Showing papers on "Tetrahydrofuran published in 2008"
TL;DR: In this article, phase equilibrium (pressure-temperature) measurements and Raman spectroscopic analyses for two mole fractions, 0.018 and 0.034, of tetra-n-butyl ammonium fluoride aqueous solutions were performed.
113 citations
TL;DR: The molecular aggregation of the pi-conjugated polymers, oligomers, and their binary blends can be controlled via suitable bulky substitution to tune their emission properties in solution as well as in the solid state.
Abstract: The role of pi-stack induced molecular aggregation on solution and solid-state luminescent properties was investigated for the tricyclodecane substituted bulky (p-phenylenevinylene)s (BTCD-60, with 60% bulky group), oligophenylenevinylenes (MEH-OPV and BTCD-OPV)s, and their polymer-oligomer binary blends. The natures of the solvent, concentration, solvent combinations (good or bad), and temperature were employed as stimuli to probe the origin of the molecular aggregates in bulky conducting polymers. Absorption, photoluminescence (PL), and time-resolved fluorescence spectroscopic techniques were employed as tools to trace aggregation in solvents such as toluene, tetrahydrofuran (THF), THF and methanol, or THF and water as well as in the solid state. The absorbance spectra of poly(2-methoxy-5-(2-ethylhexyloxy))-1,4-phenylenevinylene (MEH-PPV) and BTCD-60 indicated that the films obtained from polymers that were dissolved in aromatic solvents such as toluene were found to possess more pi-stacking as compared to that of films obtained from a good solvent such as THF. The solid-state emission spectrum of BTCD-60 was found to show almost a 5-6 times enhancement in PL intensity as compared to that of MEH-PPV. Concentration dependent excitation spectra of the polymers confirmed the presence of aggregated polymer chains in MEH-PPV, which is the main reason for the quenching of luminescence intensity in the polymer. Solvent induced aggregation studies of polymers in THF and methanol mixture further supports the existence of strong aggregation in MEH-PPV as compared to that of bulky BTCD-60. Variable temperature absorption studies confirmed the reversibility of molecular aggregation on heating/cooling cycles, and the extent of aggregation was found more in MEH-PPV chains as compared to that of BTCD-60. MEH-PPV/OPV binary blends were prepared in the entire composition range from 0 to 100% via solution blending techniques. Through selective PL excitation techniques, the effect of oligomer-to-polymer energy transfer and also luminescent enhancement in MEH-PPV via interchain separation were investigated. Both the energy transfer and the interchain separation were found to be more effective on the enhancement of luminescence properties in the BTCD blends as compared to that of MEH blends. Time-resolved fluorescence studies confirmed the existence of two types of species corresponding to the free and aggregated chains in the polymer matrix with lifetimes in the range of 0.5-2.0 ns. In the present investigation, we have successfully shown that the molecular aggregation of the pi-conjugated polymers, oligomers, and their binary blends can be controlled via suitable bulky substitution to tune their emission properties in solution as well as in the solid state.
104 citations
TL;DR: A series of new polyimides (PIs) containing tert-butyl side groups were synthesized via a polycondensation of 1,4-bis(4-aminophenoxy)-2,6-di-tert -butylbenzene (4) with various aromatic tetracarboxylic dianhydrides as mentioned in this paper.
Abstract: A series of new polyimides (PIs) containing tert-butyl side groups were synthesized via a polycondensation of 1,4-bis(4-aminophenoxy)-2,6-di-tert-butylbenzene (4) with various aromatic tetracarboxylic dianhydrides. The introduction of the asymmetric di-tert-butyl groups is an effective way to increase the interchain distance and decrease in the intermolecular force and packing ability of the resulting polymers. Thus, this novel PIs exhibit a low dielectric constant (2.74−2.92), low moisture absorption (0.32−1.53%), excellent solubility, and high glass transition temperature (276−398 °C). The PIs derived from the very rigid pyromellitic dianhydride (PMDA) were soluble in N-methyl-2-pyrrolidone, N,N-dimethylacetamide, chloroform, tetrahydrofuran, and cyclohexanone. The crystal structure of 1,4-bis(4-phthalimidophenoxy)-2,5-di-tert-butylbenzene indicates that the symmetric compound leads to the strong intermolecular interaction and good packing ability. In the 1H spectrum of the diamine 4, the protons of 4-a...
95 citations
TL;DR: The Sonogashira alkynylation of acid chlorides can be efficiently conducted in less than an hour by performing the reaction in tetrahydrofuran as a solvent and in the presence of one stoichiometrically necessary equivalent of triethylamine as a base.
Abstract: The Sonogashira alkynylation of acid chlorides can be efficiently conducted in less than an hour by performing the reaction in tetrahydrofuran as a solvent and in the presence of one stoichiometrically necessary equivalent of triethylamine as a base. This approach also opens new avenues for consecutive one-pot multicomponent reactions. As an example, the one-pot three-component pyrimidine synthesis illustrates the versatility of this modified Sonogashira protocol as an entry to diversity-oriented heterocycle synthesis in a one-pot fashion. The protocol can be completed within a few hours.
95 citations
TL;DR: A new diamine monomer containing heterocyclic pyridine and triphenylamine groups was synthesized by Chichibabin and nucleophilic fluoro-displacement reactions as discussed by the authors.
95 citations
TL;DR: While there was a decrease in quantum yield associated with ligand exchange and transfer to polar solvents, as is commonly found for colloidal quantum dots, the quantum yields determined were impressively high and decreased over time as the solutions were allowed to age in the presence of air.
Abstract: Hydrophobic lead sulfide quantum dots (PbS/OA) synthesized in the presence of oleic acid were transferred from nonpolar organic solvents to polar solvents such as alcohols and water by a simple ligand exchange with poly(acrylic acid) (PAA). Ligand exchange took place rapidly at room temperature When a colloidal solution of PbS/OA in tetrahydrofuran (THF) was treated with excess PAA, the PbS/PAA nanocrystals that formed were insoluble in hexane and toluene but could be dissolved in methanol or water, where they formed colloidal solutions that were stable for months. Ligand exchange was accompanied by a small blue shift in the band-edge absorption, consistent with a small reduction in particle size. While there was a decrease in quantum yield associated with ligand exchange and transfer to polar solvents, as is commonly found for colloidal quantum dots, the quantum yields determined were impressively high: PbS/OA in toluene (82%) and in THF (58%); PbS/PAA in THF (42%) and in water (24%). The quantum yields ...
93 citations
TL;DR: The accuracy of the methodology for two solvents of differing polarity indicates that this technique is suitable to study CN probes in proteins.
Abstract: The C≡N bond is a powerful probe of protein structure and dynamics because it absorbs in a region of the infrared spectrum apart from the other vibrations that occur naturally in proteins, and because its infrared absorption line shape is sensitive to specific characteristics of the local environment. Since the polarity experienced by the probe can differ dramatically within the protein, infrared spectroscopy of a C≡N site-specifically labeled residue can be used to infer its local environment within the protein. It has been shown experimentally that the spectrum of acetonitrile in water is different in terms of peak position and width compared to acetonitrile in tetrahydrofuran (THF). An optimized quantum mechanics/molecular mechanics method for calculating accurate vibrational frequencies in condensed-phase was parametrized for acetonitrile in water. The transferability of the methodology to a different solvent was tested by computing the infrared line shapes of acetonitrile in both water and THF and co...
90 citations
TL;DR: In this paper, high pressure vapor-liquid phase equilibrium data for the binary mixtures of organic solvent (ethanol, tetrahydrofuran, o-xylene, m -xylene) with CO 2 have been measured at temperatures between 313.2 and 333.2 K and pressures from 1 to 14 MPa using a static analytic method.
Abstract: High pressure vapor–liquid phase equilibrium data ( P – T – x – y ) for the binary mixtures of organic solvent (ethanol, tetrahydrofuran, o -xylene, m -xylene, p -xylene) with CO 2 have been measured at temperatures 313.2, 333.2, 353.2 K and pressures from 1 to 14 MPa using a static-analytic method. For the systems ethanol–CO 2 and tetrahydrofuran–CO 2 , the experimental data at 313.2 and 333.2 K are in a good agreement with literature data. The experimental results have been correlated by the Peng–Robinson equation of state in combination with van der Waals one fluid mixing rule with two adjustable parameters.
87 citations
TL;DR: In this paper, the effect of the interactions between polyvinylidene fluoride (PVDF) chains and solvent molecules on the structure and crystallization behavior of PVDF in films obtained by solution casting was investigated.
Abstract: The present work focused on the effect of the interactions between poly(vinylidene fluoride) (PVDF) chains and solvent molecules on the structure and crystallization behavior of PVDF in films obtained by solution casting. In a single solvent system, the film cast from the good solvent of N,N‐dimethylformamide (DMF), showed dominantly β‐phase crystals with the highest PVDF crystallinity (50.6%) and the largest spherulite size, about 4 μm, at the top surface. The samples deposited from good swelling agents, such as tetrahydrofuran (THF) and methyl ethyl ketone (MEK), exhibited mainly the original α phase with some amount of β‐phase crystals; the crystallization behavior and the morphology of the surface were similar to the original PVDF resin, because of the only partially dissolved PVDF chains in these two solvents. In a mixed solvent system (THF/DMF), the β phase formation linearly increased as the DMF component increased, determined by Fourier transform infrared spectroscopy (FTIR) techniques, owing to i...
79 citations
TL;DR: In this paper, Chenfu coal (SFC), its liquefaction residue (RL), and carbon disulfide (CS{sub 2})/tetrahydrofuran (THF)-inextractable matter (RE) were subject to ruthenium ion-catalyzed oxidation to understand the differences in structural features among the above three samples.
Abstract: Shenfu coal (SFC), its liquefaction residue (RL), and carbon disulfide (CS{sub 2})/tetrahydrofuran (THF)-inextractable matter (RE) were subject to ruthenium ion-catalyzed oxidation to understand the differences in structural features among the above three samples. The results suggest that SFC is rich in long-chain arylalkanes and {alpha}. {omega}-diarylalkanes (DAAs) with carbon number of methylene linkage from 2 to 4 and that long-chain arylalkanes and DAAs are reactive toward hydroliquefaction and soluble in a CS{sub 2}/THF mixed solvent, whereas highly condensed aromatic species in SFC show poor solubility in the CS{sub 2}/THF mixed solvent. 29 refs., 6 figs., 4 tabs.
77 citations
TL;DR: Partitioned dispersive liquid-liquid microextraction efficiency was demonstrated for the extraction of polar organic compounds (chlorophenoxyacetic acids) prior to high performance liquid chromatography (HPLC).
TL;DR: Ma et al. as mentioned in this paper proposed a method to achieve the b phase of polyvinylidene fluoride (PVDF) by crystallizing from a swelling agent/solvent mixture.
Abstract: Poly(vinylidene fluoride) (PVDF) is one of the semicrystalline polymers with at least four crystalline forms referred to as a, b, c, and d phase, among which the b phase has gained substantial importance due to its advantageous pyroand piezo-electric properties [1, 2]. It requires a better method to induce the formation of b phase crystal in order to improve the electrical properties of PVDF. b phase is not usually obtained by crystallization from the melt, but it is normally obtained by various methods including tensile deformation and uniaxial compressional deformation of a phase [3, 4], blending with small contents of poly(methyl methacrylate) (PMMA) [5, 6] or poly(o-methoxyaniline) (POMA) [7], quenching and then annealing process [8], applying a strong electric field [9] and crystallizing from solution at appropriate conditions [10–12]. In all these methods which used to prepare b phase of PVDF, the one grown from a single solvent is widely used because of its facility and controllability. However, few literatures are concentrated on the solvent-induced b phase formation in the mixed solvent. In this letter a novel method to achieve the b phase of PVDF is carried out by crystallizing from swelling agent/solvent mixture. Dissolution of a semicrystalline polymer, such as PVDF, requires disruption of strong interchain forces in order regions. So the rate of polymer dissolution is dependent on the type of liquid [13]. It has been reported that tetrahydrofuran (THF) is a good swelling agent at 60 C for PVDF; N, N-dimethylformamide (DMF) is a solvent for it at 20 C [13]. The aim of this study is to include the effects of the THF/ DMF mixture with various mass ratios of each component on the crystalline phase formation and crystallization behavior in the PVDF film by solution casting. It was characterized by Fourier transform infrared (FTIR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and scanning electron microscope (SEM) techniques. The PVDF (Kynar K-761, Mw = 441000) utilized in this work was supplied by Elf Atochem of North America Inc. (USA). PVDF resin was dissolved in the THF/ DMF mixture with different mass ratio (m/m composition of THF/DMF = 9:1, 8:2, and 5:5) at 50 C. The solubility of the PVDF was improved by an increase of DMF content in the mixture of solvents because of the reinforced disruption of the intermolecular polymer bonds (via interaction of the C = O dipole with the CH2CF2 dipole or by limited hydrogen bonding) [14, 15]. Films (thickness: *50 lm) of PVDF were quiescently cast from each solution with 10 wt% PVDF (initial polymer concentration) at 50 C, and the glass substrate was used for solution casting. After the solvents evaporated the films were peeled off from the glass substrate at room temperature. The residue of DMF and THF was allowed to evaporate in an air oven for about 1 week at room temperature. FTIR spectra of films were obtained on a FTIR spectrometer (Bruker Vector-22). WAXD was done in a Shimadzu XRD-6000 diffractometer (Cu Ka radiation, 40 kV and 30 mA) at a scanning velocity of 4 /min. The melting behavior of the films was measured with a Perkin– Elmer DSC-7C differential scanning calorimeter using a heating rate of 10 C/min. SEM micrographs were taken on a Jeol JSM-5900 microscope. W. Ma J. Zhang (&) College of Materials Science and Engineering, Nanjing University of Technology, No.5, Xin Mo Fan Road, Nanjing 210009, P.R. China e-mail: zhangjun@njut.edu.cn
TL;DR: In this article, a series of highly fluorescent liquid-crystalline perylenebisimide molecules having amide or ester linkage and end-capped by phenyl, monodecyloxy phenyl or tridodeecylox phenyl units have been synthesized and fully characterized.
Abstract: A series of highly fluorescent liquid-crystalline perylenebisimide molecules having amide or ester linkage and end-capped by phenyl, monododecyloxy phenyl, or tridodecyloxy phenyl units have been synthesized and fully characterized. The amide-functionalized series self-organized to form H type aggregates regardless of their end-capping in organic solvents like tetrahydrofuran (THF), toluene, and dichloromethane. On the other hand, only the monododecyloxy phenyl end-capped molecule in the ester series showed a tendency to self-organize with a typical J type aggregation in toluene. In both series, the highest aggregation tendency was shown by the one having monododecyloxy phenyl end-capping, with the transition temperature from aggregated to molecularly dissolved species occurring at 60 °C for the amide and 50 °C for the ester molecule. At higher concentrations in toluene, the fluorescence spectra of the monododecyloxy phenyl and tridodecyloxy phenyl terminal-substituted amide derivatives showed the formati...
TL;DR: The solubility of l-(+)-ascorbic acid in water, ethanol, methanol, propan-2-ol, acetone, acetonitrile, ethyl acetate, and tetrahydrofuran was measured by a gravimetrical method from (293 to 323) K as mentioned in this paper.
Abstract: The solubility of l-(+)-ascorbic acid in water, ethanol, methanol, propan-2-ol, acetone, acetonitrile, ethyl acetate, and tetrahydrofuran was measured by a gravimetrical method from (293 to 323) K, and the solubility data were correlated against temperature. The solubility of l-(+)-ascorbic acid in water and methanol was high compared with other solvents.
TL;DR: In this article, a vanadium-III complex with salicylaldiminato ligands was obtained by treating with 1.0 equiv of (RN═CH)ArOH in tetrahydrofuran (THF) in the presence of excess triethylamine (TEA).
TL;DR: In this paper, the storage capacity of tetrahydrofuran hydrate was investigated by means of pressure-volume-temperature (p-V-T ) measurement and Raman spectroscopic analysis.
TL;DR: Cryogenic transmission electron microscopy suggests that, as the poly(ethylethylene) block transitions from the core to the corona, the micelle morphologies evolve from disks to oblate ellipsoid micelles (with some vesicles), with worms and spheres evident at intermediate compositions.
Abstract: Miktoarm star triblock copolymers μ-[poly(ethylethylene)][poly(ethylene oxide)][poly(perfluoropropylene oxide)] self-assemble in dilute aqueous solution to give multicompartment micelles with the cores consisting of discrete poly(ethylethylene) and poly(perfluoropropylene oxide) domains. Tetrahydrofuran is a selective solvent for both the poly(ethylethylene) and poly(ethylene oxide) blocks, and thus in tetrahydrofuran mixed corona micelles are favored with poly(perfluoropropylene oxide) cores. The introduction of tetrahydrofuran into water induces an evolution from multicompartment micelles to mixed corona [poly(ethylethylene) + poly(ethylene oxide)] micelles, as verified by dynamic light scattering and nuclear magnetic resonance spectroscopy. A mixed solvent containing 60 wt % tetrahydrofuran corresponds to the transition point, as verified by analysis of a poly(ethylethylene)-poly(ethylene oxide) diblock copolymer in the same solvent mixtures. Furthermore, cryogenic transmission electron microscopy sugg...
TL;DR: A gas sensor developed by using the chemiluminescence (CL) emission from the oxidation of ethyl ether by oxygen in the air on the surface of borate glass is a simple, sensitive and selective gas sensor for the determination of trace ethyl Ether.
Abstract: A gas sensor was developed by using the chemiluminescence (CL) emission from the oxidation of ethyl ether by oxygen in the air on the surface of borate glass. Theoretical calculation, together with experimental investigation, revealed the main CL reactions: ethyl ether is first oxidized to acetaldehyde and then to acetic acid, during which main luminous intermediates such as CH3CO• are generated and emit light with a peak at 493 nm. At a reaction temperature of 245 °C, the overall maximal emission was found at around 460 nm, and the linear range of the CL intensity versus the concentration of ethyl ether was 0.12−51.7 μg mL−1 (R = 0.999, n = 7) with a limit of detection (3σ) of 0.04 μg mL−1. Interference from foreign substances including alcohol (methanol, ethanol and isopropanol), acetone, ethyl acetate, n-hexane, cyclohexane, dichloromethane, or ether (n-butyl ether, tetrahydrofuran, propylene oxide, isopropyl ether and methyl tert-butyl ether) was not significant except a minimal signal from n-butyl et...
TL;DR: In this paper, a series of size-controlled cyclic poly(tetrahydrofuran)s (M n,NMR of 4400-8 600) that consist exclusively of the monomer, i.e., oxytetramethylene, unit (I) have been prepared in high yield through the metathesis polymer cyclization of a telechelic precursor having allyl groups, 1, in the presence of a Grubbs catalyst, and the subsequent hydrogenation of the linking unit in the Adams' catalyst (PtO 2 ).
Abstract: A series of size-controlled, cyclic poly(tetrahydrofuran)s (M n,NMR of 4400-8 600) that consist exclusively of the monomer, i.e., oxytetramethylene, unit (I) have been prepared in high yield through the metathesis polymer cyclization of a telechelic precursor having allyl groups, 1, in the presence of a Grubbs catalyst, and the subsequent hydrogenation of the linking, i.e., 2-butenoxy, unit in the presence of an Adams' catalyst (PtO 2 ). A remarkable topology effect has subsequently been observed upon the isothermal crystallization of these two model polymers, showing distinctive spherulite growth rates and spherulite morphologies in comparison with the relevant linear poly(tetrahydrofuran) counterpart that has ethoxy end groups (II).
01 Jan 2008
TL;DR: In this paper, the statistics of liquid-to-crystal nucleation are measured for clathrate-forming mixtures of tetrahydrofuran (THF) and water using an automatic lag time apparatus (ALTA).
Abstract: The statistics of liquid-to-crystal nucleation are measured for clathrate-forming mixtures of tetrahydrofuran (THF) and water using an automatic lag time apparatus (ALTA). We measure the nucleation temperature using this new apparatus in which a single sample is repeatedly cooled, nucleated and thawed. This is done for a series of tetrahydrofuran concentrations and in several different sample tubes since the nucleation is heterogeneous and so occurring on the tube wall. The measurements are also done at the same concentrations and tubes but with an added catalyst, a single crystal of silver iodide.
TL;DR: In this article, a detailed analysis of the degradation products generated during storage of poly(methyl methacrylate) (pMMA) and polystyrene (pSty) carrying cumyldithiobenzoate (CDB) endgroups is presented.
Abstract: We report on the detailed mass spectrometric analysis of the degradation products generated during storage of poly(methyl methacrylate) (pMMA) and polystyrene (pSty) carrying cumyldithiobenzoate (CDB) endgroups. Samples were stored in either a cyclic ether (tetrahydrofuran) (THF) or an inert solvent (dichloromethane). The degradation process was followed over a period of 4-weeks. Degradation rate of the reversible addition fragmentation (RAFT) polymer strongly depends on the hydroperoxide-content of the solvent. Mass spectrometric evidence supports an unexpected radical degradation mechanism for the pMMA macroRAFT agent. Hydroperoxide functional pMMA was the single product after less than 7 days in high purity THF. No formation of the sulfine/thioester was observed. The identity of the hydroperoxide was unambiguously assigned using accurate mass measurements by Fourier-Transform ion-cyclotron-resonance mass spectrometry together with chemical identification reactions. The hydroperoxide end group formation proceeds efficiently as well as in high yields and thus constitutes a powerful method for end group modification. The degradation pathways of the CDB functional pSty in THF include mainly oxidation towards the sulfine/thioester, with little degradation via thermal elimination of dithiobenzoic acid and subsequent epoxidation. The shelf life of CDB functional polymers is limited even in inert solvent because of this inherent but slow thermal elimination reaction. Because of the short period necessary for the transformation of the functional dithiobenzyl endgroups, substitution of cyclic ethers as solvents for RAFT polymers in synthesis and analysis is strongly suggested. © 2008 Wiley Periodicals, Inc.
TL;DR: It is shown for the first time that it is possible to stabilize structure sH of hydrogen clathrate hydrate with the help of some selected promoters with an estimated hydrogen storage capacity as high as 1.4 wt % of H2.
Abstract: In this experimental phase equilibrium study, we show for the first time that it is possible to stabilize structure sH of hydrogen clathrate hydrate with the help of some selected promoters. It was established that the formation pressures of these systems are significantly higher than that of structure sII of hydrogen clathrate hydrate when tetrahydrofuran (THF) is used as a promoter. Although no experimental evidence is available yet, it is estimated that the hydrogen storage capacity of structure sH can be as high as 1.4 wt % of H2, which is about 40% higher compared to the hydrogen storage capacity in structure sII.
TL;DR: In this article, a hydrogen delocalization model and a proposed hydrogen hydrate phase diffusion (HHPD) model were used to analyze the formation mechanisms of H2-THF clathrate hydrate.
Abstract: Binary H2-THF clathrate hydrate formation kinetics were investigated with a pressure decay method at temperatures from 266.7 to 275.1 K, at initial pressures from 3.6 to 8.4 MPa, and at stoichiometric THF hydrate concentrations for particle sizes between 212 and 1,400 μm. Formation rate increased for smaller particle sizes, higher pressures and lower-temperatures. A hydrogen delocalization model and a proposed hydrogen hydrate phase diffusion (HHPD) model were used to analyze the formation mechanisms. The HHPD model assumes that the H2-THF hydrate phase is formed due to hydrogen adsorption onto the particle surface that is followed by subsequent diffusion of hydrogen into the clathrate hydrate. The HHPD model could express the kinetics quantitatively at the experimental conditions studied. Values of the hydrogen diffusion coefficient in the clathrate hydrate estimated from the bulk data and the phase thickness in the HHPD model agreed well with the literature. © 2008 American Institute of Chemical Engineers AIChE J, 2008
TL;DR: In this article, the synthesis and characteristic properties of polymers P-1−P-3 are described containing the 2,3,5,6-tetraarylated pyrrolo[3,4-c]pyrrole-1, 4-dione unit in the main chain.
Abstract: Synthesis and characteristic properties of polymers P-1−P-3 are described containing the 2,3,5,6-tetraarylated pyrrolo[3,4-c]pyrrole-1,4-dione unit in the main chain. P-1 is prepared from 2,5-bis(4-t-butylphenyl)-3,6-bis(4′-bromophenyl)pyrrolo[3,4-c]pyrrole-1,4-dione (DPP1) and 9,9-di-n-hexylfluorene-2,7′-bispinacolato-boronester 3, P-2 from 2,5-bis(4′-bromo-phenyl)-3,6-bis(4-t-butylphenyl)-pyrrolo[3,4-c]pyrrole-1,4-dione (DPP2) and 3, and P-3 from DPP1, 3, and 2,5-bis(n-hexyloxybenzene)-1,4-bispinacolatoboronester 4 via Pd-catalyzed Suzuki coupling. Molecular weights of the polymers are about 8000−10 000 Da. All polymers are soluble in common organic solvents such as toluene, chloroform, dichloromethane, tetrahydrofuran (THF), and dimethyl sulfoxide (DMSO) and exhibit a strong fluorescence with Stokes shift up to 56 nm (P-3) and quantum yield up to 81% (P-1). Although P-1 and P-2 are isomers, their optical and electrochemical properties are very different. P-1 with a polyconjugated carbon backbone exhibi...
TL;DR: In this paper, charged nanofiltration membranes were prepared by blending polysulfone (PSf) with the polyelectrolyte sulfonated poly(ether ether ketone) (SPEEK).
TL;DR: Solution phase NMR spectroscopic characterization of the tris(N-2',6'-diisopropylphenyl(naphthyl)amidate)yttrium mono(tetrahydrofuran) complex showed a highly symmetric species, consistent with a fluxional coordination environment for these compounds.
Abstract: The direct synthesis of yttrium amidate complexes using the simple reaction of amide proligands and Y(N(SiMe3)2)3 results in the high-yielding preparation and isolation of crystalline, monomeric materials. The complex, tris(N-2′,6′-diisopropylphenyl(naphthyl)amidate)yttrium mono(tetrahydrofuran) (4), was structurally determined to be a 7-coordinate C1 symmetric structure, maintaining one bound tetrahydrofuran molecule. Compound 4 (C12H17[NCO]C10H7)3Y(C4H8O) crystallized in the monoclinic space group P2(1)/c with a = 13.7820(11) A, b = 33.598(3) A, c = 16.0575(12) A, α = 90°, β = 98.762(3)°, γ = 90°, Z = 4. Solution phase NMR spectroscopic characterization of this same complex showed a highly symmetric species, consistent with a fluxional coordination environment for these compounds. Preliminary studies into the initiation of e-caprolactone ring-opening polymerization using these complexes indicate high activity, producing high molecular weight polymer.
TL;DR: Polyaniline, a polymer widely known to be poorly soluble in a wide range of solvents has been successfully fabricated into an asymmetric membrane and stabilised by thermally induced cross-linking to result in a THF stable pervaporation membrane tested over 40h as mentioned in this paper.
TL;DR: In this article, a mixture of poly(crown ether)s (2−5) as a trunk polymer and dumbbell-shaped bifunctional secondary ammonium salt 6 bearing a disulfide linkage and bulky end caps as a cross-linking agent was synthesized in the presence of a catalytic amount of benzenethiol via a reversible thiol−disulfide interchange reaction.
Abstract: Polyrotaxane networks were synthesized from a mixture of poly(crown ether)s (2−5) as a trunk polymer and dumbbell-shaped bifunctional secondary ammonium salt 6 bearing a disulfide linkage and bulky end caps as a cross-linking agent in the presence of a catalytic amount of benzenethiol via a reversible thiol−disulfide interchange reaction. Trunk polymers 2−4 were prepared by copolymerization of bis(hydroxymethyl)dibenzo-24-crown-8-ether 1 and comonomers. Poly(crown ether) 5 bearing a poly(tetrahydrofuran) (PTHF) spacer was also synthesized from 1 and PTHF with 4,4′-methylenebis(phenyl isocyanate) (MDI) in N,N-dimethylacetamide (DMAc) at room temperature. The treatment of these poly(crown ether)s (2−5) with axle component 6 in the presence of benzenethiol gave the corresponding polyrotaxane networks (7−10) in quantitative yields. We confirmed the cross-linking process by monitoring the 1H NMR spectral change during the polymerization. Thermal properties, swelling, and dynamic viscoelasticity of these polyro...
TL;DR: An efficient three-step route for the synthesis of N-1 alkyl/aryl-substituted hydantoins was developed from inexpensive commercially available substrates in this paper.
TL;DR: The results obtained showed that tetrahydrofuran at over the range of selected concentrations could completely inhibit dehydrogenase activity during period of incubation, in the contrary, not to the protease activity, and strongly affected the phosphatase, urease and catalase activities which declined with increasing of tetrahytochemical concentration.