Mixture Of Dimethylformamide Research Articles

Effects of polyvinylpyrrolidone on carbothermal reduction and nitridation of titanium nitride powder

Titanium nitride powders were synthesised via carbothermal reduction and nitridation of TiO2 non-hydrolytic gels using polyvinylpyrrolidone as the carbon source. Compared with solid carbon black as carbon resource, polyvinylpyrrolidone was dissolved in a mixture of absolute alcohol, titanium tetrachloride and dimethylformamide and can fully contact with the titanium source in the liquid–liquid mixture, which will contribute to increase the reaction and conversion rates of titanium nitride. The optimum parameters for polyvinylpyrrolidone molecular weight and C/Ti molar ratio were 1 300 000 and 12:1, respectively. The average grain size of Titanium nitride powders was 100 nm.

BaTiO3–CoFe2O4–BaTiO3 trilayer composite thin films prepared by chemical solution deposition

Multiferroic BaTiO3–CoFe2O4–BaTiO3 thin films were synthesized by spin coating of Co(NO3)2–Fe(NO3)3 and Ba(OAc)2–Ti(i-OPr)4 dissolved in a mixture of acetic acid and dimethylformamide. Stepwise thermal treatment at 200, 400 and 800°C led to the desired phases. The phase formation process was monitored by thermoanalytic, XRD, IR and Raman measurements. SEM was used to characterize the structure and thickness of each layer. Two samples with different thicknesses of perovskite and spinel layers are discussed. Sample 1 consists of 120nm CoFe2O4 between two 70nm BaTiO3 layers. For sample 2, the 90nm BaTiO3 top and bottom layers are enclosing 220nm CoFe2O4. The surface qualities were determined by AFM indicating rms roughness values of about 4nm. Magnetic investigations reveal slightly anisotropic behavior. Polarization measurements show hysteresis loops (PS(max)=29μCcm−2; PR(max)=17μCcm−2) with switching peaks at the corresponding coercive fields.

The structure of a coordination polymer constructed of manganese(II) biphenyl-4, 4′-dicarboxylate

AbstractManganese(II) biphenyl-4,4′-dicarboxylate, prepared by crystallization of a mixture of biphenyl-4,4′- dicarboxylic acid, manganese(II) chloride, and di(4-pyridyl)acetylene as base in a mixture of dimethylformamide, ethanol and water in a closed vessel at elevated temperatures forms a 3D network of {[Mn(bpdc)(H2O)2][Mn(bpdc)(H2O)]} containing one five-fold coordinated and one six-fold coordinated Mn metal center (X-ray structure determination). Scanning tunneling microscopic (STM) measurements of manganese biphenyl-4,4′-dicarboxylate adsorbed on highly oriented pyrolytic graphite showed strands, the averaged diameter of which amounts to 18±1 nm, whereas the apparent height is about 0.5±0.02 nm.

Process intensification on the separation of benzene and thiophene by extractive distillation

The separation of benzene and trace thiophene by extractive distillation was intensified in two aspects, that is, selection of a suitable entrainer and improvement of the process. The mixture of dimethylformamide (DMF) and an ionic liquid (IL) was chosen as the entrainer. Vapor–liquid equilibrium (VLE) experiments using pure DMF and a mixed entrainer were conducted, and UNIFAC model for ILs was extended to the benzene‐thiophene‐DMF‐IL system. The results demonstrated that volatilization loss of DMF in the vapor phase was significantly reduced by adding IL. Moreover, an improved process with only four columns using a mixed entrainer was proposed. The results indicated that the improved process is more promising for decreasing energy consumption and equipment investment compared with the conventional six‐column process. The total heat duties of reboilers and condensers was decreased by 6.47% and 6.41%, respectively. The process intensification strategy may be directly extended to separate trace components of other systems. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4470–4480, 2015

Facile synthesis of MoS2/RGO in dimethyl-formamide solvent as highly efficient catalyst for hydrogen evolution

MoS2/RGO nanocomposites as highly effective electrocatalysts for hydrogen evolution reaction (HER) have been synthesized by one-pot solvothermal route using dimethyl-formamide (DMF) as solvent. For comparison, MoS2/RGO has also been prepared in pure H2O and H2O–DMF mixture. The good dispersion of MoS2 nanoparticles on the surface of MoS2/RGO obtained in DMF can be seen from TEM and SEM images, which implying the more active sites for HER. The electrocatalytic measurements confirm that the obtained MoS2/RGO in DMF exhibits the smaller onset overpotential of 130mV and lower tafel slop of 42mVdec−1, which indicating the better electrocatalytic activity than MoS2/RGO in H2O or H2O–DMF mixture. It may be attributed to the better role of DMF on dispersing RGO and controlling the growth of MoS2. Therefore, DMF may be the more suitable solvent for preparing excellent electrocatalysts for HER than H2O.

Formation of uniform PVDF fibers under ultrasound exposure in presence of anionic surfactant

Polyvinylidene fluoride (PVDF) was electrospun into fibrous membranes from its solutions in mixture of dimethylformamide (DMF) and acetone with and without an anionic fluorosurfactant. The results indicate that PVDF fibers contain a number of beads at any solvents compositions and solution concentrations. Addition of the surfactant does not affect considerably the morphology of fibers, however it helps to decrease the surface tension of the solution and reduce the beading of fibers. The most important factor affecting the fiber morphology is sonication. Sonication of the spinning solution promotes the formation of perfect, uniform, thin and cylindrical PVDF nanofibers without any beading.

Separation of parent homopolymers from poly(ethylene oxide) and polystyrene-based block copolymers by liquid chromatography under limiting conditions of desorption – 1. Determination of the suitable molar mass range and optimization of chromatographic conditions

We studied molar mass limits for the LC LCD separation of parent polystyrene (PS) and poly(ethylene oxide) (PEO) homopolymers from PEO/PS based block copolymers and we identified optimized chromatographic conditions. Time delays between barriers and sample injections were 0–2–3′10. Eluent was composed of dimethylformamide (DMF) 40wt.% and 1-chlorobutane (CLB) 60wt.%; Barrier 1 (B1), which retained block copolymer, was composed of 100wt.% CLB and Barrier 2 (B2), which retained PEO, was a mixture of DMF and CLB, which proportions were adjusted to studied block copolymers. With B2 composed of DMF 23wt.% and CLB 77wt.%, we obtained successful separation of PS23K-b-PEO35K-b-PS23K (56.5wt.% of PS, the subscripts indicate the molar mass in kgmol−1 of each polymer part in the block copolymer) from its parent homopolymers. With B2 adjusted to DMF 30wt.% and CLB 70wt.%, PS2.3K-b-PEO3.1K (42.6wt.% of PS) was also efficiently separated from its parent homopolymers.

Tandem amine and ruthenium-catalyzed hydrogenation of CO2 to methanol.

This Communication describes the hydrogenation of carbon dioxide to methanol via tandem catalysis with dimethylamine and a homogeneous ruthenium complex. Unlike previous examples with homogeneous catalysts, this CO2-to-CH3OH process proceeds under basic reaction conditions. The dimethylamine is proposed to play a dual role in this system. It reacts directly with CO2 to produce dimethylammonium dimethylcarbamate, and it also intercepts the intermediate formic acid to generate dimethylformamide. With the appropriate selection of catalyst and reaction conditions, >95% conversion of CO2 was achieved to form a mixture of CH3OH and dimethylformamide.

Prediction of the Toxicity of Dimethylformamide, Methyl Ethyl Ketone, and Toluene Mixtures by QSAR Modeling

In this study, we analyzed the toxicity of mixtures of dimethylformamide (DMF) and methyl ethyl ketone (MEK) or DMF and toluene (TOL) and predicted their toxicity using quantitative structure-activity relationships (QSAR). A QSAR model for single substances and mixtures was analyzed using multiple linear regression (MLR) by taking into account the statistical parameters between the observed and predicted EC50. After preprocessing, the best subsets of descriptors in the learning methods were determined using a 5-fold cross-validation method. Significant differences in physico-chemical properties such as boiling point (BP), specific gravity (SG), Reid vapor pressure (rVP), flash point (FP), low explosion limit (LEL), and octanol/ water partition coefficient (Pow) were observed between the single substances and the mixtures. The EC50 of the mixture of DMF and TOL was significantly lower than that of DMF. The mixture toxicity was directly related to the mixing ratio of TOL and MEK (MLR EC50 equation = 1.76997 � 1.12249 × TOL + 1.21045 × MEK), as well as to SG, VP, and LEL (MLR equation EC50 = 15.44388 � 19.84549 × SG + 0.05091 × VP + 1.85846 × LEL). These results show that QSAR-based models can be used to quantitatively predict the toxicity of mixtures used in manufacturing industries.

Determination of three antidepressants in urine using simultaneous derivatization and temperature-assisted dispersive liquid-liquid microextraction followed by gas chromatography-flame ionization detection.

This paper presents a fast and simple method for the extraction, preconcentration and determination of fluvoxamine, nortriptyline and maprotiline in urine using simultaneous derivatization and temperature-assisted dispersive liquid-liquid microextraction (TA-DLLME) followed by gas chromatography-flame ionization detection (GC-FID). An appropriate mixture of dimethylformamide (disperser solvent), 1,1,2,2-tetrachloroethane (extraction solvent) and acetic anhydride (derivatization agent) was rapidly injected into the heated sample. Then the solution was cooled to room temperature and cloudy solution formed was centrifuged. Finally a portion of the sedimented phase was injected into the GC-FID. The effect of several factors affecting the performance of the method, including the selection of suitable extraction and disperser solvents and their volumes, volume of derivatization agent, temperature, salt addition, pH and centrifugation time and speed were investigated and optimized. Figures of merit of the proposed method, such as linearity (r(2) > 0.993), enrichment factors (820-1070), limits of detection (2-4 ng mL(-1)) and quantification (8-12 ng mL(-1)), and relative standard deviations (3-6%) for both intraday and interday precisions (concentration = 50 ng mL(-1)) were satisfactory for determination of the selected antidepressants. Finally the method was successfully applied to determine the target pharmaceuticals in urine.

Studies on kinetics and thermodynamics of oxidation of 3,4,5-trimethoxy benzaldehyde, benzaldehyde and N,N-dimethylamino benzaldehyde by tetraethylammonium bromochromate in dimethyl formamide and acetic acid mixture

The oxidation of 3,4,5-trimethoxy benzaldehyde (TMBA), benzaldehyde (BA) and dimethylamino benzaldehyde (DMABA) in N,N-dimethyl formamide (DMF) by tetraethylammonium bromochromate (TEABC) resulted in the formation of the corresponding acids. The reaction is first order with respect to both TEABC and the aldehydes. The reaction is catalyzed by toluene-p-sulfonic acid (p-TsOH). The hydrogen ion dependence has the form: kobs=a+b [H+]. The reaction has been studied in different percentage of DMF–acetic acid mixture. The effect of dielectric constant of the medium indicates the reaction to be of ion–dipole type. Various thermodynamic parameters for the oxidation have been reported and discussed along with the validity of isokinetic relationship. Reason for high rate in the case of oxidation of N,N-dimethylamino benzaldehyde is also described. A mechanism involving formation of a chromate ester intermediate in the slow step has been proposed.

Thermodynamic study of complex formation between Ce3+ and cryptand 222 in some binary mixed nonaqueous solvents

The stoichiometry, stability and the thermodynamic parameters of complex formation between cerium(III) cation and cryptand 222 (4,7,13,16,21,24-hexaoxa-1,10-diazabycyclo[8.8.8]-hexacosane) were studied by conductometric titration method in some binary solvent mixtures of dimethylformamide (DMF), 1,2-dichloroethane (DCE), ethyl acetate (EtOAc) and methyl acetate (MeOAc) with methanol (MeOH), at 288, 298, 308, and 318 K. A model based on 1: 1 stoichiometry has been used to analyze the conductivity data. The data have been fitted according to a non-linear least-squares analysis that provide the stability constant, K f, for the cation-ligand inclusion complex. The results revealed that the stability order of [Ce(cryptand 222)]3+ complex changes with the nature and composition of the solvent system. A non-linear relationship was observed between the stability constant (logK f) of [Ce(cryptand 222)]3+ complex versus the composition of the binary mixed solvent. Standard thermodynamic values were obtained from temperature dependence of the stability constant of the complex, show that the studied complexation process is mainly entropy governed and are influenced by the nature and composition of the binary mixed solvent solutions.

Growth control of cobalt oxide nanoparticles on reduced graphene oxide for enhancement of electrochemical capacitance

The high capacitance and cyclic stability of graphene nanosheets decorated with Co3O4 nanoparticles as a material for supercapacitor electrodes are reported here. Hydrothermal method is adopted to deposit cobalt oxides on the reduced graphene oxide (RGO) sheets in a mixture of water and dimethylformamide (DMF) as the solvent with different volume ratios. The water volume ratio presents a crucial factor in the nucleation and growth process. In addition, it affects dispersion, particle size and the amount of nucleated cobalt oxide particle on the graphene sheets. By decreasing the water volume, the nucleation and growth occur mainly on graphene rather than in solution. According to the obtained results from transmission electron microscopy, scanning electron microscopy and thermogravimetric analysis, a model for growth of nanoparticles on graphene sheets is proposed. Based on the obtained results, the presented model can also be used for the synthesis of other graphene-metal (oxide) composites. Electrochemical measurements indicate that water volume ratio in the mixture solvent influences on capacitance of the RGO/Co3O4 composite electrodes. The highest obtained specific capacitance is 440.4 F g−1 with 50% volume ratio of water at current density of 5 A g−1.

Effect of Solution Properties on Electrospun Chlorinated Polyvinyl Chloride Nanofibers

A kind of novel biodegradable Chlorinated Polyvinyl Chloride (CPVC) nanofibers using a mixture of Dimethyl Formamide (DMF) and Tetrahydrofuran (THF) as solvent were prepared by electrospinning process in this paper. The morphology of electrospun CPVC nanofiber nonwovens were investigated by scanning electron microscopy (SEM). Results indicated that the morphology and diameter of the electrospun fibers were influenced by CPVC solution concentration and the THF amount in the mixed solvents, and the finer and uniform nanofibers were electrospun from a mixed solvent of DMF and THF with ratio of 3/1(w/w).

Comparative Study on the EC50 Value in Single and Mixtures of Dimethylformamide, Methyl Ethyl Ketone, and Toluene.

The aim of this research was to improve our understanding of human toxicity due to exposure to DMF, MEK, or TOL individually as compared to exposure to DMF-MEK or DMF-TOL mixtures, by comparing EC50 values as well as the morphological changes in HepG2 cells treated with these substances. We found that there was marked cell necrosis in the groups treated with mixtures than in those treated with the compounds alone, and that the amount of cell death and the EC50 value were more dependent on MEK and TOL than on DMF. Moreover, analysis of the changes in effective concentration curves revealed that MEK had an antagonistic effect on the human toxicity of DMF, whereas TOL had a synergistic effect. Accordingly, these results suggest that in workplaces involved in the manufacture of synthetic leather, mixtures of DMF and TOL should be avoided as much as possible in order to minimize environmental toxicity and protect the health of the workers.

Effect of Acetone on Physical Properties of PES Membrane

In the present study, polyethersulfone (PES) dope solution were prepared from mixtures of two solvents containing dimethylformamide (DMF) as core solvent, and acetone as co-solvent (CS), deionized water was used as coagulant bath. The amount of PES was kept at 20 wt% and the weight ratios of acetone were varied 20-24 wt.% to DMF and the dope solutions were prepared under closed heating system Results revealed the complete miscibility of PES with the fixed mixture of acetone and DMF under atmospheric pressure. The relationships between degree of adsorption, relative water absorption, were investigated. The results revealed that the interaction of DMF and acetone is strongest when their mole ratio is unity, which exhibit the phenomenon of true cosolvency for PES membrane. Keywords: polyethersulfone, solvent mixture, characterization.

합성피혁제조업에서 취급하는 DMF, MEK, Toluene의 단일과 혼합물질 상태에 따른 물리·화학적 특성 변화

Objectives: It was known that workers in synthetic leather company are mainly co-exposed to dimethylformamide(DMF) with methyl ethyl ketone(MEK) or toluene(TOL) instead of a single dimethylformamide. This study was examined to the physico-chemical properties in single DMF and binary mixture DMF with MEK or TOL. Materials: Physico-chemical properties were measured by Korean and American Standard Test Methods. Results: Boiling point, specific gravity and flash point in single DMF were significantly higher than binary mixture DMF with MEK or TOL and such difference was dependent on the mixing ratio of MEK and TOL, and low explosion limit in binary mixture DMF with TOL was only significantly lower than single DMF. However, Reid vapor pressure had significantly higher in binary mixture DMF with MEK or TOL compared with single DMF. Conclusions: Our results demonstrate that the binary mixture DMF with MEK or TOL synergistically increases volatilization of DMF. It was concluded that the interaction between DMF and MEK and/or TOL might play a key role in the volatilization process of DMF under environmental conditions of workplace.

Nuclear magnetic resonance study of the stoichiometry and stability of several HgX2–acetylemethylentriparatolylphosphorane complexes in various acetone–dimethylformamide mixtures

The reaction of phosphorus ylide, acetylmethylenetriparatolylphosphorane (L) with HgX2 (X = Cl, Br, I and NO3) in equimolar ratios using acetone and dimethylformamide as solvents leads to binuclear products. 31P NMR spectroscopy was used to investigate the stoichiometry and stability of a HgX2 complex with CH3COCHP(p-tolyl)3 (L) in binary acetone–dimethylformamide mixtures of varying composition. In all cases studied, the variation of 31P NMR chemical shift with the [HgX2]/[L] mole ratio indicated the formation of 1:1 complexes. The formation constants of the resulting complexes were evaluated from computer fitting of the mole ratio data to an equation that relates the observed chemical shifts to the formation constant. In all mercuric salts used, the stabilities of the resulting 1:1 complexes varied in the order Hg(NO3)2 > HgCl2 > HgBr2 > HgI2. It was found that, in the case of all complexes, an increase in the percentage of dimethylformamide in the solvent mixtures significantly decreases the stability of the complexes.

Sensitivity of pressure sensors enhanced by doping silver nanowires.

We have developed a highly sensitive flexible pressure sensor based on a piezopolymer and silver nanowires (AgNWs) composite. The composite nanofiber webs are made by electrospinning mixed solutions of poly(inylidene fluoride) (PVDF) and Ag NWs in a cosolvent mixture of dimethyl formamide and acetone. The diameter of the fibers ranges from 200 nm to 500 nm, as demonstrated by SEM images. FTIR and XRD results reveal that doping Ag NWs into PVDF greatly enhances the content of β phase in PVDF. This β phase increase can be attributed to interactions between the Ag NWs and the PVDF matrix, which forces the polymer chains to be embedded into the β phase crystalline. The sensitivity of the pressure sensors agrees well with the FTIR and XRD characteristics. In our experiments, the measured sensitivity reached up to 30 pC/N for the nanofiber webs containing 1.5 wt% Ag NWs, which is close to that of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE), (77/23)]. This study may provide a new method of fabricating high performance flexible sensors at relatively low cost compared with sensors based on [P(VDF-TrFE), (77/23)].

True molecular solutions of natural cellulose in the binary ionic liquid-containing solvent mixtures

Evidence is presented for the first time of true molecular dissolution of cellulose in binary mixtures of common polar organic solvents with ionic liquid. Cryogenic transmission electron microscopy, small-angle neutron-, X-ray- and static light scattering were used to investigate the structure of cellulose solutions in mixture of dimethyl formamide and 1-ethyl-3-methylimidazolium acetate. Structural information on the dissolved chains (average molecular weight ∼5×104g/mol; gyration radius ∼36nm, persistence length ∼4.5nm), indicate the absence of significant aggregation of the dissolved chains and the calculated value of the second virial coefficient ∼2.45×10–2molml/g2 indicates that this solvent system is a good solvent for cellulose. More facile dissolution of cellulose could be achieved in solvent mixtures that exhibit the highest electrical conductivity. Highly concentrated cellulose solution in pure ionic liquid (27wt.%) prepared according to novel method, utilizing the rapid evaporation of a volatile co-solvent in binary solvent mixtures at superheated conditions, shows insignificant cellulose molecular aggregation.