Search results for "propylene carbonate"
showing 9 items of 19 documents
Organic carbonates as alternative solvents for asymmetric hydrogenation
2009
Organic carbonates like propylene carbonate (PC) or butylene carbonate (BC) belong to the class of aprotic, highly dipolar solvents (AHD). Interestingly, their potential as solvents for asymmetric catalysis has been overlooked for a long time. The aim of this work is to evaluate organic carbonates and other organic solvents like THF, CH2Cl2, and acetonitrile as well as members of the AHD-family (DMF, DMSO, etc.) as media for homogeneous asymmetric hydrogenation. For this reason cationic Rh-complexes based on chiral phosphine ligands were tested in the hydrogenation of typical benchmark substrates. In several trials, significant advantages of organic carbonates were found. In contrast to DMS…
Controlled Synthesis of Multi-Arm Star Polyether-Polycarbonate Polyols Based on Propylene Oxide and CO2
2013
Multi-arm star copolymers based on a hyperbranched poly(propylene oxide) polyether-polyol (hbPPO) as a core and poly(propylene carbonate) (PPC) arms are synthesized in two steps from propylene oxide (PO), a small amount of glycidol and CO2 . The PPC arms are prepared via carbon dioxide (CO2 )/PO copolymerization, using hbPPO as a multifunctional macroinitiator and the (R,R)-(salcy)CoOBzF5 catalyst. Star copolymers with 14 and 28 PPC arms, respectively, and controlled molecular weights in the range of 2700-8800 g mol(-1) are prepared (Mw /Mn = 1.23-1.61). Thermal analysis reveals lowered glass transition temperatures in the range of -8 to 10 °C for the PPC star polymers compared with linear …
MCM-41 silica effect on gel polymer electrolytes based on thermoplastic polyurethane
2012
Abstract Polymer electrolytes were prepared from thermoplastic polyurethane with addition of mixture of N-ethyl(methylether)-N-methylpyrrolidinium trifluoromethanesulfonimide (PYRA12O1TFSI) ionic liquid, lithium bis(trifluoromethanesulfoneimide) salt and propylene carbonate. MCM-41 mesoporous silica was added in proportions ranging from 5 to 20 wt.% with respect to TPU. The electrolytes were characterized by thermogravimetric analysis, differential scanning calorimetry, linear voltammetry and impedance spectroscopy. The MCM-41 addition to the system was found to improve the electrochemical stability of the membranes and to reduce the gel electrolyte/metallic Li interfacial resistance. The f…
Structural characterization of 2,2-di-n-butyl-4-methyl-1,3,2-dioxastannolane isolated from supercritical CO2 conditions
2009
The title compound has been isolated as single crystals from the synthesis of propylene carbonate from racemic 1,2-propanediol and carbon dioxide using n-Bu2SnO as a catalyst precursor. The X-ray crystallographic structure analysis revealed the self-assembly of di-n-butyltin(IV) 1,2-propanediolate units, linked together through long-distance Sn-O interactions leading to a one-dimensional polymeric architecture organized in a syndiotactic arrangement. The coordination geometry around the tin atoms can be described as an unusual faced-capped trigonal bipyramidal environment.
Electrochemical performance of Na2FeP2O7/C cathode for sodium-ion batteries in electrolyte with fluoroethylene carbonate additive
2022
Abstract Solution synthesis was used to prepare pristine Na2FeP2O7 and Na2FeP2O7/C composite cathode materials for sodium-ion batteries, using glucose as a carbon source. While the pristine Na2FeP2O7 displays capacity of only 45 mAh/g due to the relatively large grain size, the addition of carbon increases the capacity to up to 92 mAh/g (95% of the theoretical 97 mAh/g capacity) with excellent rate capability, as 44 mAh/g capacity is still retained even at 20 C (1.94 A/g) current. The optimal content of carbon was found to be 4.8%. The initial capacity of 81 mAh/g is fully retained after 500 cycles at 1 C, indicating excellent cycle life. Measurements were carried out in 1 M NaClO4 salt in …
Highly cross-linked imidazolium salt entrapped magnetic particles – preparation and applications
2012
Magnetic particles entrapped into highly cross-linked imidazolium salts were synthesized using a straightforward approach by radical polymerization of bis-vinylimidazolium salts in the presence of superparamagnetic iron oxide particles. Potential applications for these new materials as (i) catalysts for conversion of propylene oxide to propylene carbonate, (ii) supports for organocatalysts, and (iii) scavenger materials for palladium removal are outlined.
Novel electrolytes for electrochemical double layer capacitors based on 1,1,1,3,3,3-hexafluoropropan-2-ol
2012
Abstract 1,1,1,3,3,3-Hexafluoropropan-2-ol (HFIP) was tested for its applicability as solvent in electrolytes for energy storage devices. A comprehensive characterization with respect to solubility, conductivity, as well as chemical and electrochemical stability was carried out with different conducting salts. Furthermore, different HFIP solutions containing standard supporting electrolytes and alkali metal fluorides, respectively, were applied in electrochemical double layer capacitor cells. Their behavior was studied with impedance spectroscopy and cyclic voltammetry at low scan rates and compared to the current benchmark electrolytes based on propylene carbonate (PC) and acetonitrile (AN…
CO2-Based Non-ionic Surfactants: Solvent-Free Synthesis of Poly(ethylene glycol)-block-Poly(propylene carbonate) Block Copolymers
2013
Copolymerization of carbon dioxide (CO2) and propylene oxide (PO) is employed to generate amphiphilic polycarbonate block copolymers with a hydrophilic poly(ethylene glycol) (PEG) block and a nonpolar poly(propylene carbonate) (PPC) block. A series of poly(propylene carbonate) (PPC) di- and triblock copolymers, PPC-b-PEG and PPC-b-PEG-b-PPC, respectively, with narrow molecular weight distributions (PDIs in the range of 1.05–1.12) and tailored molecular weights (1500–4500 g mol−1) is synthesized via an alternating CO2/propylene oxide copolymerization, using PEG or mPEG as an initiator. Critical micelle concentrations (CMCs) are determined, ranging from 3 to 30 mg L−1. Non-ionic poly(propylen…
Acid-Labile Surfactants Based on Poly(ethylene glycol), Carbon Dioxide and Propylene Oxide: Miniemulsion Polymerization and Degradation Studies
2017
Partially degradable, nonionic AB and ABA type di- and triblock copolymers based on poly(propylene carbonate) and poly(ethylene glycol) blocks were synthesized via immortal copolymerization of carbon dioxide and propylene oxide, using mPEG or PEG as a macroinitiator, and (R,R)-(salcy)-CoOBzF5 as a catalyst in a solvent-free one-pot procedure. The amphiphilic surfactants were prepared with molecular weights (Mn) between 2800 and 10,000 g·mol−1 with narrow molecular weight distributions (1.03–1.09). The copolymers were characterized using 1H-, 13C- and DOSY-NMR spectroscopy and size exclusion chromatography (SEC). Surface-active properties were determined by surface tension measurements (crit…