Synthesis and characterisation of elastomeric composites prepared from epoxidised styrene butadiene rubber, 3-aminopropyltriethoxysilane and tetraethoxysilane

Hybrid composite materials were obtained by the reaction of epoxidised styrene butadiene rubber with 3-aminopropyltriethoxysilane, followed by in situ hydrolysis and polycondensation of tetraethoxysilane (TEOS). The hybrid films were characterised by thermogravimetric analysis, differential scanning calorimetry, swelling and stress–strain measurements, scanning electron microscopy and infrared spectrometry. Non-solubility of the films in tetrahydrofuran indicated the formation of a network, the microstructure of which varied according to the concentrations of the inorganic precursors employed. The thermal stabilities of the films were similar to that of rubber, and the mechanical stress increased considerably with the amount of silica incorporated. The most transparent films were those prepared with the lowest concentrations of inorganic precursors, whilst those obtained using larger amounts of TEOS showed distinct microscopic phases. The protocol described represents a simple method by which to bind inorganic precursors to rubbers.     

Continuous silica coatings on glass fibers via bioinspired approaches

Simple methods for producing continuous inorganic coatings on fibers have application in multiple technologies. The application of bioinspired strategies for the formation of particulate inorganic materials has been widely investigated and provides routes to inorganic materials under environmentally benign conditions. In this work, we describe the formation of stable and continuous inorganic coatings on glass fibers via the polymerization of silica in the presence of biopolymers. The formation of both organic and inorganic coatings was investigated via X-ray photoelectron spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray analysis. The simple route to silica coatings presented herein could be interesting for the development of functional hybrid fibrous materials suitable for catalytic and sensor applications, given the homogeneous nature of the silica films and the benign conditions employed for film formation.     

Reinforcement of polystyrene by covalently bonded oxo-titanium clusters

Oxo-metallic clusters are employed as inorganic nanobuilding blocks in order to obtain new organic–inorganic hybrid materials. Nanobuilding blocks are well-defined preformed entities which allow a better control of the inorganic domains for the elaboration of hybrid compounds. The oxo-alcoxo cluster Ti₁₆O₁₆(OEt)₃₂ presents a shell of labile ethoxy groups which can be selectively exchanged with the preservation of the oxo-core in order to introduce polymerizable ligands at the surface of this nanobrick. Three different new clusters, Ti₁₆O₁₆(OEt)_32−x(OPhCHCH₂)_x, have been synthesised, each cluster bears exactly 4, 8 and 16 styrenic groups. These functional clusters were copolymerized with styrene leading to three dimensional networks where the inorganic nano-fillers are covalently linked to the organic polymer. Thus new hybrid materials can be obtained and these nanobricks are good models to correlate the structure of hybrid materials and their physical properties especially their mechanical and thermal properties. The structure of the materials in function of the organic–inorganic ratio and in function of the cluster functionalities was investigated by SAXS, and the formation of the different levels of aggregation is reported.     

Epoxide Opening versus Silica Condensation during Sol–Gel Hybrid Biomaterial Synthesis

Hybrid organic–inorganic solids represent an important class of engineering materials, usually prepared by sol–gel processes by cross‐reaction between organic and inorganic precursors. The choice of the two components and control of the reaction conditions (especially pH value) allow the synthesis of hybrid materials with novel properties and functionalities. 3‐Glycidoxypropyltrimethoxysilane (GPTMS) is one of the most commonly used organic silanes for hybrid‐material fabrication. Herein, the reactivity of GPTMS in water at different pH values (pH 2–11) was deeply investigated for the first time by solution‐state multinuclear NMR spectroscopic and mass spectrometric analysis. The extent of the different and competing reactions that take place as a function of the pH value was elucidated. The NMR spectroscopic and mass spectrometric data clearly indicate that the pH value determines the kinetics of epoxide hydrolysis versus silicon condensation. Under slighly acidic conditions, the epoxy‐ring hydrolysis is kinetically more favourable than the formation of the silica network. In contrast, under basic conditions, silicon condensation is the main reaction that takes place. Full characterisation of the formed intermediates was carried out by using NMR spectroscopic and mass spectrometric analysis. These results indicate that strict control of the pH values allows tuning of the reactivity of the organic and inorganic moities, thus laying the foundations for the design and synthesis of sol–gel hybrid biomaterials with tuneable properties.     

Synthesis of new lamellar materials by self-assembly and coordination chemistry in the solids

We report the preparation of a new class of lamellar hybrid organic–inorganic materials obtained by self-assembly of bridged organosilica precursors containing long alkylene chains during the sol–gel process. The self-assembly is induced by lipophilic van der Waals interactions. The introduction of –SS– bonds in the core of the alkylene chains permitted the functionalisation of lamellar materials, which were subsequently transformed into SH and –SO₃H groups. This methodology was extended to the formation of lamellar hybrid materials containing amino groups thanks to CO₂ as bridging groups as well as the formation of lamellar hybrid materials containing carboxylic groups. In this last case, the hydrolysis and polycondensation of cyanoalkyltrialkoxysilanes permitted the one pot synthesis of lamellar hybrid materials thanks to in situ hydrogen bonds formation between carboxylic acids groups. All these functional lamellar materials exhibit a very high chelating capability towards transition metal and lanthanide ions.     

Properties of hybrid materials incorporating tetrabutyl titanate and tetraethoxysilane with ethylene-propylene nonconjugated diene terpolymer (EPDM-ENB) via sol-gel process

New flexible hybrid materials had been synthesized successfully by incorporating ethylene-propylene nonconjugated diene terpolymer (EPDM—ENB), which had been functionalized with 3-aminopropyl trimethoxysilane (APS), with highly reactive tetrabutyl titanate and tetraethoxysilane. The materials with low inorganic content displayed high transparency due to the formation of covalent bonds between the polymer chains and the inorganic network in the hybrids. The titanium systems were found to be more compatible than the corresponding silica hybrid materials of equal alkoxide content. As the inorganic content increased, the dynamic tensile modulus of the hybrid showed significant improvement over pure EPDM—ENB in the region above T_g of EPDM—ENB. For the EPDM—ENB/TiO₂ hybrids, when the total metal alkoxide content is fixed, the properties of the hybrids were not affected by partial replacement of tetrabutyl titanate with tetraethoxysilane. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2403–2409, 1997     

Pyrolyse des schistes bitumineux marocains (Tarfaya): etude de l'influence de la matrice minerale

Pyrolysis of Tarfaya, Morocco, oil shales: study of the influence of the inorganic matrix. The effects of the inorganic matrix of the oil shale on the pyrolysis of the Tarfaya oil shale were investigated using a modified Fisher - assay type apparatus. Experiments were conducted on the oil shale as well as on the kerogen isolated from the shale following a demineralization process. The results obtained show that the inorganic matrix retains the pyrolysis products, slows their formation and catalyzes the reactions leading to oil formation. The evacuation of the oil follows a diffusion process across the different pores and cracks of the mineral matrix. Pyrolysis of the oil shale resulted in higher oil yields when compared with the pyrolysis of the kerogen. In addition, the obtained oils are, in this case, more maltenique, more aromatic and less polar.     

Preparation and properties of poly(styrene-co-maleic anhydride)/silica hybrid materials by the in situ sol–gel process

Poly(styrene-co-maleic anhydride)/silica hybrid material has been successfully prepared from styrene–maleic anhydride copolymer and tetraethoxysilane (TEOS) in the presence of a coupling agent (3-aminopropyl)triethoxysilane (APTES) by an in situ sol–gel process. It was observed that the gel time of sol–gel solution was dramatically influenced by the amount of APTES. The hybrid material exhibits optical transparency almost as good as both silica gel and the copolymer. The covalent bonds between organic and inorganic phases were introduced by the aminolysis reaction of the amino group with maleic anhydride units of copolymer to form a copolymer bearing trimethoxysilyl groups, which undergo hydrolytic polycondensation with TEOS. The differential scanning calorimetry (DSC) showed that the glass transition temperature of the hybrid materials increases with increasing of SiO₂ composition. Photographs of scanning electron microscopy (SEM) and atomic force microscopy (AFM) inferred that the size of the inorganic particles in the hybrid materials was less than 20 nm. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1607–1613, 1998     

UV curing of organic–inorganic hybrid coating materials

The effect of UV-curing time on the mechanism of interaction between the various precursor phases in a novel sol–gel-derived organic–inorganic hybrid coating material and the resulting mechanical and thermal properties of this material when coated onto substrates in thin film form have been examined using a variety of chemical and physical characterisation methods. Microstructurally, the hybrid coating materials examined were all a single amorphous phase and were all optically transparent. The degree of interaction between the organic and inorganic phases, the scratch behaviour of the coating materials and the thermal stability of the coating materials were all found to depend strongly on the UV curing time. For the particular proportions of inorganic and organic components used to make up this hybrid coating material, an optimum UV curing time of 10 min under a UV intensity of 46.3 mW cm⁻² was found to produce transparent coatings which adhered well to the substrates and which were robust in scratch tests on aluminium and polycarbonate substrates and abrasion tests on polycarbonate substrates.     

Stimuli-sensitive core/shell template particles for immobilizing inorganic nanoparticles in the core

We synthesize and characterize stimuli-sensitive core/shell particles with functional group (or material) localized in the core. We previously reported two types of hybrid particles prepared by using the template particles which were synthesized by soap-free emulsion copolymerization with N-isopropylacrylamide and glycidyl methacrylate (GMA) as monomers but by different preparation methods. GMA has advantages in immobilizing materials having several functional groups such as thiol ones. In this study, to obtain the suitable template particles for immobilizing any inorganic nanoparticles in the core, we investigated the effect of feed ratio of the two monomers. Obtained template particles were modified by thiol compounds to introduce ionic groups. They were characterized by dynamic light scattering and scanning electron microscopy. After in situ synthesis of magnetic nanoparticles in the templates, the hybrid particles were characterized directly by transmission electron microscopy. Consequently, we could obtain the hybrid core/shell particles which contained a large amount of magnetic nanoparticles (∼33 wt%) in the core.     

Hybrid nanoflowers bearing tetraphenylporphyrin assembled on copper(II) or cobalt(II) inorganic material: A green efficient catalyst for hydrogenation of nitrobenzenes in water

Simple fabrication of organic–inorganic hybrid nanoflowers (TPP@CuhNfs and TPP@CohNfs) was achieved with tetraphenylporphyrin (TPP) as organic counterpart and Cu²⁺ or Co²⁺ ions as inorganic materials via a green route, with lower cost and controlled pH. The effect of pH levels and TPP concentrations on the morphology of the TPP@CuhNfs and TPP@CohNfs materials was examined by scanning electron microscopy (energy-dispersive X-ray [EDX]). The formation and chemical structures of TPP@CuhNfs and TPP@CohNfs were evaluated using Fourier transform infrared. Elemental analyses of these hybrid nanoflowers were carried out by EDX. The fabricated TPP@CuhNfs and TPP@CohNfs nanomaterials under optimum conditions act as effective reusable catalysts for the hydrogenation of nitroanilines in aqueous media at ambient temperature. The time-dependent hydrogenation can be easily monitored spectrophotometrically and verified by ¹H-nuclear magnetic resonance. These types of the catalytic reaction or system are recorded to be useful toward the hydrogenation of nitroanilines, regardless of the position and type of substrate. Moreover, TPP@CuhNfs and TPP@CohNfs catalysts demonstrated a type of metal ions-dependent catalytic efficiency toward hydrogenation of nitroanilines (organic pollutants), with TPP@CuhNfs found to be more effective than TPP@CohNfs. However, both catalysts containing Cu²⁺ and Co²⁺ ions showed good performance and can be reused at least five times without a significant decline in yield. The presented approach based on hybrid nanoflowers provides as a low cost and ecofriendly method (green route) for different catalytic hydrogenations.     

A fast convenient method to prepare hybrid sol-gel materials with low volume-shrinkages

We present a simple and fast method for the synthesis of polyacrylates-silica hybrid materials with significantly low volume shrinkages through the sol-gel reactions of tetraethyl orthosilicate and 2-hydroxyethyl methacrylate along with the free-radical polymerization of the acrylate monomer. The volume shrinkage from the processible sol to the final product was about 6–20% for the hybrid materials having the silica contents up to about 50 wt-%. As a result of the low shrinkage, crack-free, transparent and monolithic hybrid materials of relatively large sizes can be prepared within a short period of 6 to 12 hours. The formation of covalent bonding between the organic and the silica components in the hybrid materials was demonstrated. Thermal stability of the polyacrylate component in the hybrid materials were found to be higher than that of the bulk polymer. Other vinyl polymers such as poly(methyl methacrylate) and polyacrylonitrile have also been incorporated into the inorganic silica sol-gel matrix by using this method.     

Thermal degradation of epoxy-silica organic-inorganic hybrid materials

Degradation kinetics of organic-inorganic hybrid materials based on epoxy resin were investigated by thermogravimetric analysis (TGA). The hybrid materials were prepared from diglycidyl ether of bisphenol A (DGEBA) and 3-glycidyloxypropyltrimethoxysilane (GLYMO) polymerised simultaneously by poly(oxypropylene)diamine (Jeffamine D230). Nanometric level of homogeneity in the hybrids was verified by electron microscopy. Energy of activation of degradation for the hybrids with varying inorganic content, as well as for the unmodified epoxy-amine system, was determined by the isoconversional Kissinger-Akahira-Sunose method, and was found to be significantly higher for the hybrid materials than for the unmodified epoxy-amine system. The degradation process was described by empirical kinetic models. The results indicated that presence of the inorganic network influences the mechanism of degradation of organic phase. Greater thermal stability of hybrid materials was confirmed by other parameters obtained from TGA curves.     

Effect of graphite features on the properties of metal-organic framework/graphite hybrid materials prepared using an in situ process

Metal-organic framework (MOF)/graphite hybrid materials were prepared using an in situ process. Graphites with various chemical and physical features were used, and HKUST-1 was selected as the MOF component. The samples (parent materials and hybrid materials) were characterized by X-ray diffraction, nitrogen sorption, scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Then they were tested as ammonia adsorbents in dynamic conditions. The results indicate that the functionalization of graphite is important to build the hybrid materials with synergistic properties. The lack of functional groups on graphite results in the formation of a simple physical mixture. Besides the surface chemistry of the graphitic component, the physical parameters (porosity and size of flakes) also seem to influence the formation of the hybrid materials. It is observed that the graphite particles disturb the formation of HKUST-1 and induce a different crystal morphology (more defects and increased surface roughness) than the one observed when MOF is formed in the absence of a substrate. The latter behavior causes less ammonia to be adsorbed on the hybrid materials than is expected for the simple physical mixture of HKUST-1 and graphite. The MOF structure collapses (in HKUST-1 and the hybrid materials) upon ammonia adsorption and leads to the formation of new species.     

Luminescent thin films and nanoparticles of europium doped hybrids based on organosilyl 尾-diketonate

Novel organic–inorganic hybrid materials shaped as transparent films and core–shell nanoparticles were prepared by the sol–gel process from a new organo-alkoxysilane based on a β-diketonate (DBM-OH) and doped with trivalent europium ions. The resultant hybrid materials were characterized by Raman spectroscopy and electronic microscopy. Films thickness and nanoparticles size were respectively measured around 1?μm and 30?nm. The photoluminescence study, including the recording of excitation and emission spectra as well as the determination of the decay times, was investigated at room temperature. The results have pointed out an efficient ligand-to-Eu³⁺ intramolecular energy transfer resulting in a high quantum yield as determined by using an integrating sphere.     

Biaryl formation via Suzuki and Stille coupling reactions using palladium nanoparticle/polymeric N‐heterocyclic carbene grafted silica as recyclable and efficient catalyst

Palladium nanoparticles supported on polymeric N‐heterocyclic carbene grafted silica as an efficient organic–inorganic hybrid catalyst is introduced. Pd⁰ nanoparticle formation, which is stabilized by the polymeric N‐heterocyclic carbene ligands and ionic liquid units, was confirmed using X‐ray photoelectron spectroscopy. Scanning electron microscopy images showed microparticles of modified silica while transmission electron microscopy images displayed a fine distribution of Pd nanoparticles. The modified structure was applied successfully in biaryl formation via Suzuki and Stille coupling reactions. Various biaryls were generated through the reaction of phenylboronic acid or tetraphenyltin with a variety of haloarenes via cross‐coupling reactions. This catalyst showed promising activity after being recycled several times. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis,characterization and performance of nanosized Bi<Subscript>0.1</Subscript>Sn<Subscript>0.9</Subscript>O<Subscript>2</Subscript>–WPU organic–inorganic hybrid coatings

A series of organic–inorganic hybrid coatings consisting of organic waterborne polyurethane (WPU) and inorganic nanosized bismuth-doped tin dioxide were successfully synthesized by the in situ polymerization approach. Bi_0.1Sn_0.9O₂ nano-powders were prepared via a new route of sol–gel combustion hybrid method using acetylene black as the fuel. The formed nano-powders were characterized by transmission electron microscopy and X-ray diffraction (XRD). Bi_0.1Sn_0.9O₂–WPU was then fabricated with isophorone diisocyanate, 2,2-bis(hydroxymethyl) propionic acid and nano-Bi_0.1Sn_0.9O₂-poly(ε-caprolactone) (PCL) as the starting materials. Organic–inorganic hybrid coatings are always achieved with adjustable contents of Bi_0.1Sn_0.9O₂. The hybrid coatings with Bi_0.1Sn_0.9O₂ loading on the glass substrate exhibited good heat insulation efficiency. The tensile strength and breaking extensibility of nanocomposite film containing 1.0% of the nano-Bi_0.1Sn_0.9O₂ were measured as 9.35 MPa and 248%, respectively. The transmittance of visible light was above 80%. The heat insulation of glass coated with nano-Bi_0.1Sn_0.9O₂–WPU hybrid was over 60 °C in contrast to the commercial blank glass.     

An Organic/Inorganic Hybrid Polymer

Poly(N-acetylethylenimine) (polyoxazoline) (POZO) with a terminal triethoxysilyl group was successfully synthesized by the ring-opening polymerization of 2-methyl-2-oxazoline followed by termination with 3-aminopropyltriethoxysilane. Triethoxysilyl-terminated telechelic POZO was prepared by using a bifunctional initiator. These silane coupling POZOs were subjected to acid-catalyzed cohydrolysis polymerization with tetraethoxysilane by the so-called “sol-gel” method to produce a novel organic/inorganic hybrid polymer (block copolymer), which was a homogeneous transparent/glassy composite material. The obtained hybrid showed higher hydrophilic properties compared with silica gel without POZO segments. On the other hand, a hybrid polymer consisting of poly(2-ethyl-2-oxazoline) and silica gel, which absorbed both water and organic solvents, showed amphiphilic properties. POZO segments were eliminated by pyrolysis of the present hybrid polymer to produce a silica with micropores.     

Self-assembly of polymer and molybdenum oxide into lamellar hybrid materials

We report on self-assembly of polymer and molybdenum oxide chains into a new class of lamellar hybrid materials. Aqueous ammonium molybdate and polyvinyl alcohol (PVA) or carboxymethyl cellulose (CMC) were used as the starting materials. Ammonium molybdate was hydrolyzed into layered molybdenum oxide under acidified conditions. The organic polymer chains and the inorganic molybdenum oxide layers self-assemble and pack into new hybrid composites. Scanning electron microscope (SEM) images and polarized microscopy show that these two new materials have typical lamellar structure. Transmission electron microscope (TEM) images show that the layer thickness is about 100 nm. X-ray diffraction (XRD) data confirm the formation of inorganic molybdenum oxide. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) data gave thermal behavior of these composites. The mechanism of this hybrid reaction and the templating function of polymers were discussed in this paper. A special entropy effect was discovered when polymer was used as guest species. This entropy effect makes polymers preferential candidates as guest species rather than small molecules when fabricating organic/inorganic layered hybrid materials. We believe that this opens a new way to create organic/inorganic hybrid superstructures.