Search results for "Oxide"
showing 10 items of 6424 documents
Well-Defined Multi-Amino-Functional and Stimuli-Responsive Poly(propylene oxide) by Crown Ether Assisted Anionic Ring-Opening Polymerization
2017
Multi-amino-functional poly(propylene oxide) (PPO) copolymers were synthesized by the anionic ring-opening copolymerization (AROP) of N,N-diethyl glycidyl amine (DEGA) and propylene oxide (PO). A solvent free synthesis route using potassium counterions and crown ether for the AROP enabled controlled (co)polymerization with full conversion. The strategy provided access to PPO-b-PDEGA block copolymers, statistical PPO-co-PDEGA copolymers, and, for the first time, PDEGA homopolymer. Molecular weights in the range of 1400 to 4200 g/mol (Mn) and dispersities (Mw/Mn) below 1.1 were obtained. Both the kinetics and resulting microstructure of the statistical copolymerization were investigated by in…
Consequences of linking charged and uncharged monomers to binary copolymers studied in dilute solution. Part II: Non-additivity effects in the viscom…
2017
Abstract Copolymers of ethylene oxide (EO) and N,N-dimethyl aminoethyl methacrylate (R) or [2-(methacryloyloxy)ethyl] trimethylammonium iodide (R+) were studied in dilute solution: P ( EO p – b – R n ) ( I ) , P(Rn(1−f) – ran – R+n f) ( II ) , and P ( EO p – b – R n + ) ( III ) ; n and p give the numbers of monomers and f is the degree of charging. For II (variable f) and III (variable n) the effects of charging on the intrinsic viscosities [η] are well described by Boltzmann sigmoids. The deviation of [ η ] from [ η ] add (calculated from the corresponding homopolymer data, assuming additivity of the individual contributions) are quantified by σ = [ η ] / [ η ] add - 1 measuring the segreg…
Complexation of phosphine ligands with peracetylated β-cyclodextrin in supercritical carbon dioxide: Effect of temperature and cosolvent on the equil…
2009
Abstract The interaction between peracetylated-β-cyclodextrin and tert-butyl and adamantyl functionalized triphenylphosphine derivatives was studied in supercritical carbon dioxide (scCO 2 ) based solvent media by UV–vis spectroscopy. The equilibrium constant for a 1:1 complexation reaction was obtained from titration spectra both in pure carbon dioxide and in the presence of methanol as a cosolvent in the temperature range 308–323 K to estimate the internal energy and entropy of the inclusion equilibrium. The values of the equilibrium constants were found significantly smaller than those obtained in aqueous solution with analogous phosphines and substantially independent of the nature of t…
Membrane Transport of l-Arginine and Cationic Amino Acid Analogs
2000
Publisher Summary This chapter reviews the current knowledge of the mechanisms and regulation of cationic amino acids (CAA) carrier proteins and discusses the potential involvement of each transporter in supplying L-arginine for nitric oxide biosynthesis. The CAA L-arginine, the substrate for nitric oxide synthases (NOSs), is considered a semi-essential amino acid in most mammals. Consequently, mammalian cells must be capable of exchanging CAA with the environment. The bilayer of the plasma membrane is impermeable to polar molecules, and thus, specialized carrier proteins with distinct substrate specificity transport hydrophilic solutes such as amino acids. L-arginine shares the same transp…
Selective Surface Modification of SiO2−TiO2 Supports with Phosphonic Acids
2004
The selective surface modification by phosphonic acids of SiO2−TiO2 supports at the micrometer and molecular scale was investigated. Under aqueous conditions, phosphonic acids bind to TiO2 and not to SiO2 surfaces. A micropatterned support was prepared by electron beam microlithography and selectivity, of the surface modification was evidenced using scanning Auger electron spectroscopy (SAES). The second support was a mesoporous SiO2−TiO2 mixed oxide (10 mol % Ti) epoxidation catalyst prepared by sol−gel processing. Selectivity was deduced from the decrease of the catalytic activity upon modification and from chemical analysis; bonding modes to the surface were investigated using solid-stat…
Low-Temperature Optical Spectroscopy of Native and Azide-Reacted Bovine Cu,Zn Superoxide Dismutase. A Structural Dynamics Study
1994
The optical absorption spectra of native and N(3-)-reacted Cu,Zn superoxide dismutase (SOD) has been studied in the temperature range 300-10 K. The broad d-d bands observed in the room temperature spectrum, centered at 14,700 cm-1 (native enzyme) and at 15,550 cm-1 (N(3-)-reacted enzyme), are clearly split at low temperature into two bands each, centered at 12,835 and 14,844 cm-1 and at 14,418 and 16,300 cm-1, respectively. The thermal behavior of the 23,720 cm-1 band present in the spectrum of the native enzyme indicates that this band belongs to the His61-->Cu(II) ligand to metal charge transfer transition. Analysis of the zeroth, first, and second moments of the various bands as a functi…
The influence of aromatic cations on the geometries of the Bi(III) halide polyhedra. Synthesis and crystal structures of quinolinium, isoquinolinium …
2001
Abstract The compounds [quinolinium]4[Bi2Cl10] (1), [isoquinolinium]4[Bi2Cl10].2H2O (2) and [8-hydroxyquinolinium]4[BiCl6]·Cl·2H2O (3) have been obtained by reacting bismuthate oxide and the appropriate base in HCl acid medium. The crystal structures of 1 and 2 consist of quinolinium and isoquinolinium cations, respectively, interacting through hydrogen bonding with [Bi2Cl10]4− dimers. The different degree of interactions in the two derivatives causes significant differences in the bond distances of the anions. The crystal structure of 3 is made of [BiCl6]3− and Cl− anions and 8-hydroxyquinolinium cations. Hydrogen bond interactions including the N-bonded and O-bonded H atoms together with …
From Biocompatible to Biodegradable: Poly(Ethylene Glycol)s with Predetermined Breaking Points
2013
Poly(ethylene glycol) (PEG) is the gold standard polymer for biomedical applications. PEG is known for its biocompatibility and antifouling properties and is widely used for bioconjugation. However, like other synthetic polymers in the field, PEG is not biodegradable, limiting its use for parenteral formulations and protein conjugation to a molecular weight range with a specific upper limit (commonly 40–60 kDa) to avoid polyether accumulation in human tissue. For these biomedical applications, but also for other purposes such as cleavable hydrogels and templates for porous membranes, several routes for the insertion of in-chain biocleavable moieties, such as acetals or disulfides, into PEG …
Inverted Solution Processable OLEDs Using a Metal Oxide as an Electron Injection Contact.
2007
A new type of bottom-emission electroluminescent device is described in which a metal oxide is used as the electron-injecting contact. The preparation of such a device is simple. It consists of the deposition of a thin layer of a metal oxide on top of an indium tin oxide covered glass substrate, followed by the solution processing of the light-emitting layer and subsequently the deposition of a high-workfunction (air-stable) metal anode. This architecture allows for a low-cost electroluminescent device because no rigorous encapsulation is required. Electroluminescence with a high brightness reaching 5700 cd m–2 is observed at voltages as low as 8 V, demonstrating the potential of this new a…
Synthesis of cyanoacetic acid by carbon dioxide and electrogenerated acetonitrile anion in undivided cells equipped with sacrificial anodes
2008
The electrochemical synthesis of cyanoacetic acid was performed by cathodic reduction of tetraalkylammonium salts (R4NX) in acetonitrile in undivided cells equipped with sacrificial anodes with concomitant or subsequent addition of carbon dioxide. These syntheses avoid the use of dangerous reagents, yield cyanoacetic acid in moderate faradic yields and confirm that the cathodic reduction of tetraalkylammonium salts in the presence of acetonitrile leads to the formation of the anion CNCH2-.