Isocyanatopropyltriethoxysilane Research Articles

Enhancement of ammonia corrosion resistance of coatings through improving dispersion and binding site of graphene oxide in silane coatings

Copper metal is essential to our production process, but it is highly corrosive in an ammonia environment and must be highly valued. Anti-corrosion coating is a simple and cost-effective method of preventing metal corrosion. In this study, a composite silane coating was prepared on copper using an impregnation method with mercaptopropyltriethoxysilane (TPTES) as the silane substrate and graphene oxide (GO) modified with isophorone diisocyanate (IPDI) or isocyanatopropyltriethoxysilane (IPTS) as filler to protect the copper from ammonia corrosion. The coating samples were hanging tested against ammonia corrosion by setting up two corrosive environments: ammonia gas and ammonia water. After 20 days of corrosion, the surfaces of the TPTES/IPDI-GO and TPTES/IPTS-GO coatings remained unchanged under both ammonia environments and the corrosion rate was consistently low at 2–3 μm/y. Additionally, the coating exhibited high protective qualities according to the electrochemical impedance spectroscopy (EIS) test in a 3.5% NaCl solution, which is attributed to the good dispersion that improves the densification and regularity of the coating. Meanwhile, IPTS-GO has a greater binding force with the coating matrix due to the increased number of reactive sites, resulting in further improved corrosion protection. This study provides an idea for research on ammonia-resistant coatings.

Architecture of Nanoantioxidant Based on Mesoporous Organosilica Trp-Met-PMO with Dipeptide Skeleton.

A nanoantioxidant of mesoporous organosilica (Trp-Met-PMO) based on the framework of tryptophan-methionine dipeptide was first designed and constructed by condensation between self-created dipeptide organosilica precursor (Trp-Met-Si) and tetraethyl orthosilicate (TEOS) in alkaline conditions under the template hexadecyl trimethyl ammonium bromide (CTAB). Trp-Met-Si was prepared by the reaction between dipeptide Trp-Met and conventional organosilicon coupling agent isocyanatopropyltriethoxysilane (IPTES) via a multiple-step reaction method. The material Trp-Met-PMO was confirmed by XRD, FT-IR and N2 adsorption-desorption analysis. The material Trp-Met-5-PMO with low amounts of organosilica precursor remained a mesoporous material with well-ordered 2D hexagonal (P6mm) structure. With increasing amounts of organosilica precursor, a mesoporous structure was still formed, as shown in the material Trp-Met-100-PMO with the highest amounts of organosilica precursor. Moreover, pore size distribution, surface area and porosity of Trp-Met-PMO are regulated with different amounts of organosilica precursor Trp-Met-Si. The antioxidant activity of Trp-Met-PMO was evaluated by ABTS free radical-scavenging assay. The results showed that antioxidant activity was largely enhanced with increasing contents of organosilica precusor Trp-Met-Si in the skeleton. The material Trp-Met-40-PMO exhibited maximum scavenging capacity of ABTS free radicals, the inhibition percent was 5.88%. This study provides a design strategy for nanoantioxidant by immobilizing short peptides within the porous framework of mesoporous material.

Synergistic enhancement of UV-resistance and electrical conductivity of waterborne polyurethane composite with combination of functionalized 2D graphene oxide and 1D nanocellulose

In this work, a functionalized graphene oxide@functionalized nanocellulose (FGO@FNC) composite filler, that was firstly synthesized by using isocyanatopropyltriethoxysilane (IPTS) as a coupling agent through a sol-gel process, and subsequently incorporated into waterborne polyurethane (WPU) dispersion via a simple and scalable solution blending method to prepare WPU composite (WPU/FGO@FNC). It was found that for the as-prepared FGO@FNC filler, the urethane chains were covalently grafted onto the surface of 2D graphene oxide and 1D nanocellulose, as well as siloxane linkages were formed between FGO and FNC as a result of co-condensation. Notably, the inserted FGO@FNC filler, dispersing excellently within the WPU matrix, could reinforce mechanical properties, improve surface hydrophobicity and electrical conductivity of WPU/FGO@FNCs composites, and particularly enhance the UV-resistant performance. Furthermore, the most effective enhancement was acquired when 3 wt% of FGO@FNC was incorporated into the WPU matrix, i.e., the WPU/FGO@FNC3 composite, that showed surpassing mechanical properties (σb = 28.7 MPa, εb = 462.8 %), water contact angle (96.5°), and electrical conductivity (0.252 S/m); and more importantly, it retained considerably in physicochemical parameters nearly above 78 % after five days of UV exposure. This work offers a viable avenue for developing UV-resistant, electrical conductive, tough and hydrophobic multi-functional coatings.

Obtención de materiales híbridos homogéneos de tipo Orgánico/Inorgánico

Tridimensional polymers are mutually incompatible and a solution is the formation of interpenetrating polymer networks (IPN’s). In order to obtain optically transparent plaques, the polyurethane (PU), polymethylmetacrylate (PMMA) and sílica (SiO2) were syntetized and we obtained the best conditions of reaction for each material. We sintetized the binary networks and the ternary ones with different percentage from sílica were obtained, incorporating to the system 10% in weight of sílica, carrying out a curing in situ in mass. The interest of this work lies in the association of an inorganic network (SiO2) to two organic networks PU and PMMA. In order to reduce the phase separation that occurs in the PU, PMMA and SiO2 system, coupling agents of organic/inorganic nature were introduced. Optically transparent plaques were obtained using trimethoxysilyl propyl methacrylate and isocyanatopropyl triethoxy silane. The materials were characterized by Fourier Transformed Infrared Spectroscopy, verifying the presence of representative functional groups in each of the samples. The purpose of incorporating these materials to a single network is the improvement of the mechanical, optical and thermal properties of the organic polymers.

Development of an Electrochemical Sensor Based on Covalent Molecular Imprinting for Selective Determination of Bisphenol‐A

AbstractIn this study, an electrochemical sensor was developed and used for selective determination of bisfenol‐A (BPA) by integrating sol‐gel technique and multi‐walled carbon nanotubes (MWCNTs) modified paste electrode. BPA bounded by covalently to isocyanatopropyl‐triethoxy silane (ICPTS) was synthesized as a new precursor (BPA‐ICPTS) and then BPA‐imprinted polymer (BPA‐IP) sol‐gel was prepared by using tetramethoxysilane (TMOS) and BPA‐ICPTS. Non‐imprinted polymer (NIP) sol‐gel was obtained by using TMOS and (3‐Aminopropyl) triethoxysilane. Both BPA‐IP and NIP sol‐gels were characterized by nitrogen adsorption‐desorption analysis, FTIR, SEM, particle size analyzer and optical microscope. Carbon paste sensor electrode was fabricated by mixing the newly synthesized BPA‐IP with MWCNTs, graphite powder and paraffin oil. The electrochemical characterization of the sensor electrode was achieved with cyclic and differential pulse voltammetric techniques. The response of the developed sensor under the most proper conditions was linear in BPA concentration range from 4.0×10−9 to 1.0×10−7 mol L−1 and 5.0×10−7 to 5.0×10−5 mol L−1 and the detection limit was 4.4×10−9 mol L−1. The results unclosed that the proposed sensor displayed high sensitivity and selectivity, superior electrochemical performance and rapid response to BPA.

Effect of nano‐TiO2 surface modification on polarization characteristics and corona aging performance of polyimide nano‐composites

ABSTRACTUsing coupling agent isocyanatopropyltriethoxysilane (ICTOS) to modified nano‐TiO2, the polyimide (PI) with different titanium dioxide (TiO2) contents (0, 1, 2, 3, 4, and 5 wt %) doped nano‐composites were prepared by sol–gel method (PI/TiO2 ICTOS composites). The effect of ICTOS modification on polarization and time‐to‐breakdown properties of composites were investigated by thermally stimulated depolarization current (TSDC) method, dielectric, and Corona aging measurements. The TSDC spectra show that ICTOS modification enhanced α‐peak intensity and make β‐peak disappear in composites. Relevant trap parameters were calculated by an approximate model, and the results indicate that introduction of ICTOS is effective for the charge carrier traps, activation energy distribution in composites. Corona aging measurement show corona resistance was also sufficient improved in PI/TiO2 ICTOS composites. The changes of activation energy and intensity of traps in composites may be responsible for the corona resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45101.

Synthesis of SiO2/epoxy–benzoxazine ternary copolymer via sol–gel method: Thermal and mechanical behavior

Trialkoxy–terminated benzoxazine monomer was synthesized using bisphenol A (BPA), 3–aminopropyltriethoxysilane (KH–550) and paraformaldehyde. Subsequently, bisphenol F epoxy resin (F51) was pretreated with 3–isocyanatopropyltriethoxysilane (IPTS) to covalently introduce trialkoxy group into the epoxy molecular. Sol–gel process was then initiated with tetraethoxysilane (TEOS) as precursor to introduce silica structure into epoxy–benzoxazine hybrid before curing reaction. The synthesized benzoxazine and epoxy resin containing trialkoxysilane group were used as silane coupling agent to connect epoxy–benzoxazine matrix as organic domain and silica units as inorganic domain. Thermal gravimetric analysis (TGA) and dynamic mechanical analysis (DMA) show that the organic–inorganic ternary copolymer possesses promoted thermal stability compared with the unmodified epoxy–benzoxazine matrix. The char residues of the ternary copolymer after decomposition test reveal a dense surface layer and unbroken original dimension which is in accordance with the TGA results. According to the results of the mechanical tests and DMA, the SiO2/epoxy–benzoxazine copolymer possesses improved toughness and is more capable of absorbing deformation energy under external force.

Development of polybenzoxazine–silica–titania (PBZ–SiO2–TiO2) hybrid nanomaterials with high surface free energy

In the present work, silica and titania reinforced polybenzoxazine (PBZ–SiO2–TiO2) hybrid nanomaterial possessing high surface free energy have been developed using dimethylol-functional benzoxazine monomer (4HBA-BZ), tetraethoxysilane (TEOS), 3-(isocyanatopropyl)triethoxysilane (ICPTS), titaniumisopropoxide (TIPO) through an in situ sol–gel process. Data obtained from the contact angle measurement indicate that the hybrid materials are hydrophilic in nature and possess a high surface free energy. For example, hybrid PBZ obtained from 1:1:0.6:0.4 (m:m:w:w) ratio of 4HBA-BZ:ICPTS:TEOS:TIPO (PBST4) exhibit a high surface free energy of 38.2 mJm−2 which is higher than that of neat polybenzoxazine (29.5 mJm−2). Further data resulted from thermal studies indicate that the hybrid PBZ possess higher values of Tg, thermal stability and char yield than those of neat PBZ.

Preparation and Study on the Electric Properties of PI-Al<sub>2</sub>O<sub>3</sub> /PI-TiO<sub>2</sub>/PI-Al<sub>2</sub>O<sub>3 </sub>Three Layers Nanocomposite Films

Polyimide-Al2O3 nanocomposite films were prepared via simple mechanical blending of Polyimide and surface modified Al2O3, and Polyimide-TiO2 nanocomposite films were prepared by the polymerization process of adding tetrabutyl orthotitanate (TBOT) and the coupling agent isocyanatopropyltriethoxysilane (ICTOS) in polyimide. The three layers nanocomposite films were characterized by scanning electron microscope (SEM). The homogeneous dispersion is observed by the SEM when the concentration of Al2O3 is low. The electrical properties of the nanocomposite films were investigated as a function of the concentration of the Al2O3 nanoparticles. The results show that the dielectric constant and the dielectric loss (tan δ) of these films increased with the increase of the content of silica particles.

Investigation on the Morphology and Dielectric Properties of PI/SiO<sub>2</sub> Nanocomposite Films

Polyimide nanocomposite insulating materials are widely used in electrical and electron engineering owing to their outstanding electrical, mechanical, thermal, and wear-resistance properties. Polyimide/silica (PI/SiO2) nanocomposites have been prepared by the polymerization process of adding tetraethoxysilane (TEOS) and the coupling agent isocyanatopropyltriethoxysilane (ICTOS) in polyimide. The effects of SiO2addition on the microstructure and the dielectric property of nanocomposite films were investigated. It was found that the silica particles were well dispersed in PI matrix and the sizes of SiO2particles in the hybrid films range from 20 nm to 30 nm for 5-15 wt% SiO2loading in the matrix. The dielectric constant and the dielectric loss (tan δ) of these films increased with the increase of the content of silica particles.

Structure and mechanical properties of the hybrid films of well dispersed SiO2 nanoparticle in polyimide (PI/SiO2) prepared by sol–gel process

The hybrid films of well dispersed SiO2 nanoparticle in polyimide (PI/SiO2) were prepared through the sol–gel processing. The pure PI was synthesized from 4, 4′,-oxydianaline (ODA) and pyromellitic dianhydride (PMDA). The residual amino groups which were controlled by the reactant stoichiometric ratio reacted with the coupling agent isocyanatopropyltriethoxysilane (ICTOS) to provide an organic–inorganic bonding. A series amount of tetraethoxysilane (TEOS) was then added, thus producing chemically bonded composite films. The films with different silica contents (0 wt %, 5 wt %, 8 wt %, 10 wt %, 13 wt %, and 15 wt %) were characterized by a variety of techniques including FT-IR, SEM, TGA, and tensile analysis. The results indicated that the chemical interaction between the two phases resulted in the formation of well-dispersed nanoparticles (20–30 nm) in the PI matrix, and superior thermal stability of hybrid films. The tensile measurement showed that the mechanical properties were markedly improved with incorporating various amount of silica, and the maximum of tensile strength was 105.4 MPa with10 wt % of silica concentration.

Fabrication of thermo-responsive nano-valve by grafting-to in melt of poly(N-isopropylacrylamide) onto nanoporous silicon nitride membranes

This article reports the grafting-to in melt of amino and carboxy-terminated poly(N-isopropylacrylamide) (PNIPAM) onto ultrathin nanoporous silicon nitride membranes (NSiNMs) with a mean pore size of 85±15nm functionalized respectively with a self-assembled monolayer (SAM) of isocyanatopropyltriethoxysilane (ICPES) and glycidylpropyloxytrimethoxysilane (GPS) to achieve permeation control and obtain thermo-responsive nano-valves. The presence of PNIPAM onto the surface was controlled via X-ray photoelectron spectroscopy (XPS) analysis and the grafting characteristics such as the grafting density and the distance between grafting sites were calculated from the ellipsometric measurements of the dry PNIPAM films. The modified NSiNMs were then integrated into a diffusion cell and used for vitamin B12 and fluorescein isothiocyanate-dextrans (FITC-dextrans) diffusion experiments to demonstrate the reversible and reproducible thermo-responsive behavior of the whole device. By controlling the temperature of the system below and above the lower critical solution temperature (LCST) of the PNIPAM (32°C), the nanopores can switch from a closed state (swollen state of the chains below the LCST) to an opened state (collapsed state of the chains above the LCST). The clear ON-OFF behavior of the grafted NSiNMs has been observed for the diffusion of FITC-dextran molecules with a hydrodynamic radius superior to 3nm.

The cause of absorption and luminescence band shift of disperse Red-13 in silica spheres

Optical absorption and luminescence band shifts have been observed for a disperse red-13 (DR-13) attached on silica spheres. A covalent bond is formed between an isocyanatopropyl triethoxysilane (ICPTES) and a DR-13 prior to DR-13 being incorporated inside the spheres. The Stober synthesis process was performed with the synthesized ICPTES-DR-13 (ICPDR), tetraethoxy orthosilane (TEOS), 2-propanol and NH4OH solution. The final silica spheres with ICPDR (ICPDRSS) were analyzed with Fourier transform infrared, UV-visible and fluorescence spectrometers. Characteristic absorption peaks at 1700 and 1704 cm−1 representing −C=O stretching vibrations for ICPDR and ICPDRSS indicate the formation of urethane linkages. Although the absorption band at 502 nm did not shift with increasing concentration of DR-13 in methanol, the absorption band for the ICPDRSS shifted 28 nm toward shorter wavelength due to the antiparallel geometry of the azochromophores. A broad luminescence was observed for ICPDRSS and shifted toward the blue with increasing excitation wavelength, which was due to a transformation of the DR-13 in silica spheres from a trans-form to a cis-form.

In situ sol–gel synthesis of silica reinforced polybenzoxazine hybrid materials with low surface free energy

In the present work, silica reinforced polybenzoxazine (PBZ–SiO2) hybrid materials possessing low surface free energy have been developed using a dimethylol-functional benzoxazine monomer (4HBA-BZ), tetraethoxysilane (TEOS) and 3-(isocyanatopropyl)triethoxysilane (ICPTS) through an in situ sol–gel process. Data from the contact angle measurement indicate that the hybrid materials are hydrophobic in nature and possess a low surface free energy. For example, a PBS3 hybrid material (1 : 1 : 1 ratio of 4HBA-BZ : ICPTS : TEOS) exhibits a low surface free energy of 18.6 mJ m−2 which is lower than that of poly(tetrafluoroethylene) (22.0 mJ m−2). Further data obtained from thermal studies indicate that the hybrid PBZ possesses higher values of the glass transition temperature (Tg), thermal stability and char yield than those of neat PBZ.

Preparation and characterization of transparent polyarylethers-silica hybrid membranes with covalently connected phases

From the molecular designing point of view, (p-amino)phenylhydroquinone (APH) and (3, 5-dimethoxy)phenylhydroquinone (DMPH) were prepared in a two-step synthesis. Polyetheretherketone with a large number of amino groups (APEEK) and polyethersulfone with quantities of hydroxyl side groups (HPES) were successfully synthesized from these bisphenol monomers. The functionalized polyarylethers were then grafted by isocyanatopropyltriethoxysilane (IPTS) through in-situ O-acylation reaction to obtained triethoxysilyl groups. Subsequently, these hydrolyzed triethoxysilyl groups formed network and produced covalent bonds between organic and inorganic phases via a sol–gel process under acid condition. Transparent polyarylether-silica (PAE-silica) hybrid films were fabricated through this in-situ sol–gel process. Furthermore, tetraethylorthosilicate (TEOS) and SiO2 nanoparticles were introduced as silica sources to improve the content of silica. The in-situ generated SiO2 by hydrolysis of the silica sources with triethoxysilyl groups on IPTS modified polyarylethers was covalently connected with the substrates. The present method achieved transparent hybrid films at high silica content of 40 wt%, which was resulted from inorganic and organic phases closely combination and homogenous distribution of silica particles in the polymer matrix.

Chemical modification of Nitzschia panduriformis's frustules for protein and viral nanoparticle adsorption

The frustule of diatoms, through appropriate chemical modification, can be developed for a high adsorption level of recombinant proteins and viral nanoparticles. Field emission scanning electron microscopy (FE-SEM) analysis of clean frustules revealed a 3D loculate areolae structure (valvar phase porous pattern of the siliceous cell wall). Isocyanatopropyl triethoxysilane (IPS) and iminodiacetic acid (IDA) were used to immobilize Cu2+ ions (an average Cu2+ adsorption capacity about 190μmol of Cu2+/ml of the Cu2+-coupled biosilica reached). FE-SEM, energy dispersion X-ray spectroscopy (EDS) and Fourier transform infrared (FT-IR) were used to confirm the chemical modification of the Cu2+-coupled biosilica. Protein adsorption was confirmed with the detection of a recombinant (His)6-tagged green fluorescent protein binding using fluorescent microscopy. Infectious bursal disease virus VP2-441 subviral particles (SVPs) were found to bind to the Cu2+-coupled biosilica (approximately 3×10−9mol of VP2-441 SVPs/ml of modified frustules), a level higher than the previously obtained 9×10−10mol/ml for SVP binding using a commercial Ni–NTA resin. These give diatom frustules the potential to be developed into a material useful in viral nanoparticle purification systems or as a biosensor for the detection of viruses.

Improvement in Weatherability of Transparent Plastics by Sol-Gel Coating with UV Absorber and HALS

Almost UV-protective coating films have been prepared by simple addition of UV absorber (UVA) into the sol-gel network, which results in the blooming of UVA and lowers mechanical properties of films. In this study, to prohibit the blooming of UVA, we introduced siloxane bonds between modified benzophenone (MBP) obtained from the urethane reaction of 2, 2, 4, 4-tetrahydroxy benzophenone (THBP) with isocyanato propyl triethoxy silane and silane precursors into sol-gel network by hydrolysis and condensation reaction. Also, to improve UV absorption ability, we introduced hindered amine light stabilizers (HALS) as radical scavenger. Silica-gel coating films were prepared by methyl triethoxy silane (MTES), colloidal silica, and UV stabilizers. They were deposited on polycarbonate (PC) substrates by the sol-gel method for preventing their photodegradation. The combination of two different UV stabilizers improved UV stabilization ability. The UVA lifetime was related to not only the quantity of HALS but also the degree of chemical bonding and compatibility between sol-gel network and UV stabilizers.

Preparation and characterization of poly(phthalazinone ether ketone)/SiO2 hybrid composite thin films with low friction coefficient

Organic–inorganic poly(phthalazinone ether ketone) (PPEK)/SiO2 hybrid composite thin films were prepared by the dip-coating method on pre-cleaned glass substrates. The covalent bonds between organic and inorganic phases were introduced by an in-situ O-acylation reaction of isocyanatopropyltriethoxysilane (ICPTES) with the borohydride-reduced PPEK forming a polymer bearing triethoxysilyl groups. Theses groups were subsequently hydrolyzed with tetraethoxysilane (TEOS) and allowed to form a network via a sol–gel process. The polymer hybrid composite exhibited good thermal stability and a higher glass transition temperature as compared with the pure resin. Atomic force microscope, water contact angle measurement and scanning electron microscope were used to characterize the polymer hybrid thin films. The tribological experiment showed that the films have very low friction coefficient (about 0.1) and good anti-wear properties, without failure even after sliding for 18,000 s under modest loads. The improved tribological properties of the modified substrate were attributed to good adherence of PPEK/SiO2 hybrid films on the substrate and synergy of both PPEK matrix and silica particles.

Inter-Phase Bonding in Poly(hyroxyamide)-silica Hybrids: Effect of Isocyanto‐propyltriethoxysilane Addition on the Structure and Properties

Novel aramid‐silica ceramers with increased inter‐phase bonding have been prepared via the sol‐gel process. The aramid chains with pendant alkoxy groups were synthesized by reacting poly(hyroxyaramid) chains with isocyanato‐propyltriethoxysilane (ICTOS). The sol‐gel process was carried out in this matrix after mixing an appropriate amount of tetraethoxysilane (TEOS) to produce a silica network structure chemically bonded to the matrix. The effect of ICTOS addition on morphology, thermal and mechanical properties of the composites has been studied. Properties of the composites were compared with the hybrid system where a similar matrix was used but the silica network was developed using a mixture of ICTOS and TEOS or TEOS alone. The hybrid materials in which ICTOS was added prior to TEOS in the matrix showed better mechanical and thermal properties as compared to the system in which ICTOS and TEOS were used together or where only TEOS was used in the pure aramid matrix. The glass transition temperature was found to increase and the coefficient of thermal expansion was considerably reduced in chemically bonded ceramers as compared to those having no interfacial bonding.

Monitoring morphology and properties of hybrid organic- inorganic materials from in situ polymerization of tetraethoxysilane in polyimide polymer: 1. Effect of the coupling agent on the microstructure and interfacial interaction

Transmission electron microscopy (TEM), small angle X-ray (SAXS) and dynamical mechanical thermal analysis (DMTA) were used to characterize the morphology and thermo-mechanical properties of hybrid organic inorganic materials. These materials were based on polyimide (PI) and tetraethoxysilane (TEOS). Polyimide polymer is prepared from 4,4'-oxydianiline (ODA) 2,2-Bis(3- amino-4-hydroxyphenyl) hexafluoro-propane (6F-OHDA) pyromellitic dianhydride (PMDA) polyamic polymer. In one family of hybrid materials 3- isocyanatopropyltriethoxysilane (ICTS) is used as coupling agent in order to enhance the interfacial interaction between polyimide and silica. It was possible to modulate the morphology as well as the optical and thermo-mechanical properties of these hybrid materials depending on the formulation used. TEM and SAXS analysis indicated that silica domains on the nanoscale level are obtained when coupling agent is used in the formulation. Additionally the TEM and SAXS analysis indicated that miscibility of the organic and the inorganic phases on the molecular scale is obtained in the hybrid films when ICTS as coupling agent is added to the polyamic acid. These techniques show a fractal structure of the hybrid materials with coupling agent. This was confirmed with DMTA analysis which shows very high temperature relaxation (more than 450°C). From this result it could be derived that the addition of ICTS causes a morphological transformation from discrete particulate microstructure to fine interpenetrated or co-continuous phases. The intimate miscibility of the phases is accompanied at the same time by the amelioration of thermo-mechanical properties of the hybrid films.