Dimethylformamide Concentration Research Articles

Preparation of polyvinylchloride membranes from solvent mixture by immersion precipitation

AbstractIn this study, polyvinylchloride (PVC) membranes were prepared through the immersion precipitation method using a mixture of two solvents (tetrahydrofuran (THF) and dimethyl formamide (DMF)), which had different affinities with the nonsolvent (water). Membranes prepared from PVC/THF/water system showed a sponge‐like structure with isolated pores, which were impermeable to water even at a feed pressure of 20 bars, whereas those prepared from PVC/DMF/water exhibited a porous macrovoid containing morphology with a high water flux. The precipitation time and polymer concentration profiles were calculated by using a simple mathematical model and were in good agreement with the experimental findings on PVC/THF/water and PVC/DMF/water systems. By using a mixture of DMF and THF as solvent and changing the mixed solvent composition, membranes with different morphologies from sponge‐like to macrovoid containing were obtained. The membranes showed no water flux below a DMF concentration of 50 wt % and then became increasingly permeable with increasing DMF content in the casting solution. Measurement of the system cloud points showed a linear change of system thermodynamics with variation of the mixed solvent composition. The obtained results showed that although the system thermodynamics could explain the overall behavior of the system, but the local changes such as change of membrane performance from impermeable to permeable at a certain mixed solvent composition could not be explained by the thermodynamics alone. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40206.

Electrospun preparation of microporous carbon ultrafine fibers with tuned diameter, pore structure and hydrophobicity from phenolic resin

Microporous carbon ultrafine fibers with different diameter were prepared by electrospinning from resole-type phenolic resin, followed by heat curing and one-step carbonization, and their adsorption performance for benzene and water was evaluated. Average diameter of as-spun fibers changed from 1.1 to 0.33μm with increasing dimethylformamide content in the spinning solution, caused by more fiber divisions. The carbon ultrafine fibers with smaller diameter exhibited enhanced benzene adsorption and diminished water adsorption due to improved specific surface area, micropore volume and hydrophobicity. In addition, the relatively developed hydrophobicity of the prepared carbon ultrafine fibers resulted in much higher adsorption tendency for benzene over water, in comparison to common polyacrylonitrile-based electrospun activated carbon nanofibers.

Ibuprofen-loaded poly(trimethylene carbonate-co-ε-caprolactone) electrospun fibres for nerve regeneration

The development of scaffolds that combine the delivery of drugs with the physical support provided by electrospun fibres holds great potential in the field of nerve regeneration. Here it is proposed the incorporation of ibuprofen, a well-known non-steroidal anti-inflammatory drug, in electrospun fibres of the statistical copolymer poly(trimethylene carbonate-co-ε-caprolactone) [P(TMC-CL)] to serve as a drug delivery system to enhance axonal regeneration in the context of a spinal cord lesion, by limiting the inflammatory response. P(TMC-CL) fibres were electrospun from mixtures of dichloromethane (DCM) and dimethylformamide (DMF). The solvent mixture applied influenced fibre morphology, as well as mean fibre diameter, which decreased as the DMF content in solution increased. Ibuprofen-loaded fibres were prepared from P(TMC-CL) solutions containing 5% ibuprofen (w/w of polymer). Increasing drug content to 10% led to jet instability, resulting in the formation of a less homogeneous fibrous mesh. Under the optimized conditions, drug-loading efficiency was above 80%. Confocal Raman mapping showed no preferential distribution of ibuprofen in P(TMC-CL) fibres. Under physiological conditions ibuprofen was released in 24 h. The release process being diffusion-dependent for fibres prepared from DCM solutions, in contrast to fibres prepared from DCM-DMF mixtures where burst release occurred. The biological activity of the drug released was demonstrated using human-derived macrophages. The release of prostaglandin E2 to the cell culture medium was reduced when cells were incubated with ibuprofen-loaded P(TMC-CL) fibres, confirming the biological significance of the drug delivery strategy presented. Overall, this study constitutes an important contribution to the design of a P(TMC-CL)-based nerve conduit with anti-inflammatory properties.

Selective Determination of Uranium Using 1-(2-Quinolylazo)-2,4,5-Trihydroxybenzene as a Colorimetric Reagent

Colorimetric reaction behavior of 1-(2-quinolylazo)-2,4,5-trihydroxybenzene (QATB) has been established with uranium(VI) under various physicochemical conditions. An addition of dilute solution of uranyl ions to the dimethylformamide (DMF) solution of QATB, resulted to form a brown colored complex which was soluble if 30% DMF concentration was maintained. The brown colored complex absorbing maximum at 560 nm in the pH range 6.5-7.5. Beer's law was valid over concentration range 0.0-14.0 ppm, with molar absorptivity and Sandell's sensitivity of 1.9 x 10 4 L.mol. -1 cm -1 and 0.0125 µg cm 2 , respectively. The molar composition of the complex was 1:2 (M:L) as determined by Job's method of continuous variation. The tolerance limits for interfering ions are discussed. All variables were studied in order to optimize the reaction conditions. The efficiency of the proposed method is shown by the successful determination of traces of uranium in some ores.

Synthesis, characterisation and aggregation properties of novel metal-free and metallophthalocyanines containing four 21-membered oxatetrathiadiaza macrocycles

The synthesis of novel metal-free phthalocyanine 4 and metallophthalocyanines 5, 6, 7 (MPcs, M = Ni, Zn, Co) containing four 21-membered oxatetrathiadiaza macrocycles at the peripheral positions was achieved by cyclotetramerisation of a novel 6,16-dioxo-5,6,7,9,10,12,13,15,16,17-decahydrotribenzo [h,k,n][1,4,10,13,19,7,16]oxatetrathiadiazacyclohenicosine-24,25-dicarbonitrile. The aggregation behaviours of phthalocyanines 4, 5, 6 and 7 were investigated at different concentrations in dimethylformamide. No aggregation behaviour was observed in dimethylformamide at concentrations between 10 × 10−6 and 1 × 10−6 mol dm−3. The aggregation properties of all phthalocyanines were also investigated in different solvents. All new compounds were characterised by a combination of elemental analysis and 1H NMR, 13C NMR, IR, UV–Vis and MS spectral data.

Preparation of porous nanofibers from electrospun polyacrylonitrile/calcium carbonate composite nanofibers using porogen leaching technique

AbstractProduction of nanofibrous polyacrylonitrile/calcium carbonate (PAN/CaCO3) nanocomposite web was carried out through solution electrospinning process. Pore generating nanoparticles were leached from the PAN matrices in hydrochloric acid bath with the purpose of producing an ultimate nanoporous structure. The possible interaction between CaCO3 nanoparticles and PAN functional groups was investigated. Atomic absorption method was used to measure the amount of extracted CaCO3 nanoparticles. Morphological observation showed nanofibers of 270–720 nm in diameter containing nanopores of 50–130 nm. Monitoring the governing parameters statistically, it was found that the amount of extraction (ε) of CaCO3was increased when the web surface area (a) was broadened according to a simple scaling law (ε = 3.18 a0.4). The leaching process was maximized in the presence of 5% v/v of acid in the extraction bath and 5 wt % of CaCO3 in the polymer solution. Collateral effects of the extraction time and temperature showed exponential growth within a favorable extremum at 50°C for 72 h. Concentration of dimethylformamide as the solvent had no significant impact on the extraction level. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013

Effects of N,N-dimethylformamide on behaviour and regeneration of planarian Dugesia japonica

In this study, the toxicity, behavioural and regeneration effects of dimethylformamide (DMF) on planarian Dugesia japonica were investigated. One control and six different concentrations of DMF (10ppm, 100ppm, 500ppm, 1000ppm, 5000ppm and 10,000ppm) were used in triplicate. The results showed that the mortality was directly proportional to the DMF concentration and planarian locomotor velocity (pLMV) was significantly reduced by increasing the exposure time and DMF concentration. pLMV of D. japonica was significantly reduced at a lower concentration of 10ppm after 7 days of continuous exposure to DMF. The recovery of the motility of planarians pretreated with DMF was found to be time- and dose dependent, all planarians had complete recovery in their motility after 48h. The appearance of auricles in regenerating animals was easily affected by DMF exposure in comparison with the appearance of eyespot. The present results suggest that the intact adult mobility in the aquatic planarian D. japonica is a more sensitive biomarker than mortality, and the appearance of auricles in regenerating animals is a more sensitive biomarker than eyespot.

PMMA Modified PVDF Hollow Fiber Ultrafiltration Membranes

Polymethylmethacrylate (PMMA) modified poly(vinylidene fluoride) (PVDF) hollow fiber ultrafiltration membranes were prepared by wet spinning method using polyvinylpyrrolidone (PVP) as pore-foaming agent and mixture of dimethyl formamide (DMF)/methyl ethyl ketone (MEK) as solvent. The effects of PVDF, PMMA, PVP, and solvent ratios in the spinning solution on the permeation properties of the formed membranes were studied. The results showed that the performance of the membrane is the best with a pure water flux of 117 L/m2•h and rejection rate of 82% to bovine serum albumin (BSA), when the concentrations of PVDF, PMMA, PVP, DMF and MEK are 17, 3, 3, 60 and 17 wt%, respectively.

Polymorph‐Dependent Solid‐State Fluorescence and Selective Metal‐Ion‐Sensor Properties of 2‐(2‐Hydroxyphenyl)‐4(3H)‐quinazolinone

2-(2-Hydroxy-phenyl)-4(3H)-quinazolinone (HPQ), an organic fluorescent material that exhibits fluorescence by the excited-state intramolecular proton-transfer (ESIPT) mechanism, forms two different polymorphs in tetrahydrofuran. The conformational twist between the phenyl and quinazolinone rings of HPQ leads to different molecular packing in the solid state, giving structures that show solid-state fluorescence at 497 and 511 nm. HPQ also shows intense fluorescence in dimethyl formamide (DMF) solution and selectively detects Zn(2+) and Cd(2+) ions at micromolar concentrations in DMF. Importantly, HPQ not only detects Zn(2+) and Cd(2+) ions selectively, but it also distinguishes between the metal ions with a fluorescence λ(max) that is blue-shifted from 497 to 420 and 426 nm for Zn(2+) and Cd(2+) ions, respectively. Hence, tunable solid-state fluorescence and selective metal-ion-sensor properties were demonstrated in a single organic material.

Preparation and characterization of poly (vinyl chloride)-blend-poly (carbonate) heterogeneous cation exchange membrane: Investigation of solvent type and ratio effects

In this research polyvinylchloride/polycarbonate blend heterogeneous cation exchange membranes were prepared by solution casting technique using cation exchange resin powder as functional groups agent. Tetrahydrofuran (THF) and dimethylformamide (DMF) were utilized as solvents. The effect of solvent type and ratio (THF/DMF mixture) on properties of prepared membranes was studied. SEM and SOM images showed relatively uniform particle distribution and also uniform surface for the membranes. Images showed that at high DMF ratio decrease of polymer conformation with particles surface reduces the compatibility of polymer-particle. The membrane ion exchange capacity and permeability were enhanced initially by increase of DMF ratio up to 5% (v/v) in casting solution and then they began to decrease with more DMF ratio. Results showed that membrane potential, transport number, selectivity and thermal stability all were decreased by DMF ratio increasing. Conversely, membrane water content, specific surface area and roughness showed opposite trends. Membrane electrical resistance initially declined by increase in DMF content up to 15% (v/v) and then it began to increase. The increase of electrolyte concentration also led to decrease in membrane transport number and selectivity. Membrane with (95:5) (v/v) solvent ratio (THF:DMF) exhibited more appropriate performance compared to others.

Generation of continuous packed bed reactor with PVA–alginate blend immobilized Ochrobactrum sp. DGVK1 cells for effective removal of N, N-dimethylformamide from industrial effluents

Effective removal of dimethylformamide (DMF), the organic solvent found in industrial effluents of textile and pharma industries, was demonstrated by using free and immobilized cells of Ochrobactrum sp. DGVK1, a soil isolate capable of utilizing DMF as a sole source of carbon, nitrogen. The free cells have efficiently removed DMF from culture media and effluents, only when DMF concentration was less than 1% (v/v). Entrapment of cells either in alginate or in polyvinyl alcohol (PVA) failed to increase tolerance limits. However, the cells of Ochrobactrum sp. DGVK1 entrapped in PVA–alginate mixed matrix tolerated higher concentration of DMF (2.5%, v/v) and effectively removed DMF from industrial effluents. As determined through batch fermentation, these immobilized cells have retained viability and degradability for more than 20 cycles. A continuous packed bed reactor, generated by using PVA–alginate beads, efficiently removed DMF from industrial effluents, even in the presence of certain organic solvents frequently found in effluents along with DMF.

Pollutants Characterization of Spinning Effluents Containing Dimethyl Formamide from Dry-Spun Acrylic Fiber Manufacturing by Multi Scale Membrane Filtration

Spinning effluents (SE) from dry-spun acrylic fiber manufacturing are hard to biodegrade due to the high concentration of dimethyl formamide (DMF). This paper evaluated the pollutant distribution characteristics of SE by means of multi scale membrane filtritions, including microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Scanning electron microscopy (SEM) and nano particle size analyzer (NPSA) tests were also used as assistant measurements. The major pollutant diameters in SE range from 20 nm to 30 nm with a statistical median size of 300nm. The particulate, colloidal and soluble organic fractions contribute 8.44%, 37.13% and 54.43% to the initial COD. 11.4%, 13.67% and 71.92% of the initial DMF distributes in the particle, colloidal and soluble portion respectively. The data of ammonia are relevantly 22.17%, 11.45% and 56.38%, indicating that the soluble fraction, which is also poor in biodegradability, plays a key role in SE treatment. Beside, the majority of AN distributes in the soluble range while 90.98% of cyanide distributes in the particulate and supracolloidal portions.

Dimethylformamide as a cryoprotectant for canine semen diluted and frozen in ACP-106C

The objective was to assess the effect of adding various concentrations of dimethylformamide on characteristics of canine semen diluted in powdered coconut water (ACP-106C; ACP Biotecnologia, Fortaleza, CE, Brazil) and frozen at −196°C. Fifteen ejaculates were collected by manual stimulation from five adult Boxer dogs. The sperm-rich fraction was diluted in ACP-106C (ACP Biotecnologia) containing 10% egg yolk and divided into four aliquots. The cryoprotectants used for each aliquot were 6% glycerol (control group; CG) or 2%, 4%, or 6% dimethylformamide (DF2, DF4, and DF6, respectively). After thawing, total motility (mean ± SEM) for CG (58.4 ± 24.6) was higher (P < 0.05) than that of the other groups (2% dimethylformamide, 24.4 ± 12.3; 4% dimethylformamide, 26.5 ± 16.1; and 6% dimethylformamide, 21.7 ± 17.9). Furthermore, there was a greater percentage of fast, average, and slow moving sperm (assessed with computer-aided semen analysis; CASA) in CG in comparison with the other three groups. Therefore, based on concentrations tested in this study, dimethylformamide, together with ACP-106C (ACP Biotecnologia) and 10% egg yolk as a diluent, yielded unsatisfactory in vitro results for freezing canine semen.

The solubility of sulphadiazine in water-dimethyl-formamide mixtures.

Abstract Precise measurements of the solubility of sulphadiazine in water, dimethylformamide (DMF), and a range of mixtures of these solvents have been made at 20°, 30°, and 40°. The solubility of sulphadiazine in the mixtures increases with their DMF content. The partial molar heats and entropies of solution decrease with increasing DMF concentration.

Sterol carrier protein-2 (SCP-2) involvement in cholesterol hydroperoxide cytotoxicity as revealed by SCP-2 inhibitor effects

Sterol carrier protein-2 (SCP-2) plays an important role in cholesterol trafficking and metabolism in mammalian cells. The purpose of this study was to determine whether SCP-2, under oxidative stress conditions, might also traffic hydroperoxides of cholesterol, thereby disseminating their cytotoxic effects. Two inhibitors, SCPI-1 and SCPI-3, known to block cholesterol binding by an insect SCP-2, were used to investigate this. A mouse fibroblast transfectant clone (SC2F) overexpressing SCP-2 was found to be substantially more sensitive to apoptotic killing induced by liposomal 7α-hydroperoxycholesterol (7α-OOH) than a wild-type control. 7α-OOH uptake by SC2F cells and resulting apoptosis were both inhibited by SCPI-1 or SCPI-3 at a subtoxic concentration. Preceding cell death, reactive oxidant accumulation and loss of mitochondrial membrane potential were also strongly inhibited. Similar SCPI protection against 7α-OOH was observed with two other types of SCP-2-expressing mammalian cells. In striking contrast, neither inhibitor had any effect on H(2)O(2)-induced cell killing. To learn whether 7α-OOH cytotoxicity is due to uptake/transport by SCP-2, we used a fluorescence-based competitive binding assay involving recombinant SCP-2, NBD-cholesterol, and SCPI-1/SCPI-3 or 7α-OOH. The results clearly showed that 7α-OOH binds to SCP-2 in SCPI-inhibitable fashion. Our findings suggest that cellular SCP-2 not only binds and translocates cholesterol but also cholesterol hydroperoxides, thus expanding their redox toxicity and signaling ranges under oxidative stress conditions.

Electrospun composite nanofibers of poly (vinylidene fluoride‐trifluoroethylene)/polyaniline‐polystyrene sulfonic acid

AbstractNanofibers of poly(vinylidene fluoride‐trifluoroethylene)/polyaniline‐polystyrene sulfonic acid (PVDF‐TrFE/PANi‐PSSA) were fabricated in air at room temperature using electrospinning, with the thinnest fiber having a diameter of ∼ 6 nm. This is a cheap, fast, and reliable process for generating PVDF‐TrFE/PANi‐PSSA composite nanofibers. The presence of conducting PANi‐PSSA increased the charge density of the solution and assisted in the fabrication of PVDF‐TrFE nanofibers at low polymer concentrations in dimethylformamide without the beading effect. Ultraviolet and visible spectroscopy showed that PANi‐PSSA was well incorporated into the PVDF‐TrFE solution with no polymer segregation or degradation. A scanning electron microscope was used for morphological characterization of the fibers and a profilometer used to determine the fiber diameter. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Aggregation Behavior of Poly(ethylene glycol)-block-poly (γ-benzyl L-glutamate)-graft-poly(ethylene glycol) Copolymer and its Blends with Poly(γ-benzyl L-glutamate) Homopolymer in Mixed Solvents

Poly(ethylene glycol)-block-poly(γ-benzyl L-glutamate)-graft-poly(ethylene glycol) (PEG-b-PBLG-g-PEG) copolymer was synthesized by the ester exchange reaction of PBLG-block-PEG copolymer with mPEG. The self-association behaviors of PEG-b-PBLG-g-PEG and its blends with PBLG homopolymer in the mixtures of ethanol and dimethylformamide (DMF) were investigated by transmission electron microscopy (TEM), dynamic light scattering (DLS), and viscometry. Effects of the introduction of PBLG homopolymer, the grafting ratio, and the DMF content on the self-association behaviors of PEG-b-PBLG-g-PEG copolymer in the mixtures of ethanol and DMF were mainly researched. It was revealed that PEG-b-PBLG-g-PEG copolymer could self-assemble to form polymeric micelles with a core-shell structure in various shapes from different preparation conditions. The critical micelle concentration (CMC) and the average particle diameter of the micelles formed by PEG-b-PBLG-g-PEG copolymer in the mixed solvents also changed with different preparation conditions.

Investigation on dermal contamination among workers occupationally exposed to dimethylformamide

To establish a method for the determination of dimethylformamide (DMF) and investigate dermal contamination and absorption among workers occupationally exposed to DMF. 37 workers exposed to DMF were divided randomly into two groups. DMF was washed down by isopropyl alcohol in A group (16 workers) and water in B group(21 workers).Gas chromatography was used for the quantification of dermal contamination and N-methylformamide(NMF) in urine, correlative study was done between them. DMF could be detected in all samples in A group, but could not be detected in B group. The miscellaneous peaks could be completely separated from the DMF peak in the sample spectrum, without manual inference. The highest degree of total dermal contamination was observed in wet spinning workshop [(2.84 +/- 1.31) mg], postprocessing workshop [(2.50 +/- 0.95) mg] and dry spinning workshop [(1.95 +/- 0.61) mg] were lower. The respiratory cumulative exposure dosages were 351.3, 201.3 and 135.2 mg respectively. The average DMP concentration in air of the third printing processing workshop, the dry spinning workshop and the wet spinning workshop was 60.2, 89.6, 156.4 mg/m3 respectively, and the respiratory tract contamination in the workers of the three workshops were 135.2, 201.3 and 351.3 mg respectively. There was statistical independence between the quantification of total dermal contamination and NMF in urine (r = 0.176, P > 0.05). Isopropyl alcohol is the effective washing solvent.When the concentration of DMF in workplace air is above the occupational exposure limit, respiratory tract absorption is the principal pathway of DMF absorption,but dermal contamination of DMF should not be ignored.

Residues Contributing to the Na+-binding Pocket of the SLC24 Na+/Ca2+-K+ Exchanger NCKX2

Na(+)/Ca(2+)-K(+) exchangers (NCKX; gene family SLC24) are plasma membrane Ca(2+) transporters that mediate the extrusion of one Ca(2+) ion and one K(+) ion in exchange for four Na(+) ions. NCKX is modeled to have two sets of five transmembrane segments separated by a large cytosolic loop; within each set of transmembrane segments are regions of internal symmetry termed alpha(1) and alpha(2) repeats. The central residues that are important for Ca(2+) and K(+) liganding and transport have been identified in NCKX2, and they comprise three central acidic residues, Glu(188) in alpha(1) and Asp(548) and Asp(575) in alpha(2), as well as Ser/Thr residues one-helical turn away from these residues. In this study, we have scanned through more than 100 single-residue substitutions of NCKX2 for shifts in Na(+) affinity using a fluorescence assay to monitor changes in free Ca(2+) in HEK293 cells treated with gramicidin to control intracellular Na(+). We have identified 31 residues that, when substituted, result in shifts in Na(+) affinity, either toward higher or lower K(m) values when compared with wild type NCKX2 (K(m) for Na(+) 58 mm). These residues include the central acidic residues Glu(188), Asp(548), and Asp(575), and their neighboring residues in alpha(1) and alpha(2), in addition to a number of newly investigated residues in transmembrane segment 3. Our results relate the identification of residues important for Na(+) transport in this study to those previously identified as important in the counter-transport of Ca(2+) and K(+), lending support to the alternating access model of transmembrane transport.

Enthalpies of Dilution of l-Alanine in Dimethylsulfoxide + Water and Dimethylformamide + Water Mixtures at 298.15 K

The dilution enthalpies of l-alanine in dimethylsulfoxide (DMSO) + water and dimethylformamide (DMF) + water mixtures at 298.15 K have been determined, respectively, using an isothermal titration calorimeter. On the basis of the McMillan−Mayer theory, the homochiral enthalpic interaction coefficients hXX of l-alanine in both of the mixtures of various mass fractions (w2 = 0 to 0.3) have been calculated. It was found that hXX is positive at lower DMSO or DMF concentrations, but it becomes less positive and even negative with the increasing concentration of DMSO or DMF. The results were interpreted from the point of view of solute−solute interactions mediated by these two aprotic cosolvents.