SYNTHESIS OF SIO2-TIO2 XEROGELS BY SOL-GEL PROCESS

in Journal of Sol-Gel Science and Technology (1995), 4(3), 179-185

A new method to synthesize SiO2-TiO2 gels by sol-gel process has been developed. This technique uses tetraisopropylorthotitanate [Ti(O'Pr)(4)] and tetraethylorthosilicate [TEOS]: they are mixed in the ... [more ▼]

A new method to synthesize SiO2-TiO2 gels by sol-gel process has been developed. This technique uses tetraisopropylorthotitanate [Ti(O'Pr)(4)] and tetraethylorthosilicate [TEOS]: they are mixed in the same solvent and then directly hydrolysed. This one-step reaction is possible because of the use of 2-methoxyethanol, a protic polar solvent. This alcohol plays two different specific roles: it acts as a solvent as well as a stabilizer of titanium alkoxide towards the hydrolysis-precipitation reaction. So, by an accurate adjustment of the quantity of methoxyethanol in the mixture, we can control the reactivity of the titanium precursor. Monolithic and transparent xerogels were obtained whatever the composition. Three monolithic SiO2-TiO2 gels containing 20, 50 and 75 mol% of TiO2 were prepared and studied in details. By using the TG-DSC analysis, we can follow the evolution of the loss of water and organic residues. The structural evolution of gels during calcination is characterized by IR spectroscopy and X-Ray diffraction. [less ▲]

Synthesis of stilbenoids via the Suzuki-Miyaura reaction catalysed by palladium N-heterocyclic carbene complexes

in Journal of Molecular Catalysis A: Chemical (2006), 257(1-2), 158-166

The Suzuki-Miyaura reaction of aryl halides with trans-2-phenylvinylboronic acid using a series of related in situ generated N-heterocyclic carbene palladium(II) complexes was studied in order to evaluate ... [more ▼]

The Suzuki-Miyaura reaction of aryl halides with trans-2-phenylvinylboronic acid using a series of related in situ generated N-heterocyclic carbene palladium(II) complexes was studied in order to evaluate the effect of ligand structure and electronics on the catalytic activity and to investigate the nature of the catalyst species. The nature of the substituents of the carbene ligand was found to be critical. Specifically, the presence of alkyl groups on the ortho positions of the phenyl substituents was a requisite for obtaining the most efficient catalyst systems. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

Synthesis of tadpole-shaped copolyesters based on living macrocyclic poly(epsilon-caprolactone)

in Polymer (2006), 47(26), 8406-8413

Synthesis of an asymmetric tadpole-shaped aliphatic copolyester consisting of a poly(epsilon-caprolactone) ring and two poly(L-lactide) tails was reported for the first time. First, a high molecular ... [more ▼]

Synthesis of an asymmetric tadpole-shaped aliphatic copolyester consisting of a poly(epsilon-caprolactone) ring and two poly(L-lactide) tails was reported for the first time. First, a high molecular weight cyclic PCL macroinitiator (Mn = 31,000) was prepared by intramolecular photocross-linking of "living" chains. Polymerization of L-lactide was resumed by the tin dialkoxide containing macrocycles, thus making the targeted tadpole-shaped copolyester available. A preliminary investigation of the crystallization of these copolyesters was carried out by differential scanning calorimetry and polarized optical microscopy. [less ▲]

Synthesis of Tetraalkyl(Pyrrolidine-2,2-diyl)bisphosphonates and 2,2-Bis(diethoxyphosphoryl)-3,4-dihydro-2H-pyrrole 1-Oxide; ESR Study of Derived Nitroxides

in Journal of Organic Chemistry (1998), 63(24), 9095-9099

Synthesis of Tetraalkyl (Pyrrolidine-2,2-diyl)bisphosphonates and 2,2-Bis(diethoxyphosphoryl)-3,4-dihydro-2Hpyrrole 1-Oxide; ESR Study of Derived Nitroxides

Synthesis of thermo-responsive poly(N-vinylcaprolactam)-containing block copolymers by cobalt-mediated radical polymerization

in Journal of Polymer Science. Part A-1, Polymer Chemistry (2012), 50(2), 400-408

Thermo-responsive block copolymers based on poly(N-vinylcaprolactam) (PNVCL) have been prepared by cobalt-mediated radical polymerization (CMRP) for the first time. The homopolymerization of NVCL was ... [more ▼]

Thermo-responsive block copolymers based on poly(N-vinylcaprolactam) (PNVCL) have been prepared by cobalt-mediated radical polymerization (CMRP) for the first time. The homopolymerization of NVCL was controlled by bis(acetylacetonato)cobalt(II) and a molecular weight as high as 46,000 g/mol could be reached with a low polydispersity. The polymerization of NVCL was also initiated from a poly(vinyl acetate)-Co(acac)2 (PVAc-Co(acac)2) macroinitiator to yield well-defined PVAc-b-PNVCL block copolymers with a low polydispersity (Mw/Mn = 1.1) up to high molecular weights (Mn = 87,000 g/mol), which constitutes a significant improvement over other techniques. The amphiphilic PVAc-b-PNVCL copolymers were hydrolyzed into unprecedented double hydrophilic poly(vinyl alcohol)-b-PNVCL (PVOH-b-PNVCL) copolymers and their temperature-dependent solution behavior was studied by turbidimetry and dynamic light scattering. Finally, the so-called cobalt-mediated radical coupling (CMRC) reaction was implemented to PVAc-b-PNVCL-Co(acac)2 precursors to yield novel PVAc-b-PNVCL-b-PVAc symmetrical triblock copolymers. [less ▲]

Synthesis of titanium dioxide nanoparticles by reactive DC magnetron sputtering

in Thin Solid Films (2009), 518

Nanometer-sized titanium dioxide (TiO2) particles were prepared on carbon substrates by reactive direct-current magnetron sputtering. By performing measurements with high resolution electron microscopes ... [more ▼]

Nanometer-sized titanium dioxide (TiO2) particles were prepared on carbon substrates by reactive direct-current magnetron sputtering. By performing measurements with high resolution electron microscopes, the mean nanoparticle diameter and the coverage fraction of the substrate by the nanoparticles (NPs) were measured at 19 nm and 30%, respectively. Moreover, electron diffraction analysis showed that the TiO2 NPs' crystalline structure on the carbon substrate was a mixture of anatase and rutile. Finally,we provided information on the TiO2 initial growth stage: crystalline NPs were formed after deposition of amorphous nanoparticles on the substrate and heating. [less ▲]

Synthesis of transition metal-doped carbon xerogels by solubilization of metal salts in resorcinol-formaldehyde aqueous solution

in Carbon (2004), 42(15), 3217-3227

The pore texture of carbon materials obtained from evaporative drying and pyrolysis of resorcinol-formaldehyde aqueous gels is controlled by the initial pH of the precursors solution. In order to produce ... [more ▼]

The pore texture of carbon materials obtained from evaporative drying and pyrolysis of resorcinol-formaldehyde aqueous gels is controlled by the initial pH of the precursors solution. In order to produce transition metal-containing carbons with tailored texture, various metallic salts were dissolved in the precursors solution. When necessary, a complexing agent (HEDTA or DTPA) was added to render the metal ions soluble. Ni, Fe and I'd loaded carbon xerogels were synthesized and their pore texture was studied after evaporative drying and after pyrolysis. The carbon texture was also studied with regard to the nature of the metal and the amount of complexing agent. The solubilization of transition metal salts in the resorcinol-formaldehyde aqueous solution does not prevent the texture regulation, even though this texture control is influenced: the limits of the pH interval leading to micro mesoporous carbon materials can slightly differ when a metal salt and/or a complexing agent are added. The pH range shift depends mainly on the amount and nature of the complexing agent, but also slightly on the nature of the metal ion. Nevertheless, the metal particles obtained are rather big (diameter > 15 nm). For catalytic applications, the metal dispersion must be enhanced, especially in the case of expensive metals. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

Synthesis of uronic acid derivatives bearing a single or two alkyl chains as new surfactants

Poster (2008, September)

Synthesis of water balance data and simulation of the shrinking process of the Aral Sea.

Conference (2001)

Synthesis of well-defined poly(alkyl methacrylate)-graft-polylactone by sequential living polymerization

in Macromolecular Chemistry and Physics (1999), 200(1), 156-165

A novel combination of living polymerization reactions has been proposed for the controlled synthesis of poly(alkyl methacrylate)-graft-polylactones. This strategy relies upon the sequential living ... [more ▼]

A novel combination of living polymerization reactions has been proposed for the controlled synthesis of poly(alkyl methacrylate)-graft-polylactones. This strategy relies upon the sequential living polymerization of alkyl methacrylates and aliphatic lactones, with an intermediate chemical transformation for shifting from the first mechanism to the second one. In the first step, an alkyl methacrylate (methyl and butyl) is copolymerized with 2-trimethylsiloxyethyl methacrylate (TMSEMA). This living anionic polymerization is initiated with diphenylhexyllithium( DPHLi) in the presence of a μ-ligand, lithium chloride, in THF at - 78 °C. The trimethylsiloxy groups are then hydrolyzed with release of hydroxyl groups which are reacted with triethylaluminum in order to form a multifunctional macroinitiator of the Al alkoxide type. The second step consists of the ring opening polymerization (ROP) of aliphatic lactones (ε-caprolactone, J-valerolactone and 1,4,8-trioxaspiro[4.6]-9-undecanone (TOSUO)) with the formation of novel graft copolymers. As a result of the livingness of both the anionic and the ROP polymerization steps, the molecular weight of both the main backbone and the grafts is predictable, the apparent polydispersity is narrow ( from 1.05 to 1.30) and the grafting density can be controlled being dependent on the distribution of the hydroxyl groups within the precursor backbone. [less ▲]