Methyltriethoxysilane Research Articles

Fabrication of single-layer antireflective coating with environmental stability by modified SiO2 mixed sol

The single-layer antireflective coating (ARC) is fabricated by sol-gel method using mixed sol modified by methyltriethoxysilane (MTES) hydrolyzed sol. The surface morphologies and structure, optical properties and wetting behavior are affected by the amount of MTES hydrolyzed sol are investigated. Via dip coating the modified sol on glass substrates, environmental stability and mechanical properties are also examined. In the modification process, the ARC exhibits a hydrophobic surface with a highest water contact angle (WCA) of 126.53°. Sand adhered to coating could be easily washed away, confirming that the ARC exhibits prominent self-cleaning property. Moreover, the ARC appears excellent in environmental stability. After the 30-day damp test and self-cleaning test, the attenuation of solar-weighted transmittance (Тsw) is only 0.04% and 0.02%, respectively. Additionally, this ARC exhibits a total solar-weighted transmittance (Тsw) higher than 95.06% over a wavelength range of 380–1100 nm, significantly higher than those of bare glass substrates (Тsw=91.5%). The ARC has highly promising applicability in the solar fields.

Preparation and characterization of building insulation material based on SiO2 aerogel and its composite with expanded perlite

This article aims to complement the advantages of SiO2 aerogel and expanded perlite (EP) to prepare high-performance building insulation materials. SiO2 aerogels were prepared via acid/base two-step catalytic process followed by ambient pressure drying (APD) process. The two-step surface modification method is used to improve hydrophobicity of aerogel. And SiO2 aerogel/EP thermal insulation composites were obtained via introducing wet gel into EP. The effects of the amount of water, the amount of anhydrous alcohol and the pH value of sol on the properties of aerogels were analyzed. And the effects of vacuum degree and adsorption time on the thermal conductivity and compressive strength of SiO2/EP composite were studied. The pore size distribution and chemical structure of SiO2 aerogel were characterized by N2 adsorption-desorption test and Fourier transform infrared spectroscopy (FTIR). The micromorphology, crystal structure of SiO2 aerogel and SiO2/EP composite were characterized by scanning electron microscope, X-Ray diffraction. The results show that the thermal conductivity of SiO2 aerogel prepared with tetraethoxysilane (TEOS): methyltriethoxysilane (MTES): ethanol (EtOH):H2O = 1:0.3:14:6 (mole ratio) was as low as 0.0212 W/(m·K), the aerogel had high porosity (95.05%) and super hydrophobicity(the contact angle is 158.7°). Meanwhile, it was found that SiO2 aerogel is stably distributed in the pores of the EP and effectively reduces its thermal conductivity and water absorption. The minimum thermal conductivity of SiO2/EP composite was 0.036 W/(m·K), the minimum water absorption was 9.2% and the compressive strength was 214.35 kPa. Hence, SiO2 aerogel/EP with good performance and low cost has great potential in the field of building insulation.

Multiple Intermolecular Interaction to Improve the Abrasion Resistance and Wet Skid Resistance of Eucommia Ulmoides Gum/Styrene Butadiene Rubber Composite.

A rubber composite was prepared by using methyltriethoxysilane (MTES) to modify silica (SiO2) and epoxidized eucommia ulmoides gum (EEUG) as rubber additives to endow silica with excellent dispersion and interfacial compatibility under the action of processing shear. The results showed that compared with the unmodified silica-reinforced rubber composite (SiO2/EUG/SBR), the bound rubber content of MTES-SiO2/EEUG/EUG/SBR was increased by 184%, and its tensile strength, modulus at 100% strain, modulus at 300% strain, and tear strength increased by 42.1%, 88.5%, 130.8%, and 39.9%, respectively. The Akron abrasion volume of the MTES-SiO2/EEUG/EUG/SBR composite decreased by 50.9%, and the wet friction coefficient increased by 43.2%. The wear resistance and wet skid resistance of the rubber composite were significantly improved.

Cobalt-Doped Silica Organic-Inorganic Materials by Sol-Gel Method: Preparation and Thermal Stability Calcined under N2 Atmosphere

Cobalt-doped silica organic-inorganic (Co/SiO2) materials were prepared by sol-gel technique using tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) as silicon precursors and Co(NO3)2·6H2O as cobalt source. The influence of calcination temperature on the microstructure of Co/SiO2 material under N2 atmosphere was discussed by X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy dispersive spectrum (EDS) and thermogravimetric-differential thermogravimetric (TG-DTG) measurements. The results showed that, when calcined at N2 atmosphere, the Co element in the Co/SiO2 material exists not only as the Si-O-Co bond, but also the crystals containing the cobalt element. In the calcing process of 25 ∼ 800 °C, the crystals containing the cobalt element have successively undergone four phase transitions from Co(NO3)2·6H2O to Co3O4, CoO and elemental Co0. The Si-O-Co bonds were formed in the calcined Co/SiO2 materials. The water contact angle on the Co/SiO2 film surface achieved the maximum value of 95.6° when the calcination temperature is at 400 °C. In order to keep the hydrophobicity of Co/SiO2 membrane materials for gas separation, the optimal calcination temperature should be 350 ∼ 400 °C. The Co/SiO2 membrane material calcined at 400 °C has a larger specific surface area, pore volume and mean pore diameter than the SiO2 sample.

Physicochemical Characterization and Drug Release Properties of Methyl-Substituted Silica Xerogels Made Using Sol-Gel Process.

In this work, a multi-analytical approach involving nitrogen porosimetry, small angle neutron and X-ray scattering, Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies, X-ray diffraction, thermal analysis and electron microscopy was applied to organically modified silica-based xerogels obtained through the sol–gel process. Starting from a tetraethoxysilane (TEOS) precursor, methyltriethoxysilane (MTES) was added to the reaction mixture at two different pH values (2.0 and 4.5) producing hybrid xerogels with different TEOS/MTES molar ratios. Significant differences in the structure were revealed in terms of the chemical composition of the silica network, hydrophilic/hydrophobic profile, particle dimension, pore shape/size and surface characteristics. The combined use of structural characterization methods allowed us to reveal a relation between the cavity dimensions, the synthesis pH value and the grade of methyl substitution. The effect of the structural properties on the controlled Captopril release efficiency has also been tested. This knowledge facilitates tailoring the pore network for specific usage in biological/medical applications. Knowledge on structural aspects, as reported in this work, represents a key starting point for the production of high-performance silica-based hybrid materials showing enhanced efficacy compared to bare silica prepared using only TEOS.

Hydrophobic silica films derived from methyltriethoxysilane (MTES): Effect of pH and calcination temperature

Hydrophobic silica films derived from methyltriethoxysilane (MTES): Effect of pH and calcination temperature

Effect of hybrid aluminum dihydrogen phosphate on the corrosion resistance of PTFE composite ceramic coatings

AbstractIn this study, the polytetrafluoroethylene (PTFE) composite ceramic coatings with hybrid aluminum dihydrogen phosphate (AP) are prepared on AISI 304L stainless steel by spraying and heat curing to improve the corrosion resistance of the coatings. AP is hybridized with methyltriethoxysilane (MTES), and the structure of the hybrid AP is characterized by Fourier‐transform infrared spectroscopy and X‐ray photoelectron spectroscopy. Contact angle tests, scratch tests, and electrochemical experiments are used to investigate the corrosion behavior of composite ceramic coatings. In addition, scanning electron microscopy is used to examine the microscopic morphology of the coatings after corrosion to investigate the mechanism of the hybrid AP on the corrosion resistance of the composite ceramic coatings. The findings reveal that MTES successfully hybridizes with AP and implants the –CH3 hydrophobic group in AP, which improves the hydrophobicity of composite coatings. The corrosion potential of hybrid AP coatings all move in a positive direction, and the corrosion current density is lower than that of unhybridized AP coatings. The corrosion current density of the coating is about 2.931e−008 A/cm2 when the MTES content is 5 wt%, which is 20% less than that of the unhybridized AP coating. Results indicate hybrid AP can significantly improve the corrosion resistance of PTFE composite ceramic coatings with the best corrosion resistance occurring when the content of MTES is 5 wt%.

Impact of hydrophilic polymers in organosilica matrices on structure, stability, and biocatalytic activity of immobilized methylotrophic yeast used as biofilter bed

The impact of hydrophilic polymers in an organosilica matrix on the features and performance of immobilized methylotrophic yeast cells used as biocatalysts was investigated and described. Yeast cells were immobilized in a matrix made of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) by one-step sol-gel route of synthesis in the presence of polyethylene glycol (PEG) or polyvinyl alcohol (PVA). Organosilica shells were spontaneously built around cells as a result of yeast immobilization at a TEOS to MTES ratio of 85/15 vol% and hydrophilic polymer (PEG or PVA). As a structure-directing agent, PVA produces organosilica films. Stable high-performance biocatalysts active for one year, if stored at −18 °C, have been obtained by entrapment of methylotrophic yeast cells. A trickling biofilter with and without active aeration was designed using entrapped yeast cells to treat methanol polluted wastewater. A biofilter model with active aeration could halve methanol input thus demonstrating better performance compared to treatment without active aeration.

A superhydrophobic and flame-retardant cotton fabric fabricated by an eco-friendly assembling method

A novel eco-friendly and durable superhydrophobic and flame-retardant cotton fabric with fluorine-free, halogen-free was prepared via step-by-step dip-coating and spraying technology. At first, common cotton fabric was impregnated in the flame-retardant ethoxysilane-terminated phosphate polyurethane. Afterwards, methanol mixture containing silica nanoparticles, methyl triethoxysilane, and dihydroxy-terminated polydimethylsiloxane was sprayed on the surface of the cotton fabric. Finally, a flame-retardant cotton fabric with micro-nano rough surface and low surface energy was formed. The resulting superhydrophobic and flame-retardant cotton fabric exhibited superamphiphobicity with the contact angle and sliding angle of 160° and 6°, respectively, while flame retardancy with limited oxygen index of 28.1%. and flame self-extinguishing. Furthermore, this superhydrophobic and flame-retardant cotton fabric showed robust superhydrophobicity and flame-retardancy after undergoing 1000 cycles of abrasion, 60 min of ultrasonic washing and 50 standard machine washing cycles, in sequence, indicating its potential as a multifunctional protective textile fabric. Additionally, the method proposed in this study can effectively solve durability and environmental problems currently faced by the coated fabric with superhydrophobicity and flame-retardancy.

Controlled release of molasses melanoidin-like product from hybrid organic-inorganic silica xerogels and its application to the phytoextraction of lead through the Indian mustard.

In this study, we investigate the release of melanoidin-like product (MLP) from hybrid silica xerogels to control the quantity of MLP in the medium for lead phytoextraction. In the preparation of the hybrid organic-inorganic xerogels with MLP, tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), propyltriethoxysilane (PTES), and 3-aminopropyltriethoxysilane (APTES) were used as precursors. The experimental results suggest that the release of MLP can be easily controlled by partially substituting TEOS with the organosilanes. The addition of the organosilanes lowered the release rate of MLP in the following order of xerogels: TEOS, MTES/TEOS, PTES/TEOS, and APTES/TEOS. Furthermore, a novel phytoextraction of lead through the Indian mustard was conducted using the MLP-doped TEOS xerogel. Results show that the addition of TEOS xerogel did not have any influence on the growth of the mustard, whereas the lead uptake significantly increased in a nutrition medium with 1-mM Pb(NO3)2. In conclusion, the beneficial effect of the MLP-doped TEOS xerogel on lead phytoextraction was confirmed.

Layer-by-Layer Deposited Hybrid Polymer Coatings Based on Polysaccharides and Zwitterionic Silanes with Marine Antifouling Properties.

Polyelectrolyte multilayer (PEM) assembly is a versatile tool to construct low-fouling coatings. For application in the marine environment, their structure needs to be stabilized by covalent linkage. Here, we introduce an approach for spin coating of silane-based sol-gel chemistries using layer-by-layer assembly of polysaccharide-based hybrid polymer coatings (LBLHPs). The silane sol-gel chemistry allows the films to be cross-linked under water-based and mild reaction conditions. Two different silanes were used for this purpose, a conventional triethoxymethyl silane and a de novo synthesized zwitterionic silane. The polysaccharide-silane hybrid polymer coatings were thoroughly characterized with spectroscopic ellipsometry, water contact angle (WCA) goniometry, attenuated total reflection-Fourier transform infrared spectroscopy, and atomic force microscopy. The coatings showed good stability in seawater, smooth surfaces, a high degree of hydration, and WCAs below or close to the Berg limit. LBLHPs showed low-fouling properties in biological assays against nonspecific protein adsorption, attachment of the diatom Navicula perminuta, and settlement of zoospores of the macroalga Ulva linza.

Mesoporous Methyl-Functionalized Titanosilicate Produced by Aerosol Process for the Catalytic Epoxidation of Olefins

Titanosilicates (Ti-SiO2) are well-known catalysts for the epoxidation of olefins. Isolated Ti inserted in the silica framework in tetrahedral coordination are the active species. Recently, adjusting the hydrophobic/hydrophilic balance of such catalysts’ surfaces has appeared as a promising tool to further boost their performance. However, adjusting the hydrophobic/hydrophilic balance via a one-pot classical sol-gel generally leads to a decrease in the Ti dispersion and/or collapse of the pore network. To overcome this limitation, hydrophobic mesoporous Ti-SiO2 were here synthesized by aerosol-assisted one-pot sol–gel, which allowed the simultaneous control of their Ti loading, degree of methyl-functionalization, and textural properties. Methyl-functionalization was achieved by a partial substitution of tetraethoxy silane (TEOS) by methyltriethoxy silane (MTES) in different ratios. Solid-state 29Si-NMR, FTIR, TGA, and vapor-phase water adsorption showed that methyl moieties were effectively incorporated, conferring a hydrophobic property to the Ti-SiO2 catalysts. ICP-AES, DRUV, XPS, and N2 physisorption demonstrated that Ti dispersion and textural properties were both successfully preserved upon the incorporation of the methyl moieties. In the epoxidation of cyclooctene with tert-butyl hydroperoxide as oxidant, the hydrophobic Ti-SiO2 showed higher catalytic performance than pristine Ti-SiO2 prepared without MTES. In addition to disentangling the positive effect of adjusting the hydrophobic/hydrophilic balance of epoxidation catalysts on their performance, this contribution highlights the advantages of the aerosol procedure to synthesize mesoporous functionalized catalysts with very high dispersion of active sites.

Transparent hydrophobic thermal insulation CsxWO3-ZnO-SiO2 coatings:Energy saving, anti-dust and anti-fogging performance

CsxWO3-ZnO-SiO2 smart coatings were proposed to achieve multiple functions, such as thermal insulation, anti-dust, anti-fogging and blocking harmful ultraviolet light, etc. The transparent hydrophobic hybrid resins were prepared from methyltriethoxysilane (MTES) and SiO2 sol, which was used as the substrate of the composite coating. The CsxWO3 is served as the near-infrared (NIR) absorber, and the ZnO is functioned as the ultraviolet (UV) blocking agent. Coatings with different ratios of CsxWO3 and ZnO were successfully prepared by co-blending with nano-SiO2 resin. The morphology, microstructure, surface composition, hydrophobicity, thermal stability, anti-dust and optical property of the composite coatings were investigated comprehensively. The transmittance of C10Z10 (CsxWO3 10%, ZnO 10%, nano-SiO2 resin 80%) coating at 370 nm is 2.3%, and the value of Solar Energy Transmittance Selectivity (SETS) is 0.665, which exhibits excellent NIR shielding ability. Compared with nano-SiO2 resin coating, the thermal insulation temperature difference can reach 7.0 °C. The C10Z10 coating showed good durability in the twenty times anti-dust repeated tests and the efficiency could maintain 70.3% after the repeating tests. The coating showed excellent sustainability after a 45-day outdoor exposure experiment and a 240 h of artificial accelerated aging experiment. Thus, the proposed CsxWO3-ZnO-SiO2 coatings are promising for outdoor smart windows.

PREPARATION AND CHARACTERIZATION OF MAGNESIUM/ALUMINIUM LAYERED DOUBLE HYDROXIDE AS FILLER IN LOW-DENSITY POLYETHYLENE COMPOSITE

Polymer had been widely used in industries nowadays. However, the properties of the polymer itself are limited to a particular application. This study describes synthetic clay, layered double hydroxide (LDH), as a filler in low-density polyethylene (LDPE) composite. LDHs of magnesium/aluminium-dodecyl sulfate (Mg/Al-DS) and its grafted with triethoxymethylsilane (TEMS), (TEMS-g-Mg/Al-DS) were synthesized through co-precipitation and salinization reaction methods. The presence of alkyl group, v(C-H) in both LDH had confirmed through Fourier transform infrared (FTIR). The appearance of peaks in FTIR spectra within the absorbance range of 2800 – 2930 cm-1 indicates a successful surface modification of LDH, supported by the changes of interlayer spacing and the presence of carbon from X-ray diffractogram and CHNS elemental analysis, respectively. The synthesized LDH was mixed with LDPE via melt intercalation method. The LDH modification resulted in higher interaction and compatibility between the LDPE matrix and LDH by the formation exfoliated type of nanocomposites, as suggested by XRD analysis.

Resistance to Growth of Molds for Wood Modified with Hydrophobic Hybrid Silica Gel Containing Copper Amine Complexes.

Complexation copper with amine provides an effective strategy for fixation copper in wood, while hydrophobic modification improves the dimensional stability of wood. Thus, a combination of complexation and hydrophobization is expected to enhance the efficiency of copper-based biocides. In this study, hydrophobic hybrid silica gel containing copper amine complexes (MACu) was prepared through an in situ sol-gel process in wood using methyltriethoxysilane (MTES), 3-amino-propyltriethoxysilane (APTES), and copper chloride. The resistance to growth of molds for MACu modified wood (Populus tomentosa) was measured according to ASTM D3273-16. A leaching resistance test was carried out in accordance with AWPA E11-16. The results showed that only Aspergillus niger covered the surface of untreated wood blocks and no mold grew on the MACu surface even after the leaching test. MACu xerogel and MACu wood were further characterized by SEM-EDS, FTIR, and XPS. A possible schematic diagram of the reaction mechanism was proposed to explain the high-efficiency anti-mold performance of MACu wood.

Revisiting the System Silanes-Polysaccharides: The Cases of THEOS-Chitosan and MeTHEOS-Chitosan.

The glycol alkoxysilanes, tetrakis(2-hydroxyethyl)silane (THEOS), and tris(2-hydroxyethyl)methyl silane (MeTHEOS) are water soluble derivatives of tetraethoxysilane (TEOS) and methyltriethoxysilane (MeTEOS) and precursors of the system silane-chitosan reviewed in this work. The glycol modified alkoxysilanes are obtained by transesterification reaction of TEOS or MeTEOS with ethylene glycol. The reaction evolution is monitored by 29 Si NMR. It is possible to observe the formation of the various species of glycol alkoxysilanes in equilibrium as the reaction proceeds showing that the oligomers formation is favored at longer reaction times with the final product tendency to gel keeping the complete water solubility. The glycol alkoxysilanes are synthesized at moderated reaction conditions, by using the Piers-Rubinsztajn (PR) reaction. Additionally, it is already known that THEOS is compatible with different natural polysaccharides as chitosan and the same behavior has been demonstrated in this work for MeTHEOS. Several reports refer studies regarding the system THEOS-polysaccharides to synthesize hybrid materials. The system THEOS-chitosan is known but the characterization as well as the way silane-chitosan interact has not been studied in detail. In the present report, chemical evidence of the covalent interactions THEOS- and MeTHEOS-chitosan based on NMR studies (13 C and 29 Si) are presented as intended.

BIOHYBRID MATERIALS AS PROMISING BIOCATALYSTS IN THE DEVELOPMENT OF BIOFILTERS FOR THE METHANOL WASTEWATER TREATMENT

Yeast cells were immobilized in a matrix made of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) by one-step sol-gel route of synthesis in the presence of polyethylene glycol (PEG) or polyvinyl alcohol (PVA). . A trickling biofilter with and without active aeration was designed using entrapped yeast cells to treat methanol polluted wastewater.

Study of Crystallization and Composition on Silicon Oxycarbide (SiOC) and Silicon Boron Oxycarbide (SiBOC) Ceramics Obtained from Alkoxysilanes Precursors

This work deals on the preparation of silicon oxycarbide (SiOC) and silicon boron oxycarbide (SiBOC) ceramics from pyrolysis involving alkoxysilanes with different organic groups. Boron content, organic substituent and annealing time were evaluated on crystallization and composition of resulting ceramics. B-free precursors composed of methyltriethoxysilane (MTES), phenyltriethoxysilane (PTES) and vinyltrimethoxysilane (VTMS) were obtained by the sol-gel method, whilst B-containing precursors were prepared by adding to each alkoxysilane a proper amount of boric acid resulting in B/Si atomic ratios of 0.1 and 0.5. Precursors were pyrolyzed at 1500 °C for 1 and 3 h to produce respective SiOC and SiBOC ceramics. X-ray diffraction (XRD) patterns revealed enhanced SiC phase crystallization for PTES-derived ceramics, followed by those containing vinyl and methyl groups, which was also confirmed by X-ray photoelectron spectroscopy (XPS) from percentages of Si-C and Si-O bonds. Csp2 and Csp3 amounts varied among ceramics, indicating direct influence of organic substituent on conductive carbon phase development. Boron addition induced the growth of SiC crystallites, having more evident effect in matrices with higher proportions of amorphous fraction and lower residual carbon amounts. Organic group nature, boron content and annealing time played an important role for production and evolution of SiC and C phases into ceramics.

Rapid synthesis of dual-mesoporous silica aerogel with excellent adsorption capacity and ultra-low thermal conductivity

In this paper, using methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) as co-precursor, dual-mesoporous silica aerogel was rapidly prepared within 20 h by ambient pressure drying. The dual-mesoporous structure can be obtained just by control the amount of TEOS. The skeleton structure of the dual-mesoporous aerogel is composed of small mesopores (3-6 nm) and large mesopores (17-30 nm). Moreover, the thermal conductivity (as low as 0.0223 W/(mK)) of the dual-mesoporous aerogel is much lower than most of MTES-based aerogels. More importantly, the obtained dual-mesoporous aerogel can separate oil from surfactant-stabilized oil-in-water emulsion, the separation efficiency as high as 97.6%. In addition, the aerogel exhibits superhydrophobic with a contact angle of 157.4°, thermally stable reaching up to 489.5°C and outstanding sorption capacity reaching up to 8.4-17.1 g/g. The dual-mesoporous silica aerogel have potential application in thermal insulating and organic pollutants sorption.

Preparation and characterization of hydrophobic coatings on wood surfaces by a sol-gel method and post-aging heat treatment

To improve the hydrophobicity and moisture resistance of wood, a hydrophobic coating using tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) as precursors was prepared on a wood surface via sol–gel and post-aging heat treatment. The effects of the MTES/TEOS molar ratio and aging heat treatment temperature on the properties of the MTES/TEOS coatings based on a co-precursor (M/T-based) were analyzed. The coating structures were analyzed by Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analyzer. The results indicated that a higher MTES/TEOS molar ratio increased the hydrophobicity of the coatings because of a higher silica content or a higher coverage of the surface by methyl groups. However, the hydrolysis-condensation reaction of TEOS decreased when an excessive amount of MTES was used, decreasing the hydrophobicity of the coating. Moreover, with an increase in aging heat treatment temperature, the coated wood improved its resistance to wetting; however, the stability of the M/T-based sol decreased, and the particles agglomerated. Thermogravimetric analysis/infrared spectrometry results showed that the coatings exhibited good heat resistance and enhanced the thermal stability of the wood. Adhesion testing results indicated that the coatings exhibited good adhesion to the wood substrates.