Effect of Coagulation Bath DMSO Concentration on the Structure and Properties of Polyacrylonitrile (PAN) Nascent Fibers during Wet-Spinning

Polyacrylonitrile nascent fibers, as spun into the coagulation bath, were prepared by solution polymerization and wet-spinning, and a dimethyl sulphoxide (DMSO)/H ₂ O coagulation bath system was adopted. The effect of coagulation bath DMSO concentration on the structure and properties of the nascent fibers was studied in detail, and the diffusion coefficients of DMSO and H₂O for different bath DMSO concentrations were calculated by Crank's equation to explain the structural changes of the nascent fibers, including cross-section, core/shell structure, and surface morphology. The surface morphology of nascent fibers was observed by field emission scanning electron microscopy (FESEM). The results showed that as the coagulation bath DMSO concentration increased, the diffusion coefficients gradually decreased. More circular cross-section, less core/shell structure, higher degree of crystallinity, larger crystal size, larger bulk density, and higher sound velocity of the nascent fibers were obtained when thecoagulation bath DMSO concentration was 70 wt% compared to lower or higher bath DMSO concentration. Moreover, compared with the nascent fibers spun in other bath DMSO concentrations, smoother surfaces of the nascent fibers were obtained at the bath DMSO concentration of 70 wt%.     

A spectroscopic study of the coordination of dimethyl sulfoxide to a platinum (111) surface

Spectroscopic studies of the adsorption of dimethyl sulfoxide, (CH₃)₂S = O, on Pt(111) have shown that the molecule is bound to the surface via the sulfur atom in an inverted pyramid configuration. A comparison of XPS and EELS data for the adsorbed multilayer and monolayer with XPS and infrared data on the complex PtCl₂(DMSO)₂ is consistent with sulfur bonding. In addition, we detect a considerable increase of the v(S=O) frequency in the DMSO monolayer with decreasing coverage, indicating a coverage dependent heat of adsorption. UPS data show that on adsorption to form a monolayer, the highest occupied molecular orbital of DMSO, presumably the sulfur “lone pair” orbital, shifts to a higher binding energy. These results show a remarkable similarity between DMSO bonding to a metal surface and bonding to a single Pt²⁺ species.     

Improving of the adsorption capacity of halloysite nanotubes intercalated with dimethyl sulfoxide

Algerian halloysite intercalated with dimethyl sulfoxide (DMSO) was prepared. The starting (H) and resulting (H-DMSO) materials were characterized by X-ray powder diffraction, Fourier transformed infrared spectroscopy, thermal analysis, transmission electron microscopy, pore-size distribution analysis, and employed as crystal violet (CV⁺) adsorbents from aqueous solutions. Intercalation reaches a rate of 95% and increases the basal spacing to 11.2 Å. (CH₃)₂SO interacts with the inner surface hydroxyls of halloysite through new hydrogen bonds with the S=O groups. The release of DMSO occurs in two phases: a partial elimination at 195 °C and a second part due to the DMSO combustion at 277 °C. The TEM image of H-DMSO reveals halloysite nanotubes (HNTs) polydisperse in length and diameter. A heterogeneous distribution in the nanotube size was highlighted with pore diameters of 10–11, 20.6, 28.6, and 37.0 nm, in correlation with transmission electron microscopy. The Redlich–Peterson equation describes efficiently the CV⁺ adsorption onto the modified sample. H-DMSO adsorbs 93.6 against 50.9 mg g^?1 for the starting material. This improving of the adsorption capacity of DMSO-intercalated HNTs, was explained via the behavior of the intercalated DMSO molecules. Intercalation constitutes a key procedure for developing new nanocomposites, attractive in technological applications, such as effective adsorbents.     

Raman study of molecular aggregation in liquid dimethyl sulfoxide

Parallel I _∥(ν) and perpendicular I _⊥(ν) polarized components of the S=O band in the Raman spectrum of liquid dimethyl sulfoxide (DMSO) were found to consist of at least three lines each. The depolarization ratios of these lines are different. Only the high-frequency line remains in both components after high dilution of DMSO with CCl₄ 10 mol %. All three lines are present in both components even after high dilution of DMSO with nitromethane, with their intensities being changed only slightly. These facts were explained by the occurrence of various molecular aggregates along with individual (monomeric) molecules present in DMSO and its nitromethane solutions. The monomeric molecules are predominant in a highly diluted CCl₄ solution. The polarized components of the S=O band of an aqueous DMSO solution point to the presence of H-aggregated formations of two types. The similarity in the molecular structure of DMSO and acetone makes it possible to assume that there are aggregated formations in liquid acetone as well. The small difference in wavenumbers as well as the overlap of the lines belonging to various aggregated formations may lead to the noncoincidence of the peaks of unresolved I _∥(ν) and I _⊥(ν) components of the C=O band of acetone.     

Fast etching and metallization of SiC ceramics with copper-vapor-laser radiation

The etching of polycrystalline SiC is studied with the help of radiation of a copper-vapor laser either in air or under the layer of a liquid (H₂O, DMSO). The etching rate in air is as high as 0.24 m/pulse, in DMSO 0.07 gm/pulse at an energy density of 16 J/cm². The etched surface is characterized with Scanning Electron Microscopy (SEM) and X-ray diffractometry. Etching of SiC ceramics in air revealed the partial amorphization of SiC and the formation of microcrystals of elementary Si with an average size of 300 Å. The etched surface of SiC ceramics takes on the ability to reduce Cu from a corresponding electroless plating solution. The adherence of the deposit is as high as 30 N/mm² and is a function of the scanning velocity of the laser beam.     

Microscopic structure of liquid dimethyl sulphoxide and its electrolyte solutions: molecular dynamics simulations

Molecular dynamics (MD) simulations of pure dimethyl sulphoxide (DMSO) and solutions of Na⁺, Ca²⁺, Cl^?, NaCl and CaCl₂ in DMSO have been performed at 298.15 K and 398.15 K in NVT ensembles by using a four-interaction-site model of DMSO and reaction field method for Coulombic interactions. The structure of solvent, ion-solvation shells and ion-pairs have been analysed by employing a concept of coordination centres and characteristic vectors of the solvent molecule. Results are given for atom-atom (corresponding to DMSO), ion-atom and ion-ion radial distribution functions (RDFs), orientation of the DMSO molecules and their geometrical arrangements in the first solvation shells of the ions (Na⁺, Ca²⁺, Cl^?). A preferential formation of cyclic dimers with antiparallel alignment between dipole moments of nearest-neighbour molecules in the pure solvent is found. Geometrical models of the first coordination shells of the ions in ‘infinitely dilute solutions’ are proposed. Ion-ion RDFs in NaCl-DMSO and CaCl₂-DMSO solutions reveal the presence of both solvent separated (SSIP) and contact (CIP) ion pairs. The structures of the solvation shells of such ion pairs are also discussed.     

SOLUTION PROPERTIES OF PACHYMAN FROM PORIA COCOS MYCELIA IN DIMETHYL SULFOXIDE

A linear β-(1→3)-d-glucan PCM3 (pachyman), a major polysaccharide in Poria cocos mycelia, formed aggregates in aqueous solution or dimethyl sulfoxide (DMSO) with absorbed moisture, thereby considerably complicating its fractionation and study of solution properties. In this work, the pachyman PCM3 having narrow polydispersity (M _w/M _n = 1.9) was carefully fractionated by a preparative size exclusion chromatography (SEC) using dehydrated DMSO as the mobile phase. The weight-average molecular mass M _w and intrinsic viscosity [η] of the fractions were measured by static and dynamic laser light scattering, SEC combined with light scattering, and viscometry in DMSO at 25°C, thus eliminating the aggregation. The Mark-Houwink equation for the pachyman in DMSO is established to be: [η] = 6.79 × 10^?4 M _w ^0.95 (mL/g) in the M _w range from 1.2 to 3.5 × 10⁵. The characteristic ratio C _∞ of the PCM3 in DMSO at 25°C, from light scattering by using Flory theory, was obtained to be 10.1, thus indicating that it behaves as a relatively expanded, flexible coil. In addition, the M _w of the pachyman from Poria cocos mycelia was 1.68 × 10⁵, obviously larger than that from the sclerotium (8.9 × 10⁴).     

Quenching of fluorescence for fluoro derivatives of the laser dye DCM in polar solutions

We used fluorescence spectroscopy and nanosecond flash photolysis to study the photophysical properties of the laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylamino)styryl-4H-pyran (DCM) and its two fluoro derivatives: (E)-2-〈2-[2-(4-dimethylaminophenyl)ethenyl]-6-trifluoromethyl-4H-4-pyranylidene〉malononitrile (DCMF3) and (E)-2-〈2-[2-(4-dimethylaminophenyl)ethenyl]-6-n-heptafluoro-propyl-4H-4-pyranylidene〉 malononitrile (DCMF7), in nonpolar n-hexane, mixtures of low-polarity toluene and polar dimethylsulfoxide (DMSO), n-propanol at room temperature and at 77 K. The fluorescence quantum yield Φ_fl of the laser dye DCM increases linearly as the polarity of the binary solvent mixture (toluene+DMSO) increases, from 0.08 in toluene to 0.80 in DMSO. The dependence of Φ_fl on the polarity of the mixture toluene+DMSO for DCMF3 and DCMF7 reaches a maximum for a small amount (∼2 vol.%) of added polar DMSO; and with further increase in the DMSO concentration (≥50 vol.%), the fluorescence of the fluoro derivatives of DCM is practically completely quenched. The quantum yield for intersystem crossing Φ_ST for DCM, DCMF3, and DCMF7 is no greater than 0.01 in solutions of different polarities. We discuss the mechanisms for nonradiative deactivation of the electronic excitation energy for the fluoro derivatives compared with DCM. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 606–612, September–October, 2006.     

Vibrational Spectrum of a Platinum Complex of Piroxicam

The infrared and Raman spectra of a platinum complex of the antiinflammatory drug piroxicam (Pir) and dimethylsulfoxide (DMSO) of composition [PtCl₂Pir(DMSO)] were recorded and briefly discussed on the basis of its structural characteristics. The metal-to-ligand vibrations are analyzed in detail.     

Highly luminescent europium(III) complexes with naphtoiltrifluoroacetone and dimethyl sulphoxide

The synthesis, luminescence properties, experimental determination and theoretical calculation of the emission quantum yield of Eu(NTA)₃.2L complexes, where NTA is naphtoiltri-fluroacetone and L denotes H₂O or DMSO (dimethyl sulphoxide), were reported. The compounds were characterized by elemental analysis (carbon, hydrogen and europium), thermal analysis, UV-visible absorption and photoluminescence spectroscopies. The experimental quantum yields were determined based on a method previously proposed by Bril and collaborators. The Eu(NTA)₃.2DMSO compound shows a high value for the Ω₂ intensity parameter (35.8 × 10^?20 cm²), reflecting the hypersensitive nature of the ⁵D₀ → ⁷F₂ transition and indicating that the lanthanide ion is in a highly polarizable chemical environment. The experimental quantum yield measured for that compound, 0.75, is one of the highest so far reported for solid-state europium complexes. The theoretical calculations of the quantum yield were carried out by solving an appropriate set of rate equations and by using empirical spectroscopic parameters and energy transfer rates. The theoretical results agree well with the experimental data for both complexes. The photostability of Eu(NTA)₃.2DMSO at 358K was evaluated in order to verify whether this complex can be applied as a phosphor for blue light emitting devices.     

Properties of Cellulose Regenerated from Powerful 1-Butyl-3-methylimidazolium Acetate/Dimethyl Sulfoxide Solvent

1-butyl-3-methylimidazolium?acetate C₄mim][CH₃COO]/dimethyl sulfoxide/DMSO can effectively dissolve cellulose at ambient temperature without any heating. However, the thermostability, morphology, and structure of cellulose regenerated from the [C₄mim][CH₃COO]/DMSO solvent is little known. Therefore, in this work, the regenerated cellulose was prepared and characterized by scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and the degree of polymerization (DP) measurements. The results indicated that the regenerated cellulose film displayed homogeneous structures; no chemical reaction occurred between cellulose and [C₄mim][CH₃COO] as well as DMSO during the dissolution and precipitation processes. The regenerated cellulose had good thermal stability, similar to the original cellulose, and the macromolecular chains of cellulose were hardly broken during the dissolution and precipitation processes.     

ESR study of some Cu(II)-4-substituted-2-Thiazolylhydrazone complexes

The Cu(II) complexes with 2-N-acetyl-salicylidene-hydrazino-4-chlor-methyl thiazole (L.) and 2-N-acetyl salicylidene-hydrazioo-4-thiazolyl acetic ester (L_II) were prepared and investigated by ESR measurements. The powder ESR spectrum at room temperature of CuL_IICl is quasi-isotropic (g=2.113), while for CuL_IICl is characteristic of monomeric species with axial symmetry (g _II)=2.234,g ₁=2.073). The isotropic ESR spectra of the CuLCl compounds in DMSO solution suggest the presence of pseudo-tetrahedral monomeric species. The anisotropic spectra were obtained for adsorbed CuLCl DMSO solutions on NaY zeolite. The parallel hyperfine structure shows the coexistence of two magnetic nonequivalent monomeric species. The estimation of some LCAO-MO coefficients using Kivelson and Neiman’s approximation reveals a dominant ionic character for copper-ligand bonds.     

On the possibility of single-electron transfer during alkaline hydrolysis of sulfophthalides

The previously observed generation of radical products during the alkaline hydrolysis of diphenylsulfophthalide (DPSP) and polydiphenylenesulfophthalide in dimethyl sulfoxide (DMSO) is indicative of the involvement of single-electron transfer (SET) in thses processes. The possibility of SET from the hydroxide ion (HI) to the sulfophthalide molecule is determined by the ratio between the ionization potential (IP) of the HI and electron affinity (EA) of the sulfophthalide. According to B3LYP/6-311+G(d,p) calculations for DPSP, EA _ver = 0.06 eV and EA _ad = 0.58 eV, whereas EA _eff = 2.13 eV (with consideration of the C-O bond rupture in the sulfophthalide cycle). Such a value of the electron affinity cannot ensure SET from the HI, the ionization potential of which in DMSO reaches ∼5.25 eV. The EA of the carbocation formed from DPSP is 6.44 eV as calculated in the same approximation. A mode of SET from the HI to the carbocation intermediate formed during DPSP heterolysis in DMSO is proposed. Two possible modifications of the electron donor are considered. The possibility of occurrence of SET from the dimsyl ion and HI-DMSO complex is evaluated using the G3B3 method. The ionization potential of the dimsyl ion in DMSO is almost 1 eV lower than the IP of the HI, which makes the former a preferential donor in comparison with the HI. The ionization potential of the weak HI-DMSO complex even exceeds the IP of the HI; i.e., complexation does not improve the electron-donor properties of the hydroxide ion.     

Photoluminescence of a soluble polypyrrole based on N-vinylpyrrole

Photoluminescence of a novel polypyrrole based on N-vinylpyrrole was systematically observed in organic solutions. The polymer, which has a unique molecular structure, exhibited good photoluminescence in organic solutions. The emission peak of the polymer exhibited one strong green emission band at around 510 nm in common organic solutions. The maximum fluorescence quantum yield of the polymer was found to be 0.16 in NMP solution with fluorescein as standard. At the same concentration, the photoluminescence intensity increased in the order of CHCl₃, THF, DMSO, CH₂Cl₂ and NMP. The photoluminescence spectrum had a slight red shift as the polarity of the solvents increased. The photoluminescence intensity also increased with the polarity of the solvent, except DMSO. This is because of its hygroscopicity in air and its viscosity. In THF solutions, the photoluminescence intensity increased until the concentration reached a certain weight percent (3.0×10⁻² wt.%) and then decreased with higher concentrations. This was most likely due to quenching in the aggregate phase. Furthermore, iron ion was a quencher in the DMSO solution. In a mixed solvent system of DMSO and water, water showed a typical quenching effect.     

Phosphatidylcholine Membrane Fusion Induced by Dimethyl Sulfoxide and Diethyl Sulfoxide

The kinetics of unilamellar vesicle fusion induced by the addition of dimethyl sulfoxide (DMSO) and diethyl sulfoxide (DESO) with mole fractions of 0.1 and 0.2 is studied in the liquid-crystal phase using small-angle neutron scattering. Multilamellar vesicles formed due to the partial fusion of unilamellar vesicles of 1,2-dimyristoyl-sn-glycero-3-phosphadylcholine (DMPC) with the addition of DMSO (Х_DMSO = 0.1, 0.2) and DESO (Х_DESO = 0.2) are stable for a long time. The cooling–heating process does not affect the stability of the formed systems. The presence of DMSO and DESO with a mole fraction of 0.2 leads to disappearance of the ripple phase. The addition of DESO to the unilamellar vesicles of DMPC in D₂O with a mole fraction of 0.1 does not affect the structure of unilamellar vesicles for 5–15 minutes after adding the sulfoxide in the liquid-crystal phase. Three hours later, a stable system consisting of unilamellar vesicles with a lipid bilayer thickness of 27.3(2) Å and multilamellar vesicles with a repeat distance of d = 43.6(2) Å is formed. During cooling, multilamellar vesicles are destroyed in the region of the main phase transition (T'_m = 24.8(9)°C for the investigated system) and unilamellar vesicles are formed.     

Acidities of azoles in the gas phase and in DMSO: an ab initio and DFT study

Acidity of azoles, a very important family of biological molecules with useful pharmacological applications, is examined in the gas phase and in DMSO. The gas phase proton affinities of the corresponding conjugate bases are calculated by the G3 computational scheme and used as a measure of acidity. A good accordance with available experimental data is obtained. It is confirmed that acidity increases with the number of nitrogen atoms in the five-membered ring. The calculated deprotonation energies are interpreted by the triadic formula. It turns out that acidity of azoles is a result of the final state effect and the relaxation energy contribution. It is shown, by using NICS(1) values, that azoles are aromatic compounds and that their aromatic character increases with the number of N atoms. It is also found that aromaticity slightly increases upon deprotonation. Acidity of azoles in DMSO is considered using the isodensity polarized continuum model (IPCM) at the DFT-B3LYP level. A good agreement with accessible experimental results is obtained again. In other cases pK_a values are theoretically predicted and it was found that pentaazole is the most acidic compound with pK_a?=?2. A very good linear relation between theoretical pK_a values and calculated proton affinities of conjugate bases is obtained implying that the trend of changes in the gas phase and in the DMSO solutions is the same.     

Spectroscopic determination of binding between human serum albumin and a platinum(II) dimethylsulfoxide complex

We have used electronic absorption and fluorescence spectroscopy to study binding between a platinum(II) dimethylsulfoxide complex (cis-[Pt(DMSO)₂Cl₂]) and human serum albumin (HSA), and the effect of complexation on the structure of the protein. We have calculated the binding parameters for binding between cis-[Pt(DMSO)₂Cl₂] and HSA. We have determined the binding constant K_B = (1.2 ± 0.1)·10³ M⁻¹ and the Hill coefficient h = 1.03 ± 0.1. We have determined that binding between cis-[Pt(DMSO)₂Cl₂] and the protein leads to a change in the internal packing of the macromolecule. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 573–576, July–August, 2008.     

Abnormal characteristics of binary molecular clusters in DMSO–ethanol mixtures under external electric fields

For the nonlinearly phenomena on the dielectric properties of dimethyl sulfoxide (DMSO)–ethanol mixtures under a low intensity microwave field, we propose a conjecture that there exist some abnormal molecular clusters. To interpret the mechanism of abnormal phenomena and confirm our conjecture about the existence of abnormal molecular clusters, an in-depth investigation about the structure evolutions of (DMSO)_m(C₂H₅OH)_n (m = 0–4; n = 0–4; m + n ≤ 4) molecular clusters induced by external electric fields has been given by using density functional theory. The results show that there exist some binary molecular clusters with large cluster radii in mixtures, and some of them are unstable under exposure of electric fields. It implies that the existence of certain abnormal molecular clusters in DMSO-ethanol mixtures results in their abnormality of dielectric properties.     

Fourier transformation of electron spin-echo modulation: Application to the solvation shell geometry of O2− in dimethyl sulfoxide

The solvation structure of O₂⁻ in deuterated dimethyl sulfoxide (DMSO) was investigated by analyzing the electron spin-echo modulation at 4.2 K. The analysis was carried out by Fourier-transforming the three-pulse echo modulation and by simulating the two-pulse echo modulation. The analysis indicates that each O₂⁻ interacts with two different groups of deuterium nuclei, each group containing six nuclei. It is found by simulating the modulation that one group is located at a distance of 0.25 nm from O₂⁻ with an isotropic coupling of 0.5 MHz while the second group is located at a distance of 0.35 nm with a negligible isotropic coupling. These results suggest a structure with each O₂⁻ solvated by two DMSO molecules arranged asymmetrically about the O₂⁻. The two different distances appear to reflect the solvating molecule orientations with respect to the O₂⁻ bond.     

Study of ion–solvent interactions and activation energy of LiBr in DMSO,H<Subscript>2</Subscript>O and DMSO–H<Subscript>2</Subscript>O mixtures at various temperatures

The Jones–Dole B coefficients of the electrolyte Lithium bromide (LiBr), reference salts tetra butyl ammonium tetra phenyl borate (BU₄NBPh₄), tetra butyl ammonium bromide (BU₄NBr), and potassium chloride (KCl) in dimethylsulfoxide (DMSO), water, and DMSO–water mixtures were obtained at different temperatures range from 25 to 45 °C For this, the relative viscosities were measured for Lithium bromide (LiBr) and reference salts in DMSO, water, and DMSO–water mixtures at above-mentioned temperatures. The B coefficients of these electrolytes were behaved as structure makers in DMSO, while in H₂O and DMSO–H₂O mixtures, the B-coefficient values were less positive showing the weak structure-making effect. Ionic viscosity B coefficients allow us to assess the behavior of ions in the solvent mixtures. In this study it was observed that all the values of ionic B coefficient of (Li⁺) were positive and small showing the weak structure-making effects. It was also observed that Br⁻ ions maintain negative B coefficient values in all DMSO–H₂O mixtures, except in 60% DMSO mole fraction. From this it can be concluded that Br⁻ ion behaved as a structure breaker in water and in all DMSO–H₂O mixtures except in 60% DMSO mole fraction mixtures. The low B _± values of alkali metal ions and Br⁻ ions in water are due to the breakdown of the tetrahedral structural of water and the formation of strongly structured solvated ion. It is also observed that the values of the energy of activation of the flow for LiBr are greater in DMSO–water mixtures and in pure water than in DMSO. This may be due the presence of a network of hydrogen bonds which cause the hindrance in the flow of the solution of LiBr in DMSO–water mixtures and in pure water than in DMSO.