Search results for "Base"
showing 10 items of 8362 documents
Linked Benzylamido-Cyclopentadienyl Ligands: Synthesis and Characterization of Alkyl Titanium Complexes
1997
Titanium complexes of the general type Ti(η5:η1-C5H4Si-Me2NCH2C6H3X2-2,5)Cl2 (XH, F), containing a linked benzylamido-cyclopentadienyl ligand, were prepared by reaction of Ti(η5-C5H4SiMe2Cl)Cl3 with lithium amide Li(NHCH2C6H3X2-2,5). A single-crystal X-ray structural analysis of Ti(η5: η1-C5H4SiME2NCH2C6H3F2-2,5)Cl2 revealed a conformation in the solid state in which the aryl ring is turned away from the metal center. Ti(η5:η1-C5H4SiMe2NCH2C6H5)Cl2 can be alkylated with a variety of reagents to form extremely sensitive complexes of the type Ti(η5-C5H4SiMe,2NCH2C6H5)R2 (RMe, CH2 C6H5, CH2SiME3, CH2CMe2C6H5). Reaction of Li2[C5Me4SiMe2NCH2C6H5] with TiCl3(THF)3 gave Ti(η5: η1-C5Me4SiMe2NCH2C6…
Photosensitive polyurethanes for optical record
2011
The method of synthesis of photosensitive polyurethanes polymers on glycerine, toluenediisocyanate and Disperse Red 1 base has been described. Two types of polymers with different amount of Disperse Red 1 fragments in macromolecules were compared. Films of the polymers were obtained from solutions in organic solvents on glass substrate. The dry film thickness was in the range of 3,5 - 4.5 μm. The transmission spectrums of the films were studied. Possibility of formation of side product in the process of synthesis was observed. The photobirefringence measurements of polymers films were performed. Surface relief grating (SRG) formation was observed during polarization holographic recording pr…
Photolysis of Adsorbed Phases: Ethanoic Acid-Insulators and Semiconductors Systems. Influence of Acid-Base Properties.
1986
The paper reports the results of experiments in which the photodecomposition of adsorbed ethanoic acid (and in few cases of adsorbed acetone and ethanol) was carried out by using several silica gel samples, whose properties were modified by adding oxidic dopants as γ-Al2O3, which is acidic in character, and MgO, which is mainly basic. Also the related system MgO-Al2O3 was investigated. Few IR spectra on selected pure specimens and on specimens containing adsorbed ethanoic acid were recorded with the aim of following the variation of the surfaces-adsorbate interaction with the variation of the acid-base properties. It was also of interest to compare the photoreactivity of insulators and semi…
The effect of pre-heating on monomer elution from bulk-fill resin composites
2020
Background The present study was aimed to evaluate the effect of pre-heating of bulk -fill resin composites on monomer elution from them. Material and Methods Three different types of resin composites were used including Tetric N-Ceram Bulk Fill, X-tra Fill and X-tra Base. 10 cylindrical samples were prepared from each resin composites. Before light curing, 5 samples were pre-heated until reaching 68˚C, then 5 other samples were polymerized at room temperature. After 24 hours, release of UDMA, TEGDMA and BIS-GMA monomers were measured by High-Performance Liquid Chromatography analysis. Data analysis was performed by two-way ANOVA test, Games-Howell and Sidak post hoc tests. Results Pre-heat…
Effect of over the counter mouthwashes with and without alcohol on sorption and solubility of bulk fill resins
2020
Background Composites sorption and solubility can be precursors of several chemical and physical processes, which lead to deleterious effects on the polymer structure. This study evaluated the effect of mouthwashes with and without alcohol on the sorption and solubility of conventional and low viscosity bulk fill resins. Material and Methods Four types of Bulk Fill resins (Filtek™ Bulk Fill, X-tra Fil, Filtek™ Bulk Fill Flow and X-tra Base) were submitted to the following mouthwashes: Listerine Cool Mint and Periogard (containing alcohol) and Listerine Zero and Periogard (alcohol-free). The specimens were stored in the mouthwashes for seven days. Solubility and sorption tests were performed…
Fast and continuous synthesis of nanostructured iron spinel in supercritical water: influence of cations and citrates
2014
International audience; Spinel iron oxide nanoparticles were obtained under supercritical water conditions in a continuous and fast (less than 10s) way by modifying the initial stoichiometric Fe II /Fe III molar ratio from (1/2) to (3/0), without base solution, and using citrates directly with iron precursors. This result opens the way of an economical and environmentally benign approach to synthesize superparamagnetic iron oxide nanoparticles (SPIONs) in important yields.
Iron oxide-based magnetic photocatalysts: Recent developments, challenges, and environmental applications
2021
Abstract Magnetic separation of the solid photocatalyst from the reacting suspension has received great interest in recent research because it offers a suitable way for removing and recycling the heterogeneous photocatalytic material particles preventing the agglomeration and sedimentation during and after their use. The use of iron oxides such as heterogeneous photocatalysts is an appropriate choice to obtain a suitable photocatalyst easily separable from the fluid. This chapter presents a detailed investigation of iron oxide-based magnetic photocatalysts (IOMPs). We will discuss the required conditions for the synthesis of these photocatalysts, followed by their applications for the remov…
Magnetically enhanced polymer-supported ceria nanocatalysts for the hydration of nitriles.
2020
The heterogeneous catalysis of the hydration of nitriles to amides is a process of great industrial relevance in which cerium(IV) oxide (also referred to as ceria) has shown an outstanding catalytic performance. The use of non-supported ceria nanoparticles is related to difficulties in the purification of the product and the recovery and recyclability of the catalyst. Therefore, in this work, ceria nanoparticles are supported on a polymer matrix either by synthesizing polymer particles by so-called Pickering miniemulsions while using ceria nanoparticles as emulsion stabilizers or, as a comparison, by in-situ crystallization on preformed polymer particles. The former strategy presents signif…
Block and graft copolymers of 2-oxazolines
1994
The cationic ring-opening polymerization of 2-oxazolines is known to be initiated by alkyl halides, Lewis acids and esters of strong acids. The polymerization proceeds by a living mechanism. Numerous block and graft copolymers have already been described. Recently it was found that chloroformates (R-O-CO-CI) are also useful initiators. The mechanism of the initiation and propagation is discussed. This type of initiators allows the synthesis of different novel two-block and three-block copolymers, star-shape polymers, and a graft copolymer with a polyvinylacetate backbone.