Formamide Solution Research Articles

Photochemical synthesis of nano-phase palladium films on quartz

Processes of photochemical deposition of palladium films on quartz from solutions of palladium(II) perchlorate and bis(ethylenediamine)palladium(II) tetraphenylborate in dimethyl formamide solutions and dimethyl formamide-ethanol mixtures were studied. The efficiency of the film deposition increases depending on the solvent nature.

Morphology of potassium chloride in aqueous and in formamide solution — An experimental and computational investigation

The morphology of potassium chloride grown in pure water as well as in water–formamide solution was investigated. Surface morphology of the crystals was examined by using scanning electron microscopy. It has been observed that the potassium chloride crystals are largely grown with {100} face at different concentrations in pure water, which contradicts earlier reports. Experimental results show that the potassium chloride crystals grown in formamide are also cubic in nature. However, it has been found that the sodium chloride crystals are octahedrons under similar conditions. The difference in the morphological behavior of these two alkali halides with formamide was investigated with computational methods. The calculated results revealed that formamide is largely preferred to adsorb on the {111} surface of NaCl, which can lead to octahedrons. However, the energetics is not substantially different for the adsorption of additives to the important surfaces of potassium chloride and results in the formation of a competing stable {100} surface.

Acoustical studies of some derivatives of 1,5-benzodiazepines formamide and tetrahydrofuran solutions at 298.15 K

Some derivatives of 1,5-benzodiazepines have been synthesized and characterized by TLC, IR, NMR, and Mass Spectral data. The ultrasonic velocity, density and viscosity of these synthesized compounds have been measured in dimethyl formamide and tetrahydrofuran at 298.15 K. From these experimental data, various acoustical parameters such as isentropic compressibility, intermolecular free path length, molar compressibility, Rao’s molar sound function, relaxation strength, internal pressure, free volume etc., have been calculated which helps in understanding the molecular interactions occurring in these solutions.

Enthalpies of solution of DL-α-Alanyl- DL-α-Valine in aqueous solution of amides at 298.15 K

The enthalpies of solution of DL-α-Alanyl- DL-α-Valine in aqueous solution of formamide, N-methylformamide, N, N-dimethylformamide, N, N-diethylformamide and N, N-dimethylacetamide were determined by calorimetry at 298.15 K over the concentration range x 2 = 0–0.4 mole fractions. Standard enthalpies of solution Δ sol H m° and transfer Δ tr H m° from water to mixed solvents were computed. The enthalpy coefficients of pairwise DL-α-Alanyl- DL-α-Valine–amide interactions were calculated. The interrelation between the enthalpy characteristics of solution (transfer) of DL-α-Alanyl- DL-α-Valine and the structure and physicochemical characteristics of solvents, as well as the composition of mixtures were revealed.

Nanojets, Electrospray, and Ion Field Evaporation: Molecular Dynamics Simulations and Laboratory Experiments

The energetics, interfacial properties, instabilities, and fragmentation patterns of electrosprays made from formamide salt solutions are investigated in a mass spectrometric vacuum electrospray experiment and using molecular dynamics (MD) simulations. The electrospray source is operated in a Taylor cone-jet mode, with the nanojet that forms being characterized by high surface-normal electric field strengths in the vicinity of 1 V/nm. Mass-to-charge ratios were determined for both positive and negative currents sprayed from NaI-formamide solutions with solute-solvent mole ratios of 1:8.4 and 1:36.9, and from KI-formamide solutions with mole ratios of 1:41 and 1:83. The molecular dynamics simulations were conducted on isolated 10 nm NaI-formamide droplets at mole ratios of 1:8 and 1:16. The droplet was subjected to a uniform electric field with strengths ranging between 0.5 and 1.5 V/nm. Both the experiments and simulations demonstrate a mixed charge emission regime where field-induced desorption of solvated ions and charged droplets occurs. The macroscopic parameters, such as average mass-to-charge ratio and maximum surface-normal field strengths deduced from the simulations are found to be in good agreement with the experimental work and consistent with electrohydrodynamic theory of cone-jets. The observed mass spectrometric Na (+) and I (-) solvated ion distributions are consistent with a thermal evaporation process, and are correctly reproduced by the simulation after incorporation of the different flight times and unimolecular ion dissociation rates in the analysis. Alignment of formamide dipoles and field-induced reorganization of the positive and negative ionic charges in the interfacial region are both found to contribute to the surface-normal field near the points of charge emission. In the simulations the majority of cluster ions are found to be emitted from the tip of the jet rather than from the neck region next to the Taylor cone. This finding is consistent with the experimental energy distributions of the solvated ions which demonstrate that indeed most ions are emitted closer to the jet region, that is, beyond the cone-neck region where ohmic losses occur. This observation is also consistent with continuum electrohydrodynamic predictions of cluster-ion evaporation at surface regions of high curvature and therefore maximum surface electric field strengths, which may be the cone-neck region, the breakup region of the jet (usually near the tip of the jet), or the emitted charged droplets. In the nanoscale jets observed in this study, the regions of highest spatial curvature are at the ends of the jets where nascent drops either are forming or have just detached.

Micellization of bile salts in a formamide solution: A gas liquid chromatography study

Sodium cholate and sodium deoxycholate dissolved in formamide were applied as stationary phases in gas chromatography. The critical micelle concentration of sodium cholate and deoxycholate in formamide was determined by surface tension measurements. The relation of retention times vs. concentration of bile salts was investigated for isomers of monoterpenes and xylenes. The enthalpy of binding of selected compounds with sodium cholate and sodium deoxycholate monomers and micelles was determined.

Enhanced Ferroelectric Phase Content of Polyvinylidene Difluoride Fibers with the Addition of Magnetic Nanoparticles

Polyvinylidene difluoride (PVDF) fibers with continuously dispersed ferrite (Ni 0.5Zn 0.5Fe 2O 4) nanoparticles were prepared by electrospinning from dimethyl formamide (DMF) solutions. The effects of the electrospinning processing conditions and nanoparticle loading on the formation of the alpha, beta, and gamma phases of PVDF were studied using infrared spectroscopy and differential scanning calorimetry. The amount of the ferroelectric beta and gamma phases present in the fibers was found to increase with increased nanoparticle loading. We have shown that the formation of PVDF phases with extended chain conformations can be enhanced by the addition of a well-dispersed nanoparticle phase. At increased nanoparticle loadings, the alpha phase is completely converted to the more extended beta and gamma phases.

Importance of Solution Equilibria in the Directed Assembly of Metal Chalcogenide Mesostructures

We describe the new nanostructured Pt/Ge/Se materials prepared from the molecular units [Ge2Se6](4-) and [GeSe4](4-) and linking Pt(2+) ions in the presence of surfactant micelles. X-ray diffraction coupled with transmission electron microscopy images reveals hexagonal pore symmetry. The solvent dependence and solution speciation of these building blocks were investigated by means of multinuclear NMR spectroscopy and by fast atom bombardment (FAB) mass spectroscopy and it is shown that rapid exchange equilibrium is reached between species like [Ge4Se10](4-), [Ge2Se6](4-), and [GeSe4](4-) in both water and formamide. This results in multiple Ge/Se anions being incorporated in the mesostructured materials which is supported by Raman and IR spectroscopic data. It is likely that the presence of multiple building units both in water and formamide solutions favors the assembly of mesostructured metal chalcogenides with good pore order. Systematic variation of both surfactant headgroup and chain length modulates the optoelectronic properties of the mesostructures. The Pt/Ge/Se materials show sharp band gap transitions in the range of 1.24-1.97 eV. Finally, the materials exhibit reversible ion-exchange properties and a marked inorganic framework flexibility that enables a contraction-expansion process in response to the exchange. The Pt/Ge/Se framework possesses a very high surface area as estimated by small-angle X-ray scattering techniques.

Thermodynamic parameters of solvation of nonelectrolytes in aqueous solutions with hydrogen bond networks

The contributions from interaction and reorganization to the enthaplies of solvation of polar and nonpolar nonelectrolytes in aqueous solutions of formamide, ethanediol, and 1,2-propanediol, forming 3D-associated structures in the entire composition range, were calculated. The enthalpy terms of the solvation of nonelectrolytes in aqueous solutions of methyl-and dimethylformamide were estimated. The data were compared considering the thermodynamic characteristics of these aqueous systems that we determined previously. It was found that the shape of the concentration dependences of the enthalpies of solvation of nonelectrolytes in all the examined solutions is determined by the reorganization term. The fact that the solvation of nonelectrolytes in water is the most exothermic compared to the aqueous-organic systems under consideration is due to the lowest value of the reorganization term in water, despite the fact that nonelectrolytes interact with water more weakly than with the nonaqueous components.

Fluorescence and NIR spectroscopic study on the water interaction in polycarbonate film

Water interactions in polycarbonate films have been studied using fluorescence and NIR Fourier transform spectroscopy. During water sorption process, the fluorescence emission spectra showed sensitive changes with the peak at 332 nm red shifted by 18 nm with water sorption. This red-shifted peak could be due to phenyl-2-phenoxybezoate, which is one of two major thermal degradation products in polycarbonate. In the spectra of phenyl-2-phenoxybenzoate in dimethyl formamide solution, a progressive red shift was also observed with the water addition. By using the NIR spectra, hydrogen-bonding interactions of the sorbed water with polycarbonate were investigated. It was found that water can be analyzed as free water S0 or single hydrogen bonded water, S1 while double hydrogen bonded water was negligible. During water immersion, most water species which are present as S0 species decrease slightly, with a small increase in S1 species. During desorption, S0 species decrease sharply, while S1 species is reduced gradually. Two examples of S1 structure in water-sorbed polycarbonate are proposed.

Recovery, purification, and cloning of high-molecular-weight DNA from soil microorganisms.

We describe here an improved method for isolating, purifying, and cloning DNA from diverse soil microbiota. Soil microorganisms were extracted from soils and embedded and lysed within an agarose plug. Nucleases that copurified with the metagenomic DNA were removed by incubating plugs with a high-salt and -formamide solution. This method was used to construct large-insert soil metagenomic libraries.

Effect of a carbon black surface treatment on the microwave properties of poly(ethylene terephthalate)/carbon black composites

AbstractA surface treatment was applied to carbon black to improve the electrical and microwave properties of poly(ethylene terephthalate) (PET)‐based composites. Three different formamide solutions with 1, 2, and 3 wt % concentrations were prepared to modify the surface chemistry of carbon black. Microwave properties such as the absorption loss, return loss, insertion loss, and dielectric constant were measured in the frequency range of 8–12 GHz (X‐band range). Composites containing formamide‐treated carbon black exhibited enhancements in the electrical conductivity, electromagnetic interference (EMI) shielding effectiveness, and dielectric constant values when compared to composites with untreated carbon black. In addition, increases in the formamide solution concentration and carbon black content of composites resulted in an increase in the electrical conductivity, EMI shielding effectiveness, and dielectric constant values. The percolation threshold concentration of PET composites shifted from a 3 to 1.5 wt % carbon black composition with the surface treatment. The best EMI shielding effectiveness was around 27 dB, which was obtained with the composite containing 8 wt % carbon black treated with a 3 wt % formamide solution. Moreover, this composition gave the lowest electrical resistivity and the highest dielectric constant among the produced composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Structural and thermodynamic parameters and intermolecular interactions in aqueous formic acid amides

The structural and thermodynamic characteristics of aqueous solutions of formamide, N-methylformamide, N,N-dimethylformamide, and N,N-diethylformamide were calculated. The specific and nonspecific components of the total energy of intermolecular interactions were determined. The limits of the concentration regions with differently arranged structures of solutions were established, and the preferable solvation parameters of the solution components were evaluated.

Thermodynamic properties, intermolecular interaction parameters, and structure of aqueous amide solutions of ammonium and tetraalakylammonium bromides

The thermal effects of dissolution of ammonium bromide in water and its mixtures with formamide (FA) at 277–328 K were studied by the calorimetry method in the region of small additions of the nonaqueous component. The standard values of enthalpy and heat capacity of solution, as well as the temperature changes in the solution entropy and reduced dimensionless Gibbs energy, were calculated. The parameters of electrolyte-amide pair interactions were calculated using the McMillan-Mayer formalism. The contributions of the cation and anion to the pair interaction parameters were determined by the group additivity method. The results are compared with the data obtained previously for solutions of tetrabutyl-and tetraethylammonium bromides in aqueous solutions of FA and hexamethylphoshotriamide (HMPT). At elevated temperatures the system becomes less structured in amide solutions of tetraalkylammonium bromides (except solutions of Et4NBr in aqueous HMPT) but more structured in solutions of ammonium bromide and in aqueous FA and HMPT.

Crystallization of Calcium Carbonate Mineral with Hierarchical Structures in DMF Solution under Control of Poly(ethylene glycol)-b-poly(l-glutamic acid): Effects of Crystallization Temperature and Polymer Concentration

CaCO3 superstructures with complex forms and hierarchical surface textures were mineralized in the presence of peptide type block copolymer poly(ethylene glycol)-b-poly(l-glutamic acid) (PEG-b-pGlu) as a crystal growth modifier in dimethyl formamide (DMF) solution. Spindle-like CaCO3 crystals with a rather smooth surface and a size of 10 µm in length and a maximum diameter of 6 µm were mineralized at 24 ± 2 °C. Unique ellipsoid-like CaCO3 particles with many similar thorns distributed on the particle surface formed when the mineralization temperature was kept at 14 ± 2 °C. Complex column-like CaCO3 superstructures comprised of many tiny rods and irregular particles were observed at 4 ± 2 °C. In addition, when the reagent concentration is varied, the morphology of CaCO3 changes from a mixture of spherical and ellipsoidal structures to a kind of complex ellipsoidal superstructure whose surface is attached by many hierarchical tubular structures, and then to a complex columnar structure, when the concentrati...

Effect of Electrospinning on the Ferroelectric Phase Content of Polyvinylidene Difluoride Fibers

Polyvinylidene difluoride (PVDF) fibers were prepared by electrospinning from dimethyl formamide (DMF) solutions. The effects of the electrospinning processing conditions on the formation of the alpha and beta phases of PVDF were studied using infrared spectroscopy and differential scanning calorimetry. We have shown that beta-phase PVDF fibers can be electrospun directly from a dimethyl formamide (DMF) solution with a maximum fraction of beta phase, F(beta)max, of 0.75. The fraction of beta phase is found to be greater for smaller-diameter fibers and those spun at an increased voltage.

Electrospinning of polyvinylidene difluoride-based nanocomposite fibers

Polyvinylidene difluoride fibers and composite fibers with Ni–Zn ferrite nanoparticles and rutile nanoparticles were prepared by electrospinning dimethyl formamide (DMF) solutions. To prevent agglomeration, the ferrite nanoparticles were coated with silica, allowing the formation of a stable ferrofluid in DMF as well as the formation of homogeneous fibers. The rutile nanoparticles could be spun with a uniform distribution within the fiber without silica coating. The effects of various solution properties (viscosity and solids loading for composite fibers) and processing parameters (flow rate and voltage) on fiber morphology and diameter were studied to identify a processing window that resulted in the formation of smooth, defect-free fibers. Of the variables examined, fiber diameter was found to be the most strongly dependent on the viscosity of the electrospinning solution. Infrared spectroscopy revealed that the inclusion of well-dispersed nanoparticles in the electrospun fibers enhanced the presence of the ferroelectric phase in the composite fibers.

Synthesis of tetrazole‐containing azo polymers with properties of photo‐induced birefringence and surface‐relief‐gratings via RAFT polymerization

AbstractA novel optically active monomer, 6‐{4‐[4‐(1‐phenyl‐1H‐tetrazol‐5‐yloxy)‐phenylazo] ‐phenoxy}‐hexyl methacrylate (PTPPHMA) bearing tetrazole and azobenzol moieties, was synthesized and polymerized by reversible addition‐fragmentation chain transfer (RAFT) polymerization using 2‐cyanoprop‐2‐yl dithiobenzoate (CPDB) as the RAFT agent and 2, 2′‐azobis(isobutyronitrile) (AIBN) as the initiator. Well‐defined optically active photochromic polyPTPPHMA(PPTPPHMA) was obtained. “Living”/controlled characteristics were observed in the polymerization: well‐controlled molecular weights (Mns), narrow molecular weight distributions (Mw/Mn) of the polymers and successful chain‐extension of PPTPPHMA with styrene (St) as the second monomer. The photochemical interconversion between trans and cis isomers of PPTPPHMA in N,N′‐dimethyl formamide (DMF) solution was explored under irradiation of ultraviolet light. The photoinduced birefringence on the thin films of PPTPPHMA was investigated. A maximum birefringence of 0.1 was obtained, and no significant change of profiles of the birefringence after several cycles of writing/erasing/rewriting sequences was observed. The surface‐relief‐gratings (SRGs) were induced on the polymer films by interference of Kr+ laser beams at 413.1 nm with 35 mW/cm2 intensity, the diffraction efficiencies from SRGs were measured to be in the range of 2.0–2.5%. The atomic force microscopy (AFM) results showed the gratings produced on the surfaces of the polymer film. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 682–691, 2008

Synthesis of azobenzene-centered (co)polymers via reversible addition-fragmentation chain transfer (RAFT) polymerization

Abstract An azobenzene-based dithiocarbamate, 4,4'-bis[2-(carbazole-N-dithio formatyl)-2-methyl-propionatyl]-azobenzene (CDMPA), was synthesized and used as the chain transfer agent (CTA) for reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene in anisole solution. Well-defined azobenzene-centered and carbazole-ended polystyrene (PS) with well-controlled molecular weight (Mn) and narrow molecular weight distributions (Mw/Mn) was obtained. The good agreement between the theoretical molecular weight (Mn,th) and the 1H NMR determined molecular weight (Mn,NMR) indicated that most of the polymer chains contained an azo-functional center-group end-capped with the carbazole moieties, which were derived from the RAFT agent. The obtained polystyrene (PS) showed a strong ultraviolet absorption in tetrahydrofuran (THF) and emitted fluorescence after excited by UV-irradiation in N,N’-dimethyl formamide (DMF) solutions. The PS was used as the macro-RAFT agent to carry out the polymerization of methyl acrylate (MA) and N-isopropylacrylamide (NIPAAM). Triblock copolymers (PMA-b-PS-b-PMA), and pentablock copolymers (PNIPAAM-b-PMA-b-PS-b-PMA-b-PNIPAAM) were obtained, respectively. These copolymers were characterized by gel permeation chromatography (GPC), FT-IR spectroscopy and NMR spectroscopy.

Testing if the Interstitial Atom,X, of the Nitrogenase Molybdenum−Iron Cofactor Is N or C: ENDOR, ESEEM, and DFT Studies of theS=3/2Resting State in Multiple Environments

A high-resolution (1.16 A) X-ray structure of the nitrogenase molybdenum-iron (MoFe) protein revealed electron density from a single N, O, or C atom (denoted X) inside the central iron prismane ([6Fe]) of the [MoFe7S9:homocitrate] FeMo-cofactor (FeMo-co). We here extend earlier efforts to determine the identity of X through detailed tests of whether X = N or C by interlocking and mutually supportive 9 GHz electron spin echo envelope modulation (ESEEM) and 35 GHz electron-nuclear double resonance (ENDOR) measurements on 14/15N and 12/13C isotopomers of FeMo-co in three environments: (i) incorporated into the native MoFe protein environment; (ii) extracted into N-methyl formamide solution; and (iii) incorporated into the NifX protein, which acts as a chaperone during FeMo-co biosynthesis. These measurements provide powerful evidence that X not equal N/C, unless X in effect is magnetically decoupled from the S = 3/2 electron spin system of resting FeMo-co. They reveal no signals from FeMo-co in any of the three environments that can be assigned to X from either 14/15N or 13C: If X were either element, its maximum observed hyperfine coupling at all fields of measurement is estimated to be A(14/15NX) < 0.07/0.1 MHz, A(13CX) < 0.1 MHz, corresponding to intrinsic couplings of about half these values. In parallel, we have explicitly calculated the hyperfine tensors for X = 14/15N/13C/17O, nuclear quadrupole coupling constant e2qQ for X = 14N, and hyperfine constants for the Fe sites of S = 3/2 FeMo-co using density functional theory (DFT) in conjunction with the broken-symmetry (BS) approach for spin coupling. If X = C/N, then the decoupling required by experiment strongly supports the "BS7" spin coupling of the FeMo-co iron sites, in which a small X hyperfine coupling is the result of a precise balance of spin density contributions from three spin-up and three spin-down (3 upward arrow:3 downward arrow) iron atoms of the [6Fe] prismane "waist" of FeMo-co; this would rule out the "BS6" assignment (4 upward arrow:2 downward arrow for [6Fe]) suggested in earlier calculations. However, even with the BS7 scheme, the hyperfine couplings that would be observed for X near g2 are sufficiently large that they should have been detected: we suggest that the experimental results are compatible with X = N only if aiso(14/15NX) < 0.03-0.07/0.05-0.1 MHz and aiso(13CX) < 0.05-0.1 MHz, compared with calculated values of aiso(14/15NX) = 0.3/0.4 MHz and aiso(13CX) = 1 MHz. However, the DFT uncertainties are large enough that the very small hyperfine couplings required by experiment do not necessarily rule out X = N/C.