Functional Alkoxysilanes Research Articles

Investigations on the Impact of a Series of Alkoxysilane Precursors on the Structure, Morphology and Wettability of an Established Zirconium-Modified Hybrid Anticorrosion Sol-Gel Coating.

The current study reports on the impact of a series of functional alkoxysilanes on the wettability and structure of a well-established silicon/zirconium hybrid anticorrosion sol-gel coating. The selected functional alkoxysilanes comprise tetra ethylorthosilicate (TEOS), 3-glycidyloxypropyltrimethoxysilane (GPTMS), 3-aminopropyltriethoxysilane (APTES) and vinyltriethoxysilane (VTES) and are incorporated at various concentrations (1, 5, 10 and 20%) within the silicon/zirconium sol-gel material. The prepared materials are successfully processed as coatings and cured at different temperatures in the range of 100-150 °C. The characterisation of the structures and surfaces is performed by dynamic light scattering (DLS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), silicon nuclear magnetic resonance spectroscopy (29Si-NMR), atomic force microscopy (AFM) and static water contact angle (WCA). Structural characterisations (DLS, FTIR,29Si-NMR) show that the functional alkoxysilanes effectively bind at the surface of the reference sol-gel material, resulting in the formation of functional core-shell nanoparticles. WCA results show that the hydrophobic properties of all materials decrease with curing temperature, and AFM analysis demonstrated that this behaviour is associated with a decrease in roughness. The physico-chemical processes taking place are critically assigned and discussed.

New Functional Alkoxysilanes and Silatranes: Synthesis, Structure, Properties, and Possible Applications.

The aza-Michael reaction of 3-aminopropyltriethoxysilane (1) and -silatrane (2) with acrylates affords functionalized silyl-(3-8) and silatranyl-(9-14) mono- and diadducts with up to a 99% yield. Their structure has been proved with IR and NMR spectroscopies, mass spectrometry and XRD analysis. The hydrolytic homo-condensation of triethoxysilanes 3-5 gives siloxanes 3a-5a, which form complexes with Ag, Cu, and Ni salts. They are also able to adsorb these metals from solutions. The hetero-condensation reaction of silanes 4-8 with OH groups of zeolite (Z), silica gel (S) and glass (G) delivers the modified materials (Z4, S7, G4, G5, G7, G8, etc.), which can adsorb ions of noble metal (Au, Rh, Pd: G4 + Au, G5 + Pd, G7 + Rh). Thus, the synthesized Si-organic polymers and materials turned out to be promising sorbents (enterosorbents) of noble, heavy, toxic metal ions and can be applied in industry, environment, and medicine.

Waterborne Eco-Sustainable Sol-Gel Coatings Based on Phytic Acid Intercalated Graphene Oxide for Corrosion Protection of Metallic Surfaces.

In the past few years, corrosion protection of metal materials has become a global challenge, due to its great economic importance. For this reason, various methods have been developed to inhibit the corrosion process, such as surface treatment approaches, by employing corrosion inhibitors through the deposition of opportunely designed functional coatings, employed to preserve from corrosion damages metallic substrates. Recently, among these techniques and in order to avoid the toxic chromate-based pre-treatment coatings, silane-based coatings and films loaded with organic and inorganic corrosion inhibitors have been widely used in corrosion mitigation water-based surface treatment. In this study, the synthetic approach was devoted to create an embedded, hosted, waterborne, and eco-friendly matrix, obtained by use of the sol–gel technique, through the reaction of functional alkoxysilane cross-linking precursors, namely (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and (3-aminopropyl)triethoxysilane (APTES), in the presence of graphene oxide (GO) intercalated with natural and non-toxic phytic acid (PA) molecules. As a matter of fact, all experimental results from FT-IR spectroscopy, UV–Vis analysis, and SEM confirmed that PA molecules were successfully decorated on GO. Furthermore, polarization measurements and a neutral salt spray test were used to evaluate the anticorrosive performance on aluminum and steel substrates, thus showing that the GO-PA nanofiller improved the barrier and corrosion protection properties of the developed functional silane-based coatings.

Self‐Aligned Polymer Film Patterning on Microstructured Silicon Surfaces

AbstractBased on a recently developed selective etching process for silicon samples with buried implants, this work presents a method for utilizing the generated material contrast between silicon and silicon oxide to selectively deposit polymers on the patterned surface. Besides depositing polystyrene selectively on the etched parts via drop‐casting and dewetting, polymer chains are selectively grafted to the oxidic surface parts. To this end, the oxide surfaces are selectively modified via functional alkoxysilanes, whereas etched silicon surfaces are unreactive. Using either a two‐step or a straight‐forward one‐step process employing commercially available chemicals, atom transfer radical polymerization (ATRP) initiator functions are attached selectively to the non‐etched surface areas, and subsequently used to polymerize either methyl methacrylate (MMA) or N‐isopropyl acrylamide (NIPAM) in a controlled surface‐initiated activator regenerated by electron transfer (ARGET)‐ATRP process. This procedure allows for the further self‐aligned functionalization of the micropatterned samples, enabling the production of highly functional, patterned surfaces, potentially suitable for applications in areas such as cell adsorption, microfluidics, or functional microsystems, e.g., MEMS.

Functional silsesquioxane polymers with branched perfluoroalkyl substituents: Synthesis and prospect applications

Condensation of alkoxysilanes in the active medium, which means acetic or trifluoroacetic acids, is a convenient and versatile method for preparing silsesquioxane copolymers with various functional groups. The method does not require the selection of special conditions, the use of additional solvents and catalysts. The obtained copolymers from poorly compatible monomers are homogeneous in composition without the use of additional solvents. Starting from commercially available functional triethoxisilanes and triethoxysilyl derivatives with branched tert-perfluorohexyl substituents (RF = CF3CF2CF2C(CF3)2(CH2)3-) under condensation in an active medium new functional silsesquioxane polymers with various groups (–NH2, –SH, or –COOH) were obtained. The synthesis techniques used provided a high yield of the resulting copolymers (91–94%). Despite the low compatibility of perfluoroalkyl organosilicon compounds with functional alkoxysilanes, the resulting copolymers are homogeneous in composition, which was confirmed by NMR and GPC. Copolymers are effective modifiers for the surface of materials. In particular, they were used as water repellents for cotton and polyamide fabrics. Modified surfaces of cotton and polyamide fabrics acquired highly hydrophobic properties (α ˃ 120°). The presence of –NH2, –SH or –COOH groups in the chemical structure of fluorinated silsesquioxane copolymers provided high washing-resistant of modified cotton textile. For polyamide fabric, a similar effect was achieved where copolymers with –NH2 or –SH groups were used. The COOH-containing copolymer coating on the polyamide textile do not provide resistance of the modified polyamide textile to repeated washing. Thus, we demonstrated that the new functional silsesquioxane polymers with branched perfluoroalkyl substituents and –NH2 or –SH groups are versatile and efficient hydrophobic agents for both cotton and polyamide textiles.

Siloxane-Silver Nanofluid as Potential Self-Assembling Disinfectant: A Preliminary Study on the Role of Functional Alkoxysilanes

Antimicrobial drug resistance among bacterial and fungal communities have been created a huge challenge for clinicians in treating infections. Conventional antibiotics get non-functional with time due to the rapid adaptation of microorganisms to the environment. Therefore, exploring alternative antimicrobial drugs/nanomaterials to treat such infections is highly needed. Therefore, an alternative to conventional antibiotics, functional alkoxysilane capped Ag-NPs synthesized from 3-aminopropyltrimethoxysilane mediated conversion of silver cations in the presence of three different organic reducing agents, i.e., cyclohexanone, 3-glycidoxypropyltrimethoxysilane and formaldehyde. The antimicrobial potential of synthesized silver nanoparticles was tested against Acinetobacter bauminnii, Candida albicans (mostly causes nosocomial infections) and sporangiospores of Mucorales (Rhizopus arrhizus), which showed a promising result. In addition to low MIC values, these Ag-NPs have shown variable killing dynamics as a function of reducing agents. Further, these functionalized silver nanoparticles were mixed with siloxane polymer to prepare three different siloxane-silver nanofluids. Siloxane-silver nanofluid can be self-assembled when diluted in a desirable volatile solvent on any inanimate surfaces such as medical catheters, surgical clothes and surgical bandages. Finally, the sprays were converted into thin films on sterile plastic strips and examined for their antibacterial activity against drug-resistant bacteria A baumannii. The antibacterial activity of nanofluid thin film has been found as a function of organic reducing reagents that control the morphology of the self-assembled film.

Organotrialkoxysilane-mediated synthesis of Ni–Pd nanocatalysts at lower concentrations of noble metal: Catalysts for faster hydrogen evolution kinetics

The fabrication of alkoxysilane-based nickel (Ni)–palladium (Pd) bimetallic nanoparticle catalysts with several compositions (Pd—0.001M and Ni—0.001–0.1M) was attempted for the first time; these materials were investigated for use as low-cost catalysts in the hydrogen evolution reaction (HER). Functional alkoxysilane [2-(3,4 epoxycyclohexyl)ethyltrimethoxysilane]-assisted conversion of Pd2+ to Pd0 was demonstrated. Palladium nanocrystallites with an average dimension 4.03 ± 1.29 nm were synthesized, which acted as seeds in the synthesis of Ni–Pd bimetallic nanoparticles. The effect of the nanoparticle catalysts on the HER in an alkaline environment was studied using linear sweep voltammetry and electrochemical impedance spectroscopy. A nanostructured thin film containing Ni3PdNPs produced a 100 mA cm−2 current density at an overpotential of −90 mV with a small Tafel slope of 25 mV dec−1 at a catalyst loading of 0.1 mg cm−2. The annealed Ni3PdNPs catalyst further enhanced the current density to ∼ 240 mA cm−2 at an overpotential of −56 mV.

Organotrialkoxysilane mediated rapid and controlled synthesis metal nanoparticles in both homogeneous and heterogeneous phase and their catalytic applications

Organotrialkoxysilanesilane (e.g., 3-glycidoxypropyltrimethoxysilane-3-GPTMS, 3-aminopropyl trimethoxysilane-3-APTMS) mediated synthesis of noble metal nanoparticles (AuNPs, AgNPs) and their multimetallic analogues (Au–Ag bimetallic and Au–Ag–Pd trimetallic nanoparticles) over short durations (5–120 s) is reported. These functional alkoxysilanes are microwave active, allowing a significant reduction in time for nanoparticle synthesis with high stability for practical applications. The process also enables incorporation of noble metal nanoparticles within silica nanoparticles. Examples of AuNP, PdNPs, and Pd–Ni bimetallic within mesoporous silica nanoparticles are reported. The catalytic activity of these nanoparticles and their multimetallic analogues for organic dye degradation was evaluated. Synergistic interactions in bimetallic and trimetallic nanoparticles promote rapid degradation of methylene blue. A comparison of the catalytic activity of monometallic noble metal nanoparticles and their multimetallic analogues on methylene blue degradation is reported herein.

Solid‐state ion sensor for on‐chip determination of potassium ion in body fluid

AbstractThis article describes a synthetic route for the fabrication of all‐solid‐state potentiometric ion‐sensing device for on‐chip determination of potassium ion in body fluid. The sensing electrodes comprised of (a) a solid‐state reference electrode made from a Ag/AgCl‐printed electrode covered with a solid‐electrolyte‐embedded membrane made from siloxane polymer and (b) solid‐state ion‐selective electrode as working electrode made by assembling ionophore‐impregnated PVC membrane casting solution over a ion exchanger‐impregnated membrane. The ion exchanger‐impregnated membrane is cast by assembling siloxane–polyindole nanodispersion over working electrode of screen‐printed electrode to yield constant dipolar potential. The screen‐printed electrodes comprising of all‐solid‐state reference and working electrode can be operated under zero current flow to monitor potassium ion in given sample. The configuration of the printed electrodes is designed to fix a microneedle assembly over the working portion of both reference and working electrodes for transdermal ion sensing. The functional alkoxysilanes derived from nanodispersion allow to make solid‐state reference electrode avoiding the use of internal filling solution providing innovation in designing potentiometric sensor. In one aspect, a potentiometric device for detecting analyte in biological fluid that can include a array of hollowed microneedle in which each needle acts as protruded needle structure including an exterior wall forming a hollow interior covering both solid‐state working and reference electrode with an opening at terminal end in such that one microneedle is converted into a potassium ion‐selective electrode.

Aerosol-assisted chemical vapour deposition of transparent superhydrophobic film by using mixed functional alkoxysilanes

A method for the preparation of transparent superhydrophobic silica coatings on glass substrates via aerosol‐assisted chemical vapour deposition (AACVD) is described. A multi-layer process to produce dual scale silica nanoparticles films, by using different functional alkoxysilanes was investigated. A first layer of 3-methacryloxypropyltrimethoxysilane (MPS) and a second layer of tetraethylorthosilicate (TEOS) were deposited at different temperatures to generate micro and nano particles of silica. Finally, a layer of perfluorooctyltriethoxysilane was deposited on top of the two layers to achieve superhydrophobicity. The transparent superhydrophobic film showed transparency of 90% in the visible light region with a static water contact angle of 165° and a sliding angle lower than 1°. Various durability tests were performed on the transparent superhydrophobic film, showing a constant water repellency after corrosion and organic solvents tests, strong resistance under UV light, and thermal stability up to 400 °C. Sandpaper mechanical robustness durability test showed superhydrophobicity for up to 5 rubbing cycles. In this study, a novel strategy to achieve highly transparent superhydrophobic glass surfaces using AACVD of alkoxysilanes, to produce surfaces with excellent durability is described. This shows great potential to obtain silica superhydrophobic films for large–scale applications.

Amine-modified mesoporous silicas: Morphology-controlled synthesis toward efficient removal of pharmaceuticals

Abstract To investigate the effect of porous structure and surface chemistry on the efficiency of pharmaceuticals removal four different types of pristine and amine-modified mesoporous silicas have been synthesized and characterized: Ordered Mesoporous Silicas (SBA-15), Mesocellular Silica Foams (MCF), Porous Silica Nanotubes (PSN) and Amorphous Silica Xerogels (ASX). Functional alkoxysilanes bearing one, two and three amine groups were co-condensed with tetraethoxysilane to obtain highly functionalized materials. The designed materials were tested as sorbents of several drugs commonly considered priority hazardous pharmaceuticals, including diclofenac, ibuprofen, penicillin G and naproxen. The porous structure turned out to have a minor effect on the sorption capacity but the number of surface amine groups was the crucial parameter. Unprecedented uptakes of drugs sometimes exceeding 0.9 g g−1 testify that the obtained materials can be applied for removal of drugs from water and wastewaters, particularly when high concentrations of pharmaceutical are needed to be removed.

Preparation and characterization of stable DQ silicone polymer sols

Stable DQ silicone polymer sols composed of di (D)- and tetra (Q)-functional alkoxysilanes were prepared by the following methods: (i) co-hydrolysis–condensation between diethoxy(dimethyl)silane (DEDMS) and tetraethoxysilane (TEOS) (DEDMS–TEOS as random copolymer sols), (ii) co-hydrolysis–condensation between poly(dimethylsiloxane) (PDMS) and TEOS (PDMS–TEOS as random block copolymer sol), and (iii) triethoxysilylation of a PDMS-lithium salt (PDMS–TES). The polymer sols were characterized by GPC, NMR, and FT-IR. The differences in properties between the structures were analyzed from their thermal stabilities and by using the swelling test. Thermal stabilities of these polymer sols were increased with the increase in the chain length of the D domain and with decrease in hydrolyzability. The swelling of films via polymer sols was decreased with the increase in the degree of crosslinking in sols.

Synthesis of new organoelement copolymers based on polydimethylsiloxanes and aminophosphonates

Based on commercially available 3-Aminopropyl (diethoxy)methylsilane new alkoxysilane with functional aminophosphonate group - diethyl (2-((3-(diethoxy (methyl)silyl)propyl)amino)propan-2-yl)phosphonate were synthesized and characterized. Obtained functional alkoxysilane were transformed to tetrasiloxane in active medium in the presence of acetic acid and then copolymerized with octamethylcyclotetrasiloxane (D4). The chemical structure of the resulting polymer was studied and confirmed by a combination of physical methods, namely, 1H, 13C, 31P and 29Si NMR, GPC, and IR spectroscopy. The thermophysical and rheological properties of the polymer were also studied.

Functional alkoxysilane mediated controlled synthesis of Prussian blue nanoparticles, enabling silica alginate bead development; nanomaterial for selective electrochemical sensing

We report herein the controlled synthetic strategy for Prussian blue nanoparticles (PBNPs) formation justifying the role of functional alkoxysilanes, [2-(3,4-Epoxycyclohexyl)ethyl]trimethoxysilane (EETMSi) in the presence of tetrahydrofuran hydroperoxide (THF-HPO) with following major findings: (i) significant change in nanogeometry from 40 to 8 nm by addition of EETMSi and (ii) allowed fabrication of PBNPs encapsulated silica-alginate beads. As made nanoparticles were characterized by UV–Vis spectroscopy, TEM, FT-IR, and SEM. Size dependent electrochemical behavior of three different PBNPs i.e. PBNPs-1 (26 nm), PBNPs-2 (17 nm) and PBNPs-3 (8 nm) was recorded based on cyclic voltammetry. Apart from unprecedented size-dependent properties, as made PBNPs-3 display excellent peroxidase mimetic activity with Km value to the order of ∼0.9 mM. In addition, EETMSi also allows to cast Prussian blue film and simultaneously enable the formation of silica-alginate beads with controlled pores size perfectly suitable for encapsulating these nanoparticles which allocate selective electrochemical oxidation of Pyrogallol (Py) at 0.3 V vs. Ag/AgCl.

Preparation and Characterization of Functional Alkoxysilanes via Catalyst‐Free Aza‐Michael Reaction

AbstractIt is challenging to functionalize alkoxysilanes since they are moisture sensitive. The aza‐Michael reaction is reported as a simple and efficient way to prepare functional alkoxysilanes. The alkoxysilanes were synthesized by reacting amino‐alkoxysilanes with electron‐deficient alkenes under mild reaction conditions without any catalyst. The yield was very high, and a wide range of functional groups could be tolerated in this methodology to form monofunctional or multifunctional alkoxysilanes.

Novel concept for the preparation of gas selective nanocomposite membranes

In this work we report on a novel concept for the preparation of gas selective composite membranes by a simple and robust synthesis protocol involving a controlled in-situpolycondensation of functional alkoxysilanes within the pores of a mesoporous ceramic matrix. This innovative approach targets the manufacture of thin nanocomposite membranes, allowing good compromise between permeability, selectivity and thermomechanical strength. Compared to simple infiltration, the synthesis protocol allows a controlled formation of gas separation membranes from size-adjusted functional alkoxysilanes by a chemical reaction within the mesopores of a ceramic support, without any formation of a thick and continuous layer on the support top-surface. Membrane permeability can thus be effectively controlled by the thickness and pore size of the mesoporous layer, and by the oligomers chain length. The as-prepared composite membranes are expected to possess a good mechanical and thermomechanical resistance and exhibit a thermally activated transport of He and H2 up to 150 °C, resulting in enhanced separation factors for specific gas mixtures e.g. FH2/CO ∼ 10; FH2/CO2 ∼ 3; FH2/CH4 ∼ 62.

Polymer Surface Engineering for Efficient Printing of Highly Conductive Metal Nanoparticle Inks.

An approach to polymer surface modification using self-assembled layers (SALs) of functional alkoxysilanes has been developed in order to improve the printability of silver nanoparticle inks and enhance adhesion between the metal conducting layer and the flexible polymer substrate. The SALs have been fully characterized by AFM, XPS, and WCA, and the resulting printability, adhesion, and electrical conductivity of the screen-printed metal contacts have been estimated by cross-cut tape test and 4-point probe measurements. It was shown that (3-mercaptopropyl)trimethoxysilane SALs enable significant adhesion improvements for both aqueous- and organic-based silver inks, approaching nearly 100% for PEN and PDMS substrates while exhibiting relatively low sheet resistance up to 0.1 Ω/sq. It was demonstrated that SALs containing functional -SH or -NH2 end groups offer the opportunity to increase the affinity of the polymer substrates to silver inks and thus to achieve efficient patterning of highly conductive structures on flexible and stretchable substrates.

Functionalized alkoxysilane mediated controlled synthesis of noble metal nanoparticles dispersible in aqueous and non-aqueous medium.

The synthesis of amphiphilic noble metal nanoparticles involving the functional role of 3-aminopropyltrimethoxysilane (3-APTMS) and 3-glycidoxypropyltrimethoxy-silane (3-GPTMS) is reported herein. The mechanistic approach on the reactivity of these functional alkoxysilane for the typical controlled synthesis of AuNPs as evidenced from UV-visible spectroscopy and transmission electron microscopy (TEM) is reported. The experimental findings demonstrate the followings; (1) Methanolic solution of 3-GPTMS undergo interaction with 3-APTMS and the same is facilitated in the presence of 3-APTMS treated noble metal ions, (2) The molar ratio of 3-GPTMS/3-APTMS control the nanogeometry as well as the dispersibility of AuNPs in both aqueous and non-aqueous media, (3) the dispersion ability of nanoparticles is found to be based on the hydrophobic alkyl chain of the reaction product of 3-GPTMS and 3-APTMS, and (4) AuNPs shows absorption maxima as a function of polarity and refractive index of the medium. A typical application of as synthesized AuNPs as peroxidase mimetic is reported.

Preparation of composite‐imprinted alumina membrane for effective separation of p‐hydroxybenzonic acid from its isomer using Box–Behnken design–based statistical modeling

ABSTRACTHighly selective composite imprinted membrane for p‐hydroxybenzonic acid (p‐HB) was prepared by using semicovalent imprinting technique. A thermally reversible covalent bond was used to link p‐HB molecule to a functional alkoxysilane monomer to generate covalently bound imprint precursor. This precursor was incorporated into a cross‐linked functional silica sol with the tetraethoxysilane as cross‐linker via a typical acid‐catalyzed, sol‐gel synthesis. Then, the SCIM was prepared through dipping and grafting on the upper side and inner pores of the Al2O3 microporous membrane and then removing of the template molecule after thermal treatment. Compared with composite imprinted membrane via noncovalent imprinting approach as well as the black Al2O3 microporous membrane, the SCIM exhibited higher membrane flux and selective rebinding of p‐HB as well as showing excellent permeability for p‐HB. Response surface methodology was used to investigate the best combination of separation conditions in the dynamic separation process. The optimal conditions for the separation of p‐HB from salicylic acid were as follows: the p‐HB concentration of 5 mg L−1, the temperature of 10°C, and the flow rate of 1 mL min−1. Under these conditions, the experimental selective separation factor was 32.75 ± 0.91%, which was close to the predicted selectivity coefficient value. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40621.

Silica nanocapsules for redox-responsive delivery

Redox-responsive silica nanocapsules with a hydrophobic liquid core were synthesized by reactive templating of miniemulsion droplets with functional alkoxysilanes. Tetrasulfide bridges were successfully introduced into the inorganic shell and were found to be accessible for chemical reactions as shown by 31P-NMR spectroscopy. Indeed, the tetrasulfide groups could be reduced to yield thiol groups. A subsequent increase of permeability of the silica shell was observed upon reduction of the tetrasulfide groups.