Series Of Hybrid Materials Research Articles

A simple strategy for the construction of bi-supported triazine-based covalent organic frameworks as high-performance capacitive materials

A series of hybrid materials with different carbon nanotube contents TD-COF@CNTx (x = 0.05, 0.25, 0.45, and 0.65) were successfully prepared by using a one-pot method, where x represents the mass of carbon nanotubes added during the preparation process.

Transport Properties and Local Structure of an Imidazole/Protic Ionic Liquid Mixture Confined in the Mesopores of Hydrophobic Silica

The local structure and the molecular dynamics of an imidazole/protic ionic liquid mixture have been investigated while confined in only ca. 5 nm mesopores of silica particles. The walls of the silica pores were functionalized with trioctyl groups to ensure a hydrophobic character, and a series of hybrid materials with varying liquid-to-silica ratios were investigated. Results from vibrational spectroscopy (both Raman and infrared) indicate that the local ion–ion interactions as well as the nature of hydrogen bonds inside the nanopores are not significantly different from the case of the bulk liquid mixture. Nevertheless, the ionic conductivity decreases rapidly and monotonically with decreasing amount of liquid, while the self-diffusion coefficients measured by pulsed field gradient nuclear magnetic resonance (NMR) show a distinct dependence on composition. The population of molecules outside the particles seems to contribute with an enhanced diffusivity, while the molecules inside the mesopores diffuse at a rate comparable to that observed in the bulk liquid. In addition, when experimentally possible, we have measured higher diffusivities for the exchangeable −NH proton than for any other molecular species, which is indicative of a decoupled proton motion. Results from X-ray scattering, employed to elucidate the local molecular structure, reveal an additional feature characteristic of the nanoconfined state, which is associated with a real space distance of about 3.5 nm. This distance describes a specific molecular organization inside the mesopores and may reflect the formation of a monolayer of the octyl-imidazolium cations self-assembled at the hydrophobic silica surface. Such a local structure would favor the localization of charges, including the exchangeable protons. In addition, the analysis of molar conductivity suggests that a major problem with a low pore filling is the emergence of discontinuities throughout the liquid phase.

Hybrids of [C4mim]3+xPMo12−xVxO40: A new catalyst for oxidation of benzyl alcohol to benzaldehyde in water with greatly improved performances

A series of hybrid materials ([C4mim]3+xPMo12−xVxO40, x=0, 1, 2) based on V-substituted phosphomolybdic acid H3+xPMo12−xVxO40 (x=0, 1, 2) and ionic liquid 1-butyl-3-methyl imidazolium bromide ([C4mim]Br) have been prepared by anion-exchange method. The samples were well characterized by X-ray diffraction, Fourier transform infrared spectrophotometry and UV–Vis diffuse reflectance spectra analysis. The catalytic performances of the samples were tested in oxidation of benzyl alcohol to produce benzaldehyde using H2O2 as oxidant in water. The results have shown that the hybrids [C4mim]3+xPMo12−xVxO40 exhibit much higher catalytic properties than both the corresponding moieties. Especially, under the optimized conditions, 34% of benzyl alcohol conversion and 99% of selectivity for benzaldehyde have been obtained in the case of [C4mim]4PMo11VO40. The sample also exhibits good reusability and has been reused five runs without much decrease in conversion and selectivity.

Synthesis, characterization and catalytic evaluation of H3PW12O40 included in acrylic acid/acrylamide polymer for the selective oxidation of sulfides

A series of hybrid materials (SAPTPA) based on tungstophosphoric acid H3PW12O40 (TPA) included in acrylic acid/acrylamide polymer (SAP) were synthetized. The samples were characterized by FT-IR, XRD, 31P MAS-NMR, DTA-TGA, and the acidic properties were determined by means of potentiometric titration with n-butylamine. Materials with 10, 20, 30 and 40% (w/w) TPA content in the solid (SAPTPA10, SAPTPA20, SAPTPA30 and SAPTPA40, respectively) were prepared by impregnating the polymer with tungstophosphoric acid water solutions. According to FT-IR and 31P MAS-NMR studies, the main species present in the samples is the [PW12O40]3− anion, which was partially transformed into [P2W21O71]6− and [PW11O39]7− anions during the synthesis and drying steps.Taking into account XRD results, these species are highly dispersed in the polymer matrix or appear as noncrystalline phases. The DTA-TGA results show that SAPTPA materials did not undergo any remarkable chemical changes up to 200°C. Additionally, the SAPTPA materials showed strong acid sites whose number increased as the TPA content in them was higher.The materials obtained by impregnation of TPA onto the polymer matrix present suitable physicochemical properties to be used as catalysts in the selective oxidation of sulfides to the corresponding sulfoxide/sulfone using acetonitrile as solvent and H2O2 35% w/v as a clean oxidant.The SAPTPA40 catalyst was appropriate for the selective sulfide oxidation in heterogeneous conditions and can be reused without significant loss of its catalytic activity. A convenient and selective procedure for oxidizing sulfides to sulfoxides or sulfones by varying the H2O2/substrate ratio and the temperature was found.

Design and Integration in Electro‐Optic Devices of Highly Efficient and Robust Red‐NIR Phosphorescent Nematic Hybrid Liquid Crystals Containing [Mo6I8(OCOCnF2n+1)6]2− (n = 1, 2, 3) Nanoclusters

By combining [Mo6I8(C n F2n+1COO)6]2‐ (n = 1, 2, 3) nanocluster units with liquid crystalline ammonium cations, a new series of hybrid materials is developed that show a nematic liquid crystal phase, the most fluid of all LC phase, on a large range of temperatures including room temperature. The photophysical studies performed in the LC state show that these self‐assembled hybrid materials emit in the red‐NIR with absolute quantum yields up to 0.7 and show a very good photostability under continuous irradiation. They are further integrated up to 20 wt% in E7, a well‐known nematic commercial LC mixture. Mixtures are investigated in terms of homogeneity and stability to select the best suitable candidate for the design of electro‐controlled devices. Studies of optical switching, contrast, viscosity, and behavior toward an electrical stimulus demonstrate the high potential of these hybrid materials in the fields of photonic or optoelectronic.

Preparation and studies on properties of porous epoxy composites containing microscale hollow epoxy spheres

In this work, a series of porous epoxy composites containing microscale, hollow epoxy spheres were synthesized and characterized. First, microscale epoxy spheres were produced using amino-modified silica (AMS) particles with diameters of ∼1μm through a base-catalyzed sol–gel route. The as-synthesized AMS particles were then characterized through Fourier-transform infrared, 13C nuclear magnetic resonance (NMR), and 29Si-NMR spectroscopy. The prepared core–shell particles were immersed into a 1wt.% of HF solution for 24h to remove the inner part of the silica core, leading to the formation of hollow spheres of epoxy with a wall thickness of ∼100nm. These hollow epoxy spheres (HES) were characterized by scanning electron microscopy (SEM), Transmission electron microscopy, and thermogravimetric analysis (TGA). Finally, a series of hybrid materials was synthesized by performing thermal ring-opening polymerization reactions of epoxy resin in the presence of as-synthesized HES. Based on SEM observations on the morphology, the HES showed good dispersion capability in the polymer matrices, which led to a significantly reduced thermal conductivity and slightly decreased dielectric constant based on the transient plane source and LCR measurements, respectively. For example, the thermal conductivity and dielectric constant decreased by 49.3% and 12.6%, respectively, in the porous epoxy material synthesized with a final HES loading of about 10%. One possible reason was the large amount of air present in the material. Other physical characteristics such as the thermal and mechanical properties based on the results of TGA, differential scanning calorimetry, and dynamic mechanical analysis were investigated.

Functional processing of PET fabrics using boehmite/silica/thiazole dye hybrid materials

A series of hybrid materials composed of boehmite/silica/thiazole dyes and prepared via the sol-gel process is synthesized from aluminum isopropoxide (AIP) and tetraethoxysilane using heteroaryl 2-amino-thiazole azo dyes. Heterocyclic 2-amino-thiazole azo dyes undergo a hydrolysis-condensation reaction with an appropriate proportion of AIP under a catalyst, at a constant ratio of vinyltriethoxysilane (VTES) and tetraethoxysilane (TEOS). The structures of these hybrid materials composed of boehmite/silica/thiazole dyes are characterized using Fourier transform infrared (FT-IR) analysis. The surface morphology of polyethylene terephthalate (PET) fabrics is evaluated using scanning electron microscopy (SEM). SEM images show uniform dyeing of the PET fabrics that confirms the reaction of the hybrid materials with the PET fabrics. The water contact angle, washing fastness, color evenness, air permeability, and warmth retention of the PET fabrics dyed with hybrid materials composed of boehmite/silica/thiazole dyes are evaluated. The evaluation results indicate improved warmth retention property and good water repellency.

Preparation and Properties of Cage-Like Octaaminopropyl Polyhedral Oligomeric Silsesquioxane/Polyvinyl Alcohol Hybrid Materials

A series of hybrid materials involving cage-like octaaminopropyl polyhedral oligomeric silsesquioxane and Polyvinyl alcohol(OAPS/PVA) were prepared via solution blending method. The hybrid systems were characterized by FT-IR, scanning electronic microscopy(SEM), energy dispersive X-ray(EDS), differential scanning calorimetry(DSC), thermogravimetry analysis(TGA) and tensile test. The results show that hydrogen bond interactions are formed between OAPS and PVA and OAPS has a good dispersion in PVA matrix. The glass transition temperature(Tg) of OAPS/PVA increases from 53°C to 61°C, while the melting temperature(Tm) decreases from 180°C to 173°C with increasing OAPS content from 0% to 12%. The thermal stability of PVA main chain is improved by the addition of OAPS and the residue ratio also increases. The tensile strength of OAPS/PVA decreases from 39MPa to 16MPa, while the elongation at break of hybrid films increases from 148% to 351%.

Supported Neodymium Catalysts for Isoprene and rac‐β‐Butyrolactone Polymerization: Modulation of Reactivity by Controlled Grafting

A series of hybrid materials, bearing neodymium silylamide initiating groups, have been shown to mediate isoprene polymerization when combined with alkyl aluminum activators [methylaluminoxane, AlEt(2)Cl, Al(iBu)(3)]. The surface species nature and relative distribution were correlated with isoprene polymerization activity and selectivity. This approach to stereocontrol modulation has been extended to racemic β-butyrolactone isoselective ring opening polymerization.

Preparation of Heat-Resistant Epoxy/Silica Hybrids through a Novel Sol-Gel Process

A series of hybrid materials based on the diglycidyl ether of bisphenol-A (DGEBA) and 3-glycidoxypropyltrimethoxysilane(GPTMS) were prepared via a modified sol-gel process. The curing process of hybrid materials was analyzed with an advanced rheometric expansion system (ARES) and differential scanning calorimetry (DSC). Dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) were carried out to evaluate the thermal properties of the resulted epoxy hybrids. Copper clad laminates were also prepared by a traditional hot-press moulding procedure with the hybrid varnish, which showed an excellent heat-resistant performance This kind of hybrid material may be suitable for electronic applications due to their excellent high temperature reliability and stability.

Multiarm Cyclam-Grafted Mesoporous Silica: A Strategy to Improve the Chemical Stability of Silica Materials Functionalized with Amine Ligands

We have explored in this work the stability and the reactivity of multiarm cyclam-grafted mesoporous silica samples in aqueous solution. A series of hybrid materials have been prepared by grafting silylated cyclam molecules bearing one, two, or four silyl groups onto both amorphous silica gel (K60) and ordered mesoporous silica (SBA15). Under these conditions, cyclam moieties are attached to the silica walls via one, two, or four arms. Various physicochemical techniques have been applied to characterize the functionalized solids (elemental analysis, 1H-29Si and 1H-13C CPMAS NMR, and N2 adsorption-desorption isotherms). The interest in two and four arms for improving the chemical stability in solution, by comparison with the system displaying only one arm, has been demonstrated by using a set of complementary experiments involving pH measurements and silicon determination with ICP-AES. Then, the investigation of their protonation and binding properties toward copper(II) has revealed a significant decrease in the reactivity of these hybrids as a consequence of multiarm tethering. A comparison of amorphous and ordered materials has permitted us to point out the influence of mesostructuration on the reactivity of these functionalized solids, especially from a kinetic point of view.

Preparation and properties of amino-terminated anionic waterborne-polyurethane–silica hybrid materials through a sol–gel process in the absence of an external catalyst

A series of polymer–silica hybrid materials consisting of amino-terminated anionic waterborne-polyurethane (WPU) and inorganic silica particles have been prepared through a sol–gel process in the absence of an external catalyst. Typically, amino-terminated anionic WPU was first synthesized from polycaprolactone, dimethylol propionic acid, and 4,4′-methylenebis(cyclohexyl isocyanate) with specific molar ratios, followed by further reaction with triethylamine and triethylene tetramine to give as-prepared WPU. The WPU obtained was characterized by FTIR spectroscopy and gel permeation chromatography. Subsequently, a series of hybrid materials with different silica contents were prepared by performing sol–gel reactions with tetraethyl orthosilicate (TEOS) in an amino-terminated WPU matrix without the addition of an external catalyst. This was followed by examination by transmission electron microscopy and 29Si solid-state NMR. The terminated primary amine groups attached to the as-prepared WPU chains functioned as an internal base catalyst for the sol–gel process of TEOS. The effect of composition on the thermal stability, mechanical strength, surface wettability, and optical clarity of the hybrid materials was evaluated by the thermogravimetric analysis, dynamic mechanical analysis, contact angle measurement, and UV–visible transmission spectroscopy, respectively.

Hydrolysis, polycondensation, and catalytic properties of Ru(II) complex of 3‐4,5‐dihydroimidazol‐1‐yl‐propyltriethoxysilane

AbstractThe preparation and measurements of some properties of organic–inorganic hybrid materials derived from Ru(II)‐3‐4,5‐dihyroimidazol‐1‐yl‐propyltriethoxysilane inside a polysiloxane network have been achieved. The hydrolysis and polycondensation of Ru(II)‐3‐4,5‐dihyroimidazol‐1‐yl‐propyltriethoxysilane were performed in different experimental conditions, producing a new organic–inorganic silica. The alkoxysilyl groups available were used for the construction of inorganic backbone by the sol‐gel process, and the imidazole group was found suitable for incorporating Ru(II) by coordination. The coordination of metal complex is retained because there is no leaching from the metal complex containing gels. To ensure sufficient catalytic properties, a series of hybrid materials from tetraethoxysilane was prepared. These materials were identified and catalytic activities were tested for cyclization of (Z)‐3‐methylpent‐2‐en‐4‐yn‐1‐ol to 2,3‐dimethylfuran. Heterogeneous Ru(II) catalyst can also be recycled and reused without significant loss of selectivity or activity. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1329–1334, 2001

STRUCTURE AND SEGMENTAL DYNAMICS HETEROGENEITY IN HYBRID POLYCYANURATE-POLYURETHANE NETWORKS

Structure and segmental dynamics (at 140–600 K) in a series of hybrid materials with regularly varied composition, based on polycyanurate (PCN) networks and linear polyurethane (PUR), were studied by infrared spectroscopy, small-angle X-ray scattering, differential scanning calorimetry, and laser-inter-ferometric creep rate spectroscopy (CRS) techniques. Hybridization effect via cyanate/urethane group chemical interaction was evidenced in these systems and that led to formation of a completely homogeneous structure on a scale of > 2 nm, irrespective of material composition. At the same time, combined CRS/differential scanning calorimetry analysis indicated the pronounced nanoscale (≤ 2 nm) dynamic heterogeneity within or below the extraordinarily broad glass transition in these single-phase materials. Discrete CRS analysis of constituent motions, associated with the predicted kinds of polyurethane segmental relaxations (cooperative and noncooperative) and with the dynamics in differently cross-linked PCN network sections, has been performed.

Synthesis and catalytic properties of arene complexes of ruthenium(II) prepared from Si, Zr, Ti and Al alkoxides by the sol-gel process

Methods of synthesizing materials for catalysis were developed by synthesizing eta;-arene complexes of ruthenium(ii) coordinated to vinylpyridine that was followed by sol-gel polymerization with 3-methacryloxypropyltriethoxysilane. To enforce sufficient catalytic properties, a series of hybrid materials from Si, Zr, Ti and Al alkoxides were prepared by co-condensation. The hydrolysis and polycondensation of materials were performed at different experimental conditions. The monomeric compounds were identified and catalytic activities were tested for cyclization of (Z)-3-methylpent-2-en-4-yn-1-ol to 2,3-dimethylfuran.