Mixture Of Dimethylacetamide Research Articles

Nanostructured Carbon Fibres (NCF): Fabrication and Application in Supercapacitor Electrode.

A facile interconnected nanofibre electrode material derived from polybenzimidazol (PBI) was fabricated for a supercapacitor using a centrifugal spinning technique. The PBI solution in a mixture of dimethyl acetamide (DMA) and N, N-dimethylformamide (DMF) was electrospun to an interconnection of fine nanofibres. The as-prepared material was characterised by using various techniques, which include scanning electron microscopy (SEM), X-ray diffractometry (XRD), Raman, X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) among others. The specific surface area of the interconnected NCF material was noticed to be around 49 m2 g-1. Electrochemical properties of the material prepared as a single-electrode are methodically studied by adopting cyclic voltammetry, electrochemical impedance spectroscopy, and constant-current charge-discharge techniques. A maximum specific capacitance of 78.4 F g-1 was observed for the electrode at a specific current of 0.5 A g-1 in a 2.5 M KNO3 solution. The electrode could also retain 96.7% of its initial capacitance after a 5000 charge-discharge cycles at 5 A g-1. The observed capacitance and good cycling stability of the electrode are supported by its specific surface area, pore volume, and conductivity. The results obtained for this material indicate its potential as suitable candidate electrode for supercapacitor application.

Electrospinning of polyvinylidene fluoride membranes: effect of membrane composition and fabrication conditions

Membrane fabrication by the electrospinning can provide tunable structure membranes with interconnected pores, large surface area, and high porosity. This study focuses on studying the effect of different membrane compositions (i.e., polymer concentration and inorganic additives) and electrospinning conditions (i.e., internal needle diameter, tip to collector distance, and feed flow rate) on the quality of polyvinylidene fluoride (PVDF) flat sheet membrane. A homogeneous dope solution was prepared by dissolving the PVDF in a mixture of dimethylacetamide (DMAc) and acetone. By using a scanning electron microscope (SEM), the electrospinning conditions producing beadles fibers are as follows: 16 wt% polymer concentration, 0.004 wt% LiCl concentration, 0.51 mm internal needle diameter, 15 cm tip to collector distance, feed flow rate of 1 ml/hr. Further analysis was conducted by using Fourier Transform Infrared Spectrometer (FTIR) and X-Ray Diffraction (XRD) to assess the impact of electrospinning on fibers elemental composition. Additionally, static water contact angle, porosity, fiber diameter, and pore size measurements reveal the formation of submicron hydrophobic fibers with random alignment.

Morphology control in PVDF membranes using PEG/PVP additives and mixed solvents

The effects of the mixed two solvents, Dimethylacetamide (DMAc) and Dimethylformamide (DMF), and Polyethylene glycol (PEG) and Polyvinylpyrrolidone (PVP) as additives on performance of Polyvinylidene fluoride (PVDF) membranes were studied. Initially, PEG200 was used as a primary additive at fixed percentage of 5% wt. PVP was then blended with PEG200 in different concentrations. PVDF and DMAc were used as polymer and solvent in the casting solutions, respectively. To control the diffusion rate of PVP in the presence of PEG200 and PVP blend, mixtures of DMAc and DMF were used as the mixed solvent in the casting solutions. Asymmetric PVDF membranes were prepared via phase inversion process in a water bath and the effects of two additives and two solvents on the membrane morphology, pure water flux (PWF), hydrophilicity and rejection (R) were investigated. Attenuated Total Reflection Fourier Transform Infrared Spectra (ATR-FTIR) analysis was used to show the residual PVP on the surface of the membranes. Atomic Force Microscopy (AFM) was utilized to determine roughness of membrane surface. The use of mixed solvents in the casting solution resulted in reduction of PVP diffusion rate and increment of PEG diffusion rate. Eventually, PWF and R values reduced, while porosity and hydrophilicity increased.

Spectroscopic Characterisation of a Bio-Inspired Ni-Based Proton Reduction Catalyst Bearing a Pentadentate N2 S3 Ligand with Improved Photocatalytic Activity.

Inspired by the sulfur-rich environment found in active hydrogenase enzymes, a Ni-based proton reduction catalyst with pentadentate N2 S3 ligand was synthesised. When coupled with [Ru(bpy)3 ]2+ (bpy=2,2'-bipyridine) as photosensitiser and ascorbate as electron donor in a 1:1 mixture of dimethylacetamide and aqueous ascorbic acid/ascorbate buffer, the catalyst showed improved photocatalytic activity compared with a homologous counterpart bearing a tetradentate N2 S2 ligand. The mechanistic pathway of photoinduced hydrogen evolution was comprehensively analysed through optical transient absorption and time-resolved X-ray absorption spectroscopy, which revealed important electronic and structural changes in the catalytic system during photoirradiation. The NiII catalyst undergoes a photoinduced metal-centred reduction to form a NiI intermediate with distorted square-bipyramidal geometry. Further kinetic analyses revealed differences in charge-separation dynamics between the pentadentate and tetradentate forms.

Copper-mediated homogeneous living radical polymerization of acrylamide with waxy potato starch-based macroinitiator

Cu0-mediated living radical polymerization (Cu0-mediated LRP) was employed in this research for the synthesis of starch-g-polyacrylamide (St-g-PAM). The use of a controlled radical grafting technique is necessary, as compared to the traditional free-radical polymerization methods, in order to obtain a well-defined structure of the final product. This is in turn essential for studying the relationship between such structure and the end-properties. Waxy potato starch-based water-soluble macroinitiator was first synthesized by esterification with 2-bromopropionyl bromide in the mixture of dimethylacetamide and lithium chloride. With the obtained macroinitiator, St-g-PAM was homogeneously synthesized by aqueous Cu0-mediated LRP using CuBr/hexamethylated tris(2-aminoethyl)amine (Me6Tren) as catalyst. The successful synthesis of the macroinitiator and St-g-PAM was proved by NMR, FT-IR, SEM, XRD and TGA analysis. The molecular weight and polydispersity of PAM chains were analyzed by gel permeation chromatography (GPC) after hydrolyzing the starch backbone. Monomer conversion was monitored by gas chromatography (GC), on the basis of which the kinetics were determined. A preliminarily rheological study was performed on aqueous solutions of the prepared materials.

Dielectric characterization and molecular interaction behavior in amide–amide binary mixture

ABSTRACTThe frequency dependent dielectric relaxation spectra for binary mixture of dimethylacetamide with formamide and dimethylformamide at 11 different concentrations at 30°C over frequency range 10 MHz to 20 GHz is studied. The mixture exhibit a principle dispersion of the Davidson-Cole relaxation type. Dielectric constant (ϵ0), relaxation time (τ), excess dielectric constant (ϵE), excess inverse relaxation time (1/τ)E and Kirkwood correlation factor (g) have been determined and discussed in terms of the effect of NH2 and –CH3 side group on molecular dynamics and intermolecular hydrogen bonds. Conformational analysis of the formation of hydrogen bond is supported by the FTIR study.

Buccal adhesive nanofibers containing human growth hormone for oral mucositis.

Due to a lack of proper drug carriers to deliver treatments for mucositis, many cancer patients suffer from oral mucositis caused by chemotherapy and radiotherapy. We prepared a double-layered electrospun nanofibrous sheets composed of Eudragit and chitosan to accelerate the healing rate of oral mucous ulcer. Human growth hormone (hGH) and Eudragit in a mixture of dimethylacetamide and ethanol were co-electrospun to nanofibrous sheets. The electrospun fibrous mat was subsequently layered with chitosan by a dip-coating method. Chitosan-layered sheets showed attenuated mass erosion while uncoated sheets were instantly melted at the physiological condition. The released hGH was trapped on the chitosan layer by the ionic interaction between positively charged chitosan and negatively charged hGH, and a large number of entrapped proteins remained on the SIS membrane due to the muco-adhesive properties of chitosan. hGH-incorporated sheets significantly increased proliferation of human dermal fibroblasts. In vivo study employing oral ulcers in dogs, the ulcers dressed with chitosan-layered sheets showed enhanced wound recovery and the chitosan layers on the sheet greatly assisted prolonged recovery. Therefore, chitosan-layered Eudragit nanofibrous sheets can be potentially applied to developing muco-adhesive wound dressing materials with pH-dependent drug release by adjusting the thickness of chitosan sheath on the sheets. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1396-1406, 2016.

Molecular interaction studies in ternary liquid mixture of dimethylacetamide using ultrasonic technique at 308 K

The experimental density (ρ) and ultrasonic velocity (U) for ternary mixture containing dimethylacetamide (DMAC), acetone and diethyl ether at frequencies 2, 4, 6 and 8 MHz have been measured at temperature 308 K. These data are used to compute adiabatic compressibility (Ks), intermolecular free length (Lf), acoustic Impedance (Z), molar volume (Vm), molar sound velocity (R), molar compressibility (B), available volume (Va), Lennard-Jones potential repulsive term exponent (n), relative association (RA), interaction parameter (χ) and some excess thermo acoustic parameters for whole range of concentration of DMAC and are interpreted to elucidate molecular interaction occurring in the liquid mixture.

Temperature-dependent dielectric characterisation and molecular interaction behaviour in binary mixtures of dimethylacetamide with ethylene glycol and dimethylsulphoxide

Dielectric relaxation measurements on binary mixtures of dimethylacetamide with ethylene glycol and dimethylsulphoxide have been carried out at 11 concentrations using time domain reflectometry technique at 10°C, 20°C, 30°C and 40°C over the frequency range from 10 MHz to 10 GHz. For all the mixtures, only one dielectric loss peak is observed in this frequency range. The relaxation in these mixtures can be described by a single relaxation time using the Debye model. A systematic variation is observed in dielectric constant and relaxation time. Excess permittivity, excess inverse relaxation time, Kirkwood correlation factor and thermodynamic parameters such as enthalpy of activation and Gibbs free energy of activation have been determined, to confirm the formation of hydrogen-bonded homogeneous and heterogeneous cooperative domains, the dynamics of solute–solvent interaction and the hindrance to molecular rotation in the hydrogen-bonded glass forming ethylene glycol–dimethylacetamide and dimethylsulphoxide–dimethylacetamide system.

Nylon 3 synthesized by ring opening polymerization with a metal-free catalyst

We have synthesized nylon 3 via ring opening polymerization of 2-azetidinone (β-lactam) with 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)- phosphoranylidenamino]-2Λ5,4Λ5-catenadi(phosphazene) (t-BuP4) as the catalyst in a mixture of dimethylacetamide (DMAc) and LiCl. The polymers have been characterized by nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), laser light scattering (LLS) and viscometry. The synthesized nylon 3 is a linear and crystalline polymer with a molecular weight as high as 105 g mol−1. The intrinsic viscosity ([η]) relates to the weight average molecular weight (Mw) as [η] = 1.02 × 10−4Mw0.91. The effects of solvent, temperature and catalyst concentration on the polymerization have been examined. The molecular weight and yield increases with the amount of LiCl in the polymerization mixture, but both of them decrease with temperature at a temperature above 50 °C. As the catalyst concentration increases, the yield and the molecular weight of nylon 3 decrease. The possible mechanism for the initiation of polymerization is discussed.

Effect of dielectric constant of solvent on the conductivity behavior of polymer gel electrolytes

Non aqueous polymer gel electrolytes are currently attracting considerable attention due to their use as electrolytes in solid state batteries, fuel cells, supercapacitors, etc. [1–3]. Polymer gel electrolytes belong to a salt–solvent-polymer hybrid system in which the salt solution is immobilized with the addition of a suitable polymer matrix [4, 5]. The solvent helps in the dissociation of the salt and also provides a conducting medium and should generally have high dielectric constant— which ensures the dissociation of salt, low viscosity— which shall result in higher mobility and low melting point and high boiling point—so that the electrolyte could be used over a wide range of temperature [6]. If a single solvent with suitable properties is not available, then a binary/ternary solvent mixture can also be used [7]. The addition of polymer to salt solution increases the viscosity of the electrolytes accompanied by a small decrease in conductivity, which suggests that the polymer generally plays the role of a stiffener only [8–10]. However recent results on proton conducting polymer gel electrolytes containing weak acids indicate that the addition of polymer can also lead to an increase in the conductivity and gel electrolytes with conductivity higher than the corresponding liquid electrolytes have been reported [11, 12]. This increase in conductivity with polymer addition has been found to depend upon the dissociation constant of acid, dielectric constant of solvent and molecular weight of the polymer used [6, 13, 14]. The present study has been undertaken to investigate the role of the dielectric constant of the solvent on the conductivity behavior of polymer gel electrolytes. Lithium ion conducting polymer gel electrolytes containing lithium trifluoromethanesulphonate (LiCF3SO3), different single/binary solvents based on dimethylacetamide (DMA) and diethylcarbonate (DEC) with polymethylmethacrylate (PMMA) as the gelling polymer have been synthesized and the variation of conductivity and viscosity with the concentration of salt, polymer and the dielectric constant (e) of the solvent has been studied. Liquid electrolytes were prepared by dissolving LiCF3SO3 in different concentrations (expressed as molarity values) in DMA, DEC and in binary mixtures of DMA and DEC taken in different volume ratios. Polymer gel electrolytes were then obtained by adding PMMA in different ratios (expressed as wt.% of liquid

Microwave Dielectric Characterization of Binary Mixtures of 3-Nitrotoluene with Dimethylacetamide, Dimethylformamide and Dimethylsulphoxide

Dielectric relaxation measurements on 3-nitrotoluene (3-NT) mixture of dimethylacetamide (DMA), dimethylformamide (DMF) and dimethysulphoxide (DMSO) have been carried out across the entire concentration range using Time domain reflectometry technique at 15, 25, 35 and <TEX>$45^{\circ}C$</TEX> over the frequency range from 10 MHz to 20 GHz. For all the mixtures, only one dielectric loss peak was observed in this frequency range and the relaxation in these mixtures can be well described by a single relaxation time using Debye model. Bilinear calibration method is used to obtain complex permittivity <TEX>${\varepsilon}^{*}({\omega})$</TEX> from complex reflection coefficient <TEX>${\rho}^{*}({\omega})$</TEX> over frequency range 10 MHz to 20 GHz. The excess permittivity, excess inverse relaxation time, Kirkwood correlation factor, molar energy of activation are also calculated for these mixtures to study the solute-solvent interaction.

Uv Spectroscopy in Monitoring of Biological Treatment of Washing Waters from Aromatic Polyamide Fibre Production

Aromatic polyamide fibre production wastes — aqueous solutions consisting of a mixture of dimethylacetamide and isobutyl alcohol, initial and treated with microorganisms for different times — were analyzed. Monitoring solutions with absorption in the UV region and COD allowed following biological treatment and modeling its components of the solutions. The possibility of monitoring biological treatment by UV spectroscopy was demonstrated.

Extended Hildebrand Solubility Approach: Sulfonamides in Binary and Ternary Solvents

The extended Hildebrand solubility approach is used to estimate the solubility of sulfonamides in binary and ternary solvent systems. The solubility of sulfisomidine in the binary solvent, dioxane–water, shows a bell-shaped profile with a solubility maximum well above the ideal solubility of the drug. This is attributed to solvation of the drug with the dioxane–water solvent, and indicates that the solute–solvent interaction energy (W) is larger than the geometric mean (δ1δ2) of regular solution theory. The solubilities of sulfadiazine, sulfisomidine, sulfathiazole, and sulfamethoxazole were determined in mixtures of dimethylacetamide, glycerol, and water, and the solubility profiles were well reproduced by use of the extended Hildebrand solubility approach. Since the solubility parameter (δ1 = 11) of the solvent (dimethylacetamide) was approximately equal to the solubility parameters of the sulfonamides, and because of the powerful solvating power of dimethylacetamide, the solubility profiles did not exhibit peaks as observed for sulfisomidine in dioxane–water. When sulfisomidine was dissolved in a ternary mixture, i.e., butyl acetate (δ1 = 8.5), dimethylacetamide (δ1 ≃ 11), and methanol (δ1 = 14.5), a spike was produced in the solubility profile at the solubility parameter of dimethylacetamide. This sharply peaked profile suggests that the two branches be treated as separate solubility curves, which are then independently well reproduced by the extended Hildebrand solubility approach. None of the four sulfonamides yielded log-linear relationships in the ternary mixtures.

Effect of traces of water in the solvent on the heat of solution of terephthaloyl chloride in the amide-salt system

The dependence of the heat of solution of terephthaloyl chloride in a mixture of dimethylacetamide and 3% lithium chloride on small amounts of water in the solvent (0.01–0.5% by wt.) has been determined, using a Calvet microcalorimeter. It has been shown that hydrolysis of the acid chloride takes place in the amide-salt system in the presence of water.

Reversible gelation of acrylonitrile–vinyl acetate copolymer solutions. II. Mechanical properties

AbstractConcentrated solutions of acrylonitrile polymers exhibit reversible gelation. The rate of gelation at 25°C. was determined for various solutions of an acrylonitrile copolymer containing 7.7% vinyl acetate in mixtures of dimethylacetamide (solvent) and water (nonsolvent) by measuring the shear modulus of the forming gel as a function of time. The mechanical properties were also measured on a series of gels formed by cooling solutions to −78°C. It was found that both the rate of gelation at 25°C. and the modulus of gels formed at −78°C. increase very rapidly as either the solids level of the solution of the water content of the solvent is increased. The gelation rate data wree correlated with the gel melting points of the gels. The results are discussed and compared with the analogous but limited data available for other systems.