Hybrid Matrices Research Articles

Transient gate matrices of three-phase modelled power grids

A method of calculating transients in three-phase modelled power grids is presented. First, important devices are modelled by transient device admittance matrices. According to the configuration of the grid, these matrices are put together to form a transient node admittance matrix. Based on this result, transient gate impedance, admittance and hybrid matrices are derived. Their main properties are discussed.

Molybdenum oxide-organosilane hybrids through sol–gel process

From reactions between tetraethylortosilicate (TEOS) and nitrogen containing organosilanes of general formula (C 2H 5O) 3Si–R; R=–(CH 3) 2NH 2, –(CH 3) 2NH(CH 2) 2NH 2 and –(CH 3) 2NH(CH 2) 2NH(CH 2) 2NH 2, with lamellar molybdenum trioxide (α-MoO 3), four hybrid matrices, named here as MoSil, MoN1, MoN2 and MoN3, respectively, were synthesized, through sol–gel process. The obtained matrices were characterized by elemental analysis, Infrared spectroscopy, thermogravimetry, scanning electron microscopy, X-ray diffraction patterns, surface area measurements and 29Si CPMAS NMR spectroscopy. The organic moiety contents are 1.7, 2.0 and 0.9 mmol g −1 for MoN1, MoN2 and MoN3 matrices, respectively. The measured surface areas are 0.61; 78.12; 1.85; 0.59 and 2.53 m 2 g −1 for MoO 3, MoSil, MoN1, MoN2 and MoN3 matrices, respectively. Molybdenum oxide exhibts a single mass loss step in TG curve, due to the sublimation of the oxide, starting at 730 °C.The MoSil matrix exhibits a similar TG curve profile, but the thermal degradation takes place at 704 °C. MoN1, MoN2 and MoN3 matrices shows mass loss steps of 20%, 30% and 23%, respectively, associated with the organic moiety. The 2 θ values for the 001 diffraction plane were 12.64, 13.20, 12.82, 12.84 and 12.90° for MoO 3, MoSil, MoN1, MoN2 and MoN3 matrices, respectively, indicating that the organic species are at the surface, and not inside the interlayer space.

Enhancement of laser properties of pyrromethene 567 dye incorporated into new organic–inorganic hybrid materials

The incorporation of pyrromethene 567 dye into newly synthesized organic–inorganic hybrid materials, laser photostabilities were demonstrated, which are, to the best of our knowledge, the highest achieved to date for both inorganic and hybrid matrices doped with pyrromethene dyes. These results evidence that, in order to reach the necessary photostability for a solid-state dye laser being competitive with liquid dye lasers, hybrid matrices combine advantageous properties of inorganic materials, such as a high thermal dissipation capability, without losing the benefits of organic polymers.

Entrapment of rhodium complexes in inorganic or hybrid matrices via the sol–gel method

Rhodium complexes have been entrapped inside the porous systems of inorganic or hybrid matrices via the sol–gel method. The resulting materials were tested as catalysts in hydroformylation reactions. The microporous materials could be recycled without any rhodium leaching, being active even in the absence of a solvent. High turnover numbers were obtained in the hydroformylation of either 1-hexene or 1-decene. However, the characteristics of the matrix could not be related to the addition (or not) of a hybrid organic–inorganic co-condensation agent, but appeared to depend on the nature of the rhodium complex.

Fabrication of a novel porous PGA-chitosan hybrid matrix for tissue engineering

Polyglycolide (PGA) and chitosan mixture solution was prepared using solvents of low toxicity to create novel, porous, biocompatible, degradable, and modifiable hybrid matrices for biomedical applications. The porosity of these PGA-chitosan hybrid matrices (P/C matrices) was created by a thermally induced phase separation method. Two types of the P/C hybrid matrices containing 70 wt% PGA (P/C-1 matrix) and 30 wt% PGA (P/C-2 matrix) were fabricated. Chitosan matrix was also prepared for comparison. A 35-day in vitro degradation revealed that the weight losses for the P/C-1 and P/C-2 matrices were similar (∼61%), but the releases of glycolic acid from the P/C-1 and P/C-2 matrices were 95% and 60%, respectively. The P/C-1 matrix had higher porosity and higher mechanical strength than the P/C-2 and chitosan matrices. Fibroblast cells cultivated in these matrices proliferated well and the cell density was the highest in the P/C-1 matrix, followed by the chitosan and P/C-2 matrices, suggesting good biocompatibility for the P/C-1 matrix. We thereby concluded that the P/C-1 matrix, due to its high strength, porosity, biocompatibility and degradability, is a promising biomaterial. The presence of chitosan in the P/C matrices provides many amino groups for further modifications such as biomolecule conjugation and thus enhances the application potential of the P/C hybrid matrices in tissue engineering.

New organic-inorganic hybrid matrices doped with rhodamine 6G as solid-state dye lasers

We report on the laser action of rhodamine 6G (Rh6G) incorporated into new hybrid organic–inorganic monolithic materials. The synthesis of these materials proceeded via the simultaneous sol-gel process of the inorganic part (tetraethoxysilane or tetramethoxysilane) and the free-radical polymerization of an organic monomer part (2-hydroxypropyl methacrylate, 2-hydroxyethyl methacrylate and a 1:1 v/v copolymer of this monomer with methyl methacrylate). The wt. % proportion of the alkoxide was systematically varied in each organic formulation, and the effect of each organic–inorganic composition on the lasing properties of Rh6G was evaluated. The laser samples were transversely pumped and the influence on the laser action of dye concentration, pump wavelength and pump repetition rate was analyzed. Lasing efficiencies of up 26% and good stabilities, with a 90% drop in the initial laser output of up to 12000 pump pulses at 2.5 Hz, were obtained when the samples were pumped at 355 nm with 5.5 mJ/pulse from the third harmonic of a Q-switched Nd:YAG laser.

Optical Properties of Lanthanide Doped Hybrid Organic-Inorganic Materials

Sol-gel matrices have been investigated for some years as potential matrices for rare earth luminescence. Sm3+, Eu3+, Dy3+, Er3+ and Tm3+ optical properties in siloxane-zirconium hybrid matrices prepared at room temperature have been investigated. Even if luminescence efficiency is governed by non-radiative relaxation linked to hydroxyl groups, in these matrices, rare earth fluorescence is always observed but lifetimes and quantum yields are dependent on the elaboration procedure. Eu3+ is used as a probe of the local surrounding around the dopant and the emission and decay profiles measurements in rare earth doped and undoped matrices are presented.

Targeted Administration of Proteic Drugs. I. Preparation of Polymeric Nanoparticles

The formulation of hybrid nanoparticles based on synthetic polymer-protein hybrid matrices for the targeted release of proteic drugs with antiviral activity such as a-interferon was investigated. Human serum albumin, alone, or in combination with myoglobin, and the hemiesters of alternating copolymers of maleic anhydride/alkyl vinyl ethers of oligo(ethylene glycol) were selected as proteic and synthetic components, respectively. Digalactosyl diacyl gycerol, a natural glycolipid selectively recognized by the asialofetuin receptor was used for the active targeting of liver hepatocytes. Nanoparticle suspensions were prepared either by slow solvent evaporation from biphase and triphase emulsions or by controlled coprecipitation. Nanoparticles, 0.1-0.3 gm in diameter, were obtained by the latter method, whereas the former one afforded heterogeneous micro and nanoparticle mixtures. Several techniques were tested to separate the nanoparticle dispersions from the suspending solution. The best results, in terms of a homogeneous distribution of mostly spherical nanoparticles, were obtained by centrifugation in the presence of modified cyclodextrins. After lyophilization of supernatant, the resulting fluffy powder was easily resuspendable in water.

Stable sol-gel microstructured and microfluidic networks for protein patterning.

We demonstrate the formation of micropatterned sol-gel structures containing active proteins by patterning with polydimethylsiloxane (PDMS) microchannels. To transport sol solution efficiently into the hydrophobic PDMS microchannels, a hydrophilic-hydrophobic block copolymer was used to impart hydrophilicity to the PDMS microchannels. Poor adhesion of the micropatterned gel structure onto glass slides was improved by treating the glass surface with a polymeric substrate. To minimize cracks in the gel microstructure, hybrid matrices of interpenetrating organic and inorganic networks were prepared containing the reactive organic moieties polyvinylalcohol or polyvinylpyrrolidone. Retention of biochemical activity within the micropatterned gel was demonstrated by performing immunobinding assays with immobilized immunoglobulin G (IgG) antibody. The potential application of microfluidics technology to immobilized-enzyme biocatalysis was demonstrated using PDMS-patterned microchannels filled with trypsin-containing sol-gels. This work provides a foundation for the microfabrication of functional protein chips using sol-gel processes.

Preparation of Organic-Inorganic Multifunctional Nanocomposite Coating via Sol-Gel Routes

The inorganic–organic nanocomposite coatings are prepared on poly(methyl methacrylate) (PMMA) substrate by the spinning technique which involves incorporating homogeneously nanosized ZnO particle into the molecular inorganic–organic hybrid matrices. The hybrid matrices are derived from tetraethoxyasilane (TEOS) and 3-glycidoxypropyltrimethoxyailane (GLYMO). To avoid the destruction of the polymer structure caused by ZnO and modify the interface between nanoparticles and organic groups, ZnO was first surface-coated with SiO2 from hydrolyzed TEOS using ammonia water as catalyst. The coatings thus obtained are dense, flexible, abrasion resistant and UV absorbent.

Исследование механических свойств углепластиков с различными типами гибридных матриц при отрицательных температурах

The technology of creating specimens of carbon fiber reinforced plastic with different types of hybrid matrices is described, one of the components of which retains its viscoelastic state, and the second is completely cured during the molding process. Technical wax, anaerobic and organosilicon polymeric materials are accepted as viscoelastic components of the hybrid matrix. The results of mechanical tensile tests of these specimens, performed at temperatures t1 = 20 ± 2 °С and t2 = –30 °С are presented.

Sol-gel derived nanoparticles as inorganic phases in polymer-type matrices

The use of nanoparticles in hybrid and polymeric matrices has been investigated. Different types of nanocomposites have been prepared. The ormosil type based on organoalkoxy silanes shows surprising properties with respect to solid content and relaxation. Thick films for coatings, embossed films for diffractive purposes, high temperature stable binders for glass fiber insulation materials and printing pastes have been prepared. The nanomer type with nanoparticles homogeneously dispersed in polymer matrices led to optical adhesives with improved properties with respect to Tg and thermal coefficient of expansion. The inverse nanomer type with the nanoparticles forming a percolating network was developed for photo curable optical interference layers on plastic, for example to AR coating by using simple wet chemical coating techniques.

Chitosan/Calcium Phosphate Scaffolds for Bone Tissue Engineering

AbstractThis research involves synthesis and characterization of biodegradable 3-dimensional polymer/calcium phosphate hybrid matrices as scaffolds for bone tissue regeneration. The scaffolds are comprised of chitosan and calcium phosphates [β-tricalcium phosphate (β-TCP), invert glass] and have combined optimum mechanical and biological properties of the two materials. Chitosan is a biocompatible and biodegradable polymer, and has rich hydroxyl groups for surface modification. Calcium phosphate crystals and invert glass are used as powder fillers to reinforce the scaffolds and increase bioactivity of the scaffolds. The scaffolds are fabricated using a thermally induced phase separation technique. The principal advantages of this technique are its low cost, low shrinkage levels, low sintering temperatures, and its ability to produce a variety of microstructures of various shapes and sizes. The osteoblast-like MG63 cells are seeded on the scaffolds to study the attachment and proliferation of the cells. The hydroxyl groups on the scaffolds are used to graft arginine-glycine-aspartate (RGD) peptides for promoting bone cell attachment and new tissue formation.

Optical Limiting Devices Based on C60 Derivatives in Sol-Gel Hybrid Organic-Inorganic Materials

A guest-host solid state device based on hybrid organic-inorganic materials and fullerene derivatives has been fabricated for optical limiting applications. Different 3-glycidoxypropyltrimethoxysilane derived hybrid matrices have been synthesized to increase the optical limiting performances. These matrices have shown high laser damage fluences, low light scattering, good transmittance in the visible range and allowed to deposit 10–100 μm thick films per single layer. The C60 derivatives have been functionalized with Si tri-alkoxide terminal groups and have reached a final concentration in the solid matrix up to 2 × 10−2 M·l−1. A multilayer system with a bottleneck structure has been developed to optimize a laser protection device.

Kinetics of in vitro release of a model nucleoside deoxyuridine from crosslinked insoluble collagen and collagen–gelatin microspheres

The objective of this research is to investigate the effect of highly crosslinked insoluble collagen and collagen–gelatin hybrid matrices as platforms for controlled release of a highly water soluble model nucleoside, deoxyuridine as well as a high molecular weight model compound fluoroscienisothoicyanate (FITC)-dextran. Collagen and gelatin can be considered as biodegradable proteinous materials. Microspheres of deoxyuridine and FITC-dextran were prepared by emulsification solvent evaporation technique using collagen alone and collagen–gelatin combination. The microencapsulation efficiency, particle size and in vitro release profiles were compared. Microencapsulation efficiency of≈10% was obtained with collagen while 20% encapsulation efficiency was obtained when collagen was used in combination with gelatin. Particle size range became wider when only collagen was used as compared to collagen–gelatin combination. A slower release profile was observed for crosslinked as compared to noncrosslinked microspheres. This study demonstrated diffusion controlled release of both compounds from the two polymers used. A good correlation was obtained between theoretically predicted and experimentally obtained in vitro release rates for both deoxyuridine and FITC-dextran using Higuchi’s square root model.

Sol-Gel Processing of Organic-Inorganic Nanocomposite Protective Coatings

Organic-inorganic nanocomposite protective coatings are prepared on aluminum substrates by the spinning technique with the concept of incorporating homogeneously nanosized particles (of AlOOH, Al2O3, ZrO2, SiC) into molecular organic-inorganic hybrid matrices. The hybrid matrices are prepared from epoxysilane and bisphenol A with imidazol as catalyst. The AlOOH particles are derived from aluminum isoprooxide and introduced into the hybrid sols directly, and Al2O3, ZrO2, SiC particles are first surface-modified with Si–OH from hydrolyzed TEOS. The coatings are dense, smooth and flexible and inhibit corrosion.

Synthesis and Intermolecularly Mediated Assembly of Organic Pigment in Hybrid Coating Films

AbstractThe insoluble, strongly hydrogen bonded organic pigment of 3,6-bis-(4-chlorphenyl)-l,4- diketopyrrolo [3,4-c] pyrrole was transiently blocked by adding carbamate groups, and consequently incorporated into organic-inorganic hybrid matrices by a sol-gel process. The homo- (pigment-pigment) and hetero-intermolecular (pigment-matrix) interactions were found to control both the assembly and dispersion of pigment molecules in the hybrid coating films. A weaker interaction between matrices and pigment molecules results in aggregation of the carbamate pigment in the methyl-silicate films. A stronger interaction forms a homogenous dispersion and coloration of the phenyl-silicate films. The as-prepared methyl- and phenylsilicate films doped with the organic pigment were distinguished by a morphology change and a blue (hypsochromic) shift in absorption from 550 to 460 nm. Thermal treatment can remove the carbamate groups and in-situ form the organic pigment in the hybrid films.

Room temperature synthesis of hybrid organic–inorganic nanocomposites containing Eu2+

For the first time, the room temperature synthesis of new Eu2+ doped hybrid materials together with their absorption and emission properties are reported. These hybrids containing Eu2+ and a small amount of Eu3+ are obtained through the hydrolysis and condensation of diethoxymethylsilane, methyltriethoxysilane and zirconium tetrapropoxide precursors in the presence of europium trichloride. These Eu2+ doped materials exhibit a strong host dependent Eu2+ luminescence, the intensity of which does not change upon air storage, confirming that Eu2+ ions are efficiently trapped inside these hybrid matrices.

Epoxy-Polysulfone Networks as Advanced Matrices for Composite Materials

Compatibility between polysulfone (PSF) and epoxy oligomers in the melt state as well as the morphology and properties of alloys obtained were studied as a function of composition. The compatibility depends on the length and structure of epoxy molecules, and is best in the case of epoxysulfone oligomers (ESO). The properties of hybrid matrices are determined by their composition and morphology. The most pronounced effects are observed in the regions of small concentrations of either component. A small quantity of PSF significantly improves thermal stability and heat resistance of the epoxy resin as well as its impact strength. On the other hand, on addition to PSF of small amounts of epoxysulfone oligomers, the processability of the matrix can be substantially improved. In particular, the melt viscosity decreases, and wetting and impregnation of fibrous reinforcement is facilitated. Besides, the matrix adhesion to fibers is increased. Powdered PSF/ESO/curing agent mixtures are good for application in solvent-free technological processes of fibrous composites production, e.g. in electrostatic deposition of matrix particles onto a reinforcing fabric. Plastics based on hybrid matrices are distinguished by improved strength.

Solution conformation of an abasic DNA undecamer duplex d(CGCACXCACGC) x d(GCGTGTGTGCG): the unpaired thymine stacks inside the helix.

The three-dimensional structural analysis of DNA undecamer 5'd(C1G2C3A4C5X6C7A8C9G10C11)3', 3'd(G22C21G20T19G18T17G16T15G14C13G12)5' duplex in which the X residue is a modified abasic site [3-hydroxy-2-(hydroxymethyl)tetrahydrofuran] has been performed using NOESY, DQFCOSY, TOCSY, and 31P-1H HSQC-TOCSY spectra in relation with molecular dynamics simulations. A total of 249 distances and 224 dihedral angles were used for construction. The optimal distances were calculated using the complete relaxation matrix method from hybrid matrices which were built with the experimental NOE intensities and additional data derived from either standard A- or B-DNA. Six independent refined structures starting from canonical A- and B-DNA were determined on the basis of the NMR data, and all converged to a single family with average rms deviations below 0.6 A and final NOE Rx factors of 0.055 +/- 0.03. A satisfactory agreement was obtained between measured NOE intensities and those resulting from full relaxation matrix calculations. A single intrahelical form of right-handed DNA duplex is observed; the aromatic base of residue T17 opposite the abasic site is stacked inside the helix. No clear correlation was detected between the C5 and C7 residues, excluding their proximity and the looping out of the abasic site. The abasic site induces a kink of about 30 degrees in the DNA duplex. This kink allows the formation of a bifurcated hydrogen bond between the amino protons of C5 and the O4 oxygen of T17. A detailed analysis of the final structures and their comparison with previous studies of abasic site lesions are described.