droplets depend on the prehistory of solution preparation. It is established that the rheological behavior of cellulose solutions with TEOS additives varies depending on the amount of the additive. A theory about a mechanism for changing the rheological behavior of cellulose solutions with TEOS is formulated. X-ray diffraction analysis, scanning and transmission microscopy and IR spectroscopy were used to characterize the structure and morphology of composite fibers. The mechanical properties of composite cellulose fibers with TEOS are investigated.

Aggregate stability and magnetic characteristics of colloidal Fe m O n –SiO2 particles obtained by sol–gel method

Composite FemOn–SiO2 particles have been obtained by precipitation of iron oxide from aqueous solution with the addition of tetraethoxysilane. The shapes and sizes of separate single particles and their aggregates have been determined by scanning electron microscopy. Changes in the stability of the colloidal suspension due to external magnetic field and the addition of NaCl have been evaluated. Based on magnetization curves obtained on a vibrating-sample magnetometer and characteristics calculated within the theoretical model of magnetostatically interacting particles, it is shown that the composite particles are superparamagnetic.

Hybrid Coatings Enriched with Tetraethoxysilane for Corrosion Mitigation of Hot-Dip Galvanized Steel in Chloride Contaminated Simulated Concrete Pore Solutions.

Hybrid sol-gel coatings, named U(X):TEOS, based on ureasilicate matrices (U(X)) enriched with tetraethoxysilane (TEOS), were synthesized. The influence of TEOS addition was studied on both the structure of the hybrid sol-gel films as well as on the electrochemical properties. The effect of TEOS on the structure of the hybrid sol-gel films was investigated by solid state Nuclear Magnetic Resonance. The dielectric properties of the different materials were investigated by electrochemical impedance spectroscopy. The corrosion behavior of the hybrid coatings on HDGS was studied in chloride-contaminated simulated concrete pore solutions (SCPS) by polarization resistance measurements. The roughness of the HDGS coated with hybrids was also characterized by atomic force microscopy. The structural characterization of the hybrid materials proved the effective reaction between Jeffamine® and 3-isocyanate propyltriethoxysilane (ICPTES) and indicated that the addition of TEOS does not seem to affect the organic structure or to increase the degree of condensation of the hybrid materials. Despite the apparent lack of influence on the hybrids architecture, the polarization resistance measurements confirmed that TEOS addition improves the corrosion resistance of the hybrid coatings (U(X):TEOS) in chloride-contaminated SCPS when compared to samples prepared without any TEOS (U(X)). This behavior could be related to the decrease in roughness of the hybrid coatings (due TEOS addition) and to the different metal coating interaction resulting from the increase of the inorganic component in the hybrid matrix.

Pore Clogging of Colloidal Mesoporous Silica Nanoparticles for Encapsulating Guest Species

Abstract Colloidal mesoporous silica nanoparticles (CMS) are useful as carriers for imaging probes because of their unique features. A simple method for the pore clogging of CMS has been proved by the addition of tetraethoxysilane under weakly basic conditions. The pore clogging of CMS is useful for encapsulation of thermoresponsive dyes.

Chrysotile asbestos detoxification with a combined treatment of oxalic acid and silicates producing amorphous silica and biomaterial

This study was primarily imposed by the ever increasing need for detoxification of asbestos and asbestos containing materials (ACM), with potential application onsite. The present work investigates potential detoxification of pure chrysotile (Chr) asbestos via a combined treatment of oxalic acid dihydrate (Oxac) (Η2C2Ο4·2Η2Ο) with silicates, such as tetraethoxysilane (TEOS) (SiH20C8O4) and pure water glass (WG) (potassium silicate) (K2SiO3). These reagents used in the experimental procedure, do not cause adverse effects on the environment and are cost effective. The results of FTIR, XRD, optical and scanning microscopy coupled with EDS analyses indicated that all of the applied treatments destructed the Chr structure and yielded silica of amorphous phase and the biomaterial glushinskite from the Oxac reacted with brucite [Mg(OH)2] layer. Each of the proposed formulations can be applied for the detoxification of asbestos, according to priorities related to the specific products of the recovery treatment. Therefore, Oxac acid leaching followed by the TEOS addition is preferred in cases of glushinskite recovery; TEOS treatment of asbestos with subsequent Oxac addition produced amorphous silica production; finally Oxac acid leaching followed by WG encapsulated the asbestos fibers and can be used in cases of onsite asbestos and ACM detoxification.

Studies on Thermal and Mechanical Properties of Epoxy-Silicon Oxide Hybrid Materials

Ultrasonic dual mixing (UDM) process involving ultrasonic vibration with simultaneous stirring is used to prepare epoxy-silicon oxide hybrid materials with inorganic nanoscale building blocks by incorporating nanoscale silicon oxide network in epoxy matrix. The silicon oxide network is obtained from tetraethoxysilane (TEOS) by using the in situ sol-gel process. Same epoxy-silica hybrid materials were also prepared by mixing with simple impeller stirring, and its properties were compared with the material of same composition prepared by the UDM process. The epoxy-silicon oxide hybrid materials are characterized by using FT-IR, DSC, FESEM, and XRD techniques. The glass transition temperature, tensile strength, and elastic modulus of the epoxy-silicon oxide hybrid materials treated by UDM process are found comparatively better than those of the materials processed by a rotating impeller. FESEM studies confirm that amount of TEOS varies the distribution and size of silicon oxide network, which remains relatively finer at lower content of TEOS. Significant improvement of thermal and mechanical properties of the neat epoxy is noted in the presence of 3.05 wt.% TEOS content in it is giving rise to the formation of inorganic building block of silicon oxide of size 88 ± 45 nm in the matrix. In this regard, the use of UDM process is found superior to mixing by simple impeller stirring for enhancement of properties of epoxy-silicon oxide hybrid materials. Lowering of properties of the epoxy-silicon oxide hybrid materials with TEOS addition beyond 3.05 wt.% up to 6.1 wt.% occurs primarily due to increase of amount and size (up to 170 ± 82 nm) of the inorganic building block in the matrix.

Development of novel alginate–silica hybrid membranes for pervaporation dehydration of isopropanol

Using a sol–gel technique, organic–inorganic hybrid membranes were prepared by incorporating silica precursors into alginate matrix. Alginate was used as a starting organic polymer, whereas 3-aminopropyl triethoxysilane was used as a counter cation and precursor for the development of inorganic phase. The content of silica gel was controlled by the further addition of tetraethoxysilane (TEOS). The resulting membranes were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis. After measuring the swelling data at different mass% of water, membranes were subjected for the pervaporation separation of water–isopropanol mixtures in a temperature range of 30–60 °C. The experimental results demonstrated that membrane containing 30 mass% of TEOS showed the highest separation factor of 17,253 with flux of 4.42 × 10−2 kg/m2 h at 30 °C for 5 mass% of water. Except in pure alginate membrane, the values of total flux and flux of water are found to be almost overlapping, suggesting that the developed hybrid membranes could be effectively used to break the azeotropic point of water–isopropanol mixtures. From the temperature-dependent diffusion and permeation values, the Arrhenius activation parameters were estimated. The estimated E p and E D values were ranged between 27.84 and 32.63, and 26.98 and 31.28 kJ/mol, respectively. The positive heat of sorption (∆H s) values was observed in all the membranes, indicating that Henry’s mode of sorption is predominant.

Functionalized Magnetic Mesoporous Silica Nanoparticle‐Supported Palladium Catalysts for Carbonylative Sonogashira Coupling Reactions of Aryl Iodides

AbstractMagnetic mesoporous silica nanoparticles (MMSN) were prepared and used as a support for palladium catalysts. MMSN with a surface area of 1909 m2 g−1 were synthesized by a nanoemulsification process involving the dispersion of hydrophobic magnetite nanoparticles in chloroform in the presence of cetyltrimethylammonium bromide, followed by the addition of tetraethoxysilane and its polycondensation by a sol–gel route. The MMSN were modified with phosphine and N‐heterocyclic carbene‐based ligands, which provided coordination sites for conjugation with a palladium catalyst. These modified particles were fully characterized and employed as catalyst nanosupports. The palladium catalyst was immobilized on the surface and within the pores of MMSN and applied in copper‐free carbonylative Sonogashira coupling reactions of aryl iodides with terminal alkynes.

Syntheses of polyamine-bridged polysilsesquioxanes hybrid materials combining sol–gel processing and molecular imprinting applied to selective adsorption for copper

Bridged polysilsesquioxanes hybrid materials with Cu(II) recognition properties were synthesized by sol–gel method and imprinting techniques in this paper. Polyamine-bridged monomers containing soft long-chain organic bridge were used to synthesize these materials possessing high ligand densities and good selectivity for Cu(II). Three classes of Cu(II) imprinted materials were synthesized according to the following routes: (1) self-condensation of polyamine-bridged monomers, (2) co-condensation of tetraethoxysilane (TEOS) and polyamine-bridged monomer around supramolecular assemblies of hexadecyltrimethylammonium bromide (CTAB), and (3) co-condensation of TEOS, 3-aminopropyltriethoxysilane (APES) and polyamine-bridged monomers around CTAB. Adsorption tests showed that materials obtained with the addition of TEOS and CTAB exhibit an enhanced capacity as compared to the nonimprinted material for the adsorption of Cu(II). The addition of APES increased the content of functional groups and then improved the adsorption capability. Selective adsorption tests showed that materials had better selectivity for Cu(II) in the mixtures of Cu(II)–Ni(II), Cu(II)–Pb(II), Cu(II)–Cd(II) and Cu(II)–Zn(II), but poorer selectivity in Cu(II)–Hg(II) and Cu(II)–Ag(I) mixtures.

Regioselective Coating of Tetrapod-like Clusters with Silica

We describe an easy procedure to regioselectively coat binary tetrapod-like silica/polystyrene clusters with silica. First we show that the addition of tetraethoxysilane into a basic hydroalcoholic suspension of binary tetrapods induces the preferential growth of their silica core, which conforms to the shape of the polystyrene nodules while growing. On the contrary, we show that the formation of a continuous silica shell around the clusters is promoted if silanol groups have been incorporated at the surface of the polystyrene nodules before the addition of tetraethoxysilane. The thickness and the roughness of the silica coating can be tuned by varying several experimental parameters.

Hybrid films with (trimethoxysilylpropyl) methacrylate (TMSM), poly (methyl methacrylate) PMMA and tetraethoxysilane (TEOS) applied on tinplate

The tetraethoxysilane (TEOS) influences morphological and electrochemical properties of hybrid films by function of concentration. Moreover, the use of acetic acid as a catalyst in the sol enables a more complete hydrolysis of the silane precursors due to the fact that the acetic acid goes through a more complete ionization when in aqueous solution. The aim of this paper is to study the effect of the concentration of tetraethoxysilane (TEOS) on the protective properties of the film on tinplate substrate. The tinplate was coated with a hybrid film obtained from a sol-gel method constituted of the following alkoxide precursors: 3 - (trimetoxisililpropil) methacrylate (TMSM) and poly(methyl methacrylate) PMMA. The effect of tetraethoxysilane (TEOS) concentration has also been evaluated. The films hydrolysis was performed at a pH value of 3. 0 using acetic acid as a catalyst. The films were obtained by dip-coating process, cured for 3 hours at 160 ºC. The film morphology was evaluated by SEM and profilometry. The electrochemical behavior of the films was evaluated by open circuit potential monitoring, potentiodynamic polarization and electrochemical impedance spectroscopy. The film hydrophobicity was determined by contact angle measurements. The studied films have shown good performance as to corrosion resistance on tinplate. The hybrid film which was obtained through the addition of an excessive amount of TEOS (T3A3) showed increased thickness. Nevertheless, due to an intense densification of the film, promoted by the addition of TEOS, a formation of cracks was registered, thereby compromising the corrosion resistance.