Dissolution In Tetrahydrofuran Research Articles

An Exceptional Broad-Spectrum Nanobiocide for Multimodal and Synergistic Inactivation of Drug-Resistant Bacteria

An Exceptional Broad-Spectrum Nanobiocide for Multimodal and Synergistic Inactivation of Drug-Resistant Bacteria

Mesostructured natural rubber/in situ formed silica nanocomposites: A simple way to prepare mesoporous silica with hydrophobic properties

We report here a simple way to prepare mesoporous silica materials with hydrophobic properties, as natural rubber (NR)/hexagonal mesoporous silica (HMS) nanocomposites, via an in situ sol-gel process using tetraethyl orthosilicate (TEOS) and decylamine as a silica precursor and organic template, respectively. Effects of swelling the NR sheet in TEOS, prior to dissolution in tetrahydrofuran, on the mesostructure, chemical composition and hydrophobicity of the resulting nanocomposites were investigated. The NR/HMS prepared with the pre-swelling step had superior structural and textural properties to that prepared without the pre-swelling step. The presence of rubber phase entrapped in the mesostructured silica and genuinely mesostructured NR/silica nanocomposite framework was confirmed by osmium tetroxide staining coupled with transmission electron microscopy analysis. The results obtained from X-ray photoelectron spectroscopy indicated a good dispersion of NR molecules in the mesostructured nanocomposites, which was determined by the distribution of non-hydrolyzed ethoxy groups. The use of toluene extraction, followed by characterization of the resulting material, identified the weak nature of the NR-silica interaction. Dynamic light scattering indicated that the presence of TEOS in the pre-swollen NR matrix enhanced the diffusion of template molecules into the rubber phase, and the dispersion of NR molecules in the synthesis mixture. Finally, a plausible mechanism for the formation of NR/HMS nanocomposites via cooperative templating route, in which the remnant ethoxy groups acted as hydrophobic linkers between the rubber chains and the silica oligomers, was proposed.

A rheological method exploiting Cole-Cole plot allows gel quantification in Natural Rubber

Raw Natural Rubber (NR) quality, rather variable, is controlled according to international standards (ISO2000, etc.). Despite these standards, better characterization of this complex material is still needed to reduce feedstock waste and energy losses in the manufacturing processes. Twenty-four NR samples were studied. Their gel contents were quantified after dissolution in tetrahydrofuran. The rheological properties of the raw NR samples were measured in double-shear geometry. The Cole-Cole plot of the shear moduli (G″ = f(G′)) was used to graphically calculate an h parameter, described as an indicator of the crosslink density of a polymer. The total gel of NR was found to clearly influence the rheological properties of the material at low frequency. This study also showed that the microgel of NR accounted for 46–92% of the total gel, and cannot be neglected when investigating the influence of gel on NR properties.

Conversions of zinc cimantrenates in reactions with 1,10-phenanthroline

The reaction between aqueous zinc acetate and cimantrene carboxylic acid has been found to yield Zn[(OOCC5H4)Mn(CO)3] 2[O(H)Me]4, whose dissolution in tetrahydrofuran (THF) gives trinuclear Zn3[μ-(OOCC5H4)Mn(CO)3]4[μ-η2-(OOCC5H4)Mn(CO)3]2(THF)4. Labile THF molecules can be replaced by bidentate 1,10-phenanthroline under mild conditions, thus resulting in Phen2Zn3[μ-(OOCC5H4)Mn(CO)3]4[μ-η2- (OOCC5H4)Mn(CO)3]2. Variations in the reagent ratio and the reaction conditions result in mononuclear PhenZn[(OOCC5H4)Mn(CO)3]2(H2O), which contains a coordinated water molecule. The synthesized complexes have been separated with high yields in the form of single crystals and characterized by chemical analysis, IR spectroscopy, and X-ray diffraction.

Micro/Nano-Structured Polypyrrole Surfaces on Oxidizable Metals as Smart Electroswitchable Coatings

Polypyrrole (PPy) films were electrodeposited from a pyrrole/sodium salicylate solution in water, through two-dimensional (2-D) polystyrene (PS) templates self-assembled on various oxidizable metals, after which the template was removed by dissolution in tetrahydrofuran (THF). The resulting PPy films were analyzed by scanning electron microscopy and atomic force microscopy. Two-dimensional PPy honeycomb structures are obtained on copper or mild steel by using PS spheres of various sizes. The morphology of these structures was controlled electrochemically, as an increase in the polymerization charge does not disturb the PPy honeycomb arrangement, leading instead to the formation of deeper pores accompanied by a change in their diameter. The hydrophobicity of the reduced micro-structured PPy surface is much greater than that of a bulk PPy film generated on the same metal. Reversible electro-switching of the wettability was obtained with marked variation of the apparent contact angle upon PPy oxido-reduction, and an important effect of film micro-structuration upon the wettability range.

Measurement and correlation solubility and mixing properties of dimethyl succinylsuccinate in pure and mixture organic solvents from (278.15 to 333.15) K

The solubilities of dimethyl succinylsuccinate in tetrahydrofuran, acetic ether, acetone, acetonitrile, 1-propanol, ethanol and methanol pure solvents and tetrahydrofuran+methanol mixed solvents were measured within the temperature range 278.15K to 333.15K at atmospheric pressure. The solubility of dimethyl succinylsuccinate in those selected solvents increased with increasing temperature, and the dissolution in tetrahydrofuran is best. The semi-empirical Buchowski–Ksiazczak λh equation, the modified Apelblat equation and CNIBS/R-K equation were used to correlate with the solubility. In pure solvents the values of the sum of deviation (∑(%Dev)) for Apelblat and Buchowski–Ksiazczak λh equations are 1.1115 and 1.0383, respectively. In the tetrahydrofuran and methanol mixture, the sums of deviation (Σ(%Dev)) for Apelblat equation, Buchowski–Ksiazczak λh equation and CNIBS/R-K equation are 0.7587, 0.7059 and 1.4090, respectively. By comparing models, the solubilities predicted by Buchowski–Ksiazczak λh equation and Apelblat equation is reasonable in mixture solvent and pure solvent, respectively. The thermodynamic properties of the solution process, including the enthalpy, and entropy were calculated by the van’t Hoff analysis. The value of enthalpy and entropy were positive.

Structure and Morphology of Charged Graphene Platelets in Solution by Small-Angle Neutron Scattering

Solutions of negatively charged graphene (graphenide) platelets were produced by intercalation of nanographite with liquid potassium-ammonia followed by dissolution in tetrahydrofuran. The structure and morphology of these solutions were then investigated by small-angle neutron scattering. We found that >95 vol % of the solute is present as single-layer graphene sheets. These charged sheets are flat over a length scale of >150 Å in solution and are strongly solvated by a shell of solvent molecules. Atomic force microscopy on drop-coated thin films corroborated the presence of monolayer graphene sheets. Our dissolution method thus offers a significant increase in the monodispersity achievable in graphene solutions.

Electrosynthesis of well-organized nanoporous poly(3,4-ethylenedioxythiophene) by nanosphere lithography

The electrodeposition of poly(3,4-ethylenedioxythiophene) (PEDOT) films from aqueous surfactant solution through a two-dimensional poly(styrene) (PS) template onto indium tin oxide (ITO) substrate has been investigated. The polymer grows in the interstitial spaces of the self-assembled PS spheres which were subsequently removed by dissolution in tetrahydrofuran (THF). Surface characterization by scanning electron microscopy (SEM) and atomic force microscopy (AFM) reveals that two-dimensional nanoporous honeycomb PEDOT structures can easily be obtained by using PS spheres of different sizes. Gold electrodeposition onto the nanostructured PEDOT electrode was investigated and SEM images show preferential formation of nanoparticles (NP) on the wall and the rim of the PEDOT film but metal clusters inside the pores are also observed.

Germanium(II) and Tin(II) Complexes of a Sterically Demanding Phosphanide Ligand

The reaction between PhPCl(2) and 1 equiv of RLi, followed by in situ reduction with LiAlH(4) and an aqueous workup yields the secondary phosphane PhRPH [R = (Me(3)Si)(2)CH]. Treatment of PhRPH with n-BuLi in diethyl ether generates the lithium phosphanide (RPhP)Li(Et(2)O)(n) [15(Et(2)O)], which may be crystallized as the tetrahydrofuran (THF) adduct (RPhP)Li(THF)(3) [15(THF)]. Compound 15(Et(2)O) reacts with 1 equiv of either NaO-tBu or KO-tBu to give the corresponding sodium and potassium phosphanides (RPhP)Na(Et(2)O)(n) (16) and (RPhP)K(Et(2)O)(n) (17), which may be crystallized as the amine adducts [(RPhP)Na(tmeda)](2) [16(tmeda)] and [(RPhP)K(pmdeta)](2) [17(pmdeta)], respectively. The reaction between 2 equiv of 17 and GeCl(2)(1,4-dioxane) gives the dimeric compound [(RPhP)(2)Ge](2).Et(2)O (18.Et(2)O). In contrast, the reaction between 2 equiv of 15 and SnCl(2) preferentially gives the ate complex (RPhP)(3)SnLi(THF) (19) in low yield; 19 is obtained in quantitative yield from the reaction between SnCl(2) and 3 equiv of 15. Crystallization of 19 from n-hexane/THF yields the separated ion pair complex [(RPhP)(3)Sn][Li(THF)(4)] (19a); exposure of 19a to vacuum for short periods leads to complete conversion to 19. Treatment of GeCl(2)(1,4-dioxane) with 3 equiv of 15 yields the contact ion pair (RPhP)(3)GeLi(THF) (20), after crystallization from n-hexane/THF. Compounds 15(THF), 16(tmeda), 17(pmdeta), 18.Et(2)O, 19a, and 20 have been characterized by elemental analyses, multielement NMR spectroscopy, and X-ray crystallography. While 15(THF) is monomeric, both 16(tmeda) and 17(pmdeta) are dimeric in the solid state. The diphosphagermylene 18.Et(2)O adopts a dimeric structure in the solid state with a syn,syn-arrangement of the phosphanide ligands, and this structure appears to be preserved in solution. The ate complex 19a crystallizes as a separated ion pair, whereas the analogous ate complex 20 crystallizes as a discrete molecular species. The structures of 19 and 20 are retained in non-donor solvents, while dissolution in THF yields the separated ion pairs 19a and [(RPhP)(3)Ge][Li(THF)(4)] (20a).

Electrodeposition of macroporous silver films from ionic liquids and assessment of these films in the electrocatalytic reduction of nitrate

Macroporous silver films, ordered or fragmented, were fabricated by electrodeposition of silver into the interstitial spaces of templates formed by polystyrene (PS) latex spheres that had been self-assembled onto bare indium tin oxide (ITO) electrodes or onto gold-coated ITO (ITO/Au) electrodes (in which the electrode had been coated by gold sputtering deposition) from two room-temperature ionic liquids (ILs): N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (BMP-TFSI) and N-butyl-N-methylpyrrolidinium dicyanamide (BMP-DCA), respectively, under normal atmospheric conditions. After electrodeposition of silver, the PS spheres were removed by dissolution in tetrahydrofuran (THF) to leave a macroporous silver structure. The higher wettability of ILs onto PS spheres leads to improved penetration of the ILs into the cavities of the PS templates. Electrodeposition is easier if an electrolyte that has a good penetration into the interstitial spaces between the PS spheres. The macroporous silver electrode exhibited much better electrocatalytic performance with respect to nitrate reduction than a regular silver wire electrode. Quantitative determination of nitrate was also examined.

Synthesis of poly(vinyl alcohol)‐graft‐poly(ε‐caprolactone) and poly(vinyl alcohol)‐graft‐poly(lactide) in melt with magnesium hydride as catalyst

AbstractGrafting of poly(ε‐caprolactone) (PCL) and poly(lactide) (PLA) chains on poly(vinyl alcohol) backbone (PVA degree of hydrolysis 99%) was investigated using MgH2 environmental catalyst and melt‐grown ring‐opening polymerization (ROP) of ε‐caprolactone (CL) and L‐lactide (LA), that avoiding undesirable toxic catalyst and solvent. The ability of MgH2 as catalyst as well as yield of reaction were discussed according to various PVA/CL/MgH2 and PVA/LA/MgH2 ratio. PVA‐g‐PCL and PVA‐g‐PLA were characterized by 1H‐ and 13C‐NMR, DSC, SEC, IR. For graft copolymers easily soluble in tetrahydrofuran (THF) or chloroform, wettability and surface energy of cast film varied in relation with the length and number of hydrophobic chains. Aqueous solution of micelle‐like particles was realized by dissolution in THF then addition of water. Critical micelle concentration (CMC) decreased with hydrophobic chains. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Corrosion protection by polyaniline-coated latex microspheres

The iron plate covered with films of polyaniline-coated polystyrene latex (PANI–PS) microspheres were protected against corrosion in 0.01 mol dm −3 HCl and 3% (w/v) NaCl aqueous solution. PANI–PS particles 1.85 ± 0.06 μm in diameter were synthesized by polymerizing chemically aniline on polystyrene (PS) latex in the suspension. The conducting state (emeraldine salt) of PANI film shifted the corrosion potential of the underlying iron toward a positive from the insulating state of PANI (leucoemeraldine form). The film from which core-polystyrene was removed by dissolution in tetrahydrofuran had the similar anti-corrosive properties. Tafel plots, open circuit potential–time diagrams were used to examine the corrosion properties of PANI–PS coated and uncoated electrodes.

Optical properties of nanostructured metal films.

Nanostructured metal films of platinum, gold and silver up to 675 nm thick we prepared by electrochemical deposition through templates of 700 nm diameter polystyrene spheres assembled as hexagonal close packed monolayer on an evaporated gold surface followed by removal of the template by dissolution in tetrahydrofuran. The reflection spectra of the films at normal incidence were recorded as a function of film thickness and the spectra correlated with the local visual appearance of the film and the surface structure from SEM. For thin films, below one quarter sphere height, the spectra show a single reflectivity dip at a wavelength just below the sphere diameter consistent with surface-plasmon grating-like behaviour. For the thicker films several reflectivity dips are observed which move towards longer wavelength with increasing film thickness. This behaviour is shown to be consistent with a model in which light reflected from the top of the structure interferes with light reflected from within the spherical segment cavities in the film.

Determination of glycolic acid in cosmetic products by solid-phase extraction and reversed-phase ion-pair high-performance liquid chromatography

A procedure has been developed for the assay of glycolic acid in cosmetic products by reversed-phase high-performance liquid chromatography using an ion-pairing method. After dissolution in tetrahydrofuran–water (90:10, v/v), samples were purified by solid-phase extraction using silica-based strong anion-exchange cartridges and analysed directly on an Ultrasphere ODS column with UV detection at 210 nm and methanol–phosphate buffer (2:98, v/v), containing tetrabutylammonium iodide, as the mobile phase. Recovery of glycolic acid from different cosmetic matrices was between 92.4 and 96.2% and the precision of the method was better than 5.4% relative standard deviation. The procedure is rapid, simple, selective and it is suitable for routine analyses of commercial cosmetics.

New polymer syntheses. XC. A-B-A triblock copolymers with hyperbranched polyester A-blocks

Telechelic oligo(ether–ketone)s containing two trimethylsiloxy end groups and one methyl group per repeating unit were prepared by polycondensation of 4-fluoro-2′-methyl-4′-(trimethylsiloxy)benzophenone. The telechelic character was achieved by cocondensation of a small amount of silylated bisphenol-P. The end groups of the silylated oligo(ether–ketone)s were acetylated by means of acetyl chloride. On the basis of 1H-NMR end group analyses two samples of α,ω-bis(acetoxy) oligo(ether–ketone)s with DP = 14 and DP ∼ 28 were obtained. These oligo(ether-ketone)s and a 70 or 140 fold molar amount of silylated 3,5-bis(acetoxy)benzoic acid were polycondensed at 270°C in bulk. The resulting A–B–A triblock copolymers were fractionated by dissolution in tetrahydrofuran. In three out of four experiments a small fraction of precipitated material rich in oligo(ether–ketone) was isolated. The purified triblock copolymers were characterized by inherent viscosities and NMR spectra. For those samples containing the long oligo(ether–ketone) block a low degree of crystallinity was observed after annealing. Four additional polycondensations were conducted with an initial reaction temperature of 290°C. In this way a completely soluble and amorphous triblock copolymer was obtained. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 31–38, 1998

Co-processing of agricultural and biomass waste with coal

The liquefaction of Blind Canyon seam coal in the presence of one of four different types of co-liquefaction agents (CLAs) was studied at 350°C and 1000 psi (cold) hydrogen pressure. The role of tetralin as a solvent was studied. The four CLAs used include sawdust, horse manure, cow manure and commercial “Super Manure”. The conversion and the asphaltene-plus-preasphaltene yield were obtained by successive dissolution in tetrahydrofuran and hexane, respectively, with the oil-plus-gas yield obtained by difference. Results (on a dry, ash-free basis) are reported as both the overall values of conversion and yields, as well as the incremental differences in conversion and yields, relative to separate liquefaction of coal and the CLA. With or without the addition of tetralin, the overall conversion with cow manure is the smallest for the four co-liquefactions. In the absence of tetralin, the asphaltene-plus-preasphaltene yields are all similar. The presence of tetralin increases the overall conversions and the asphaltene-plus-preasphaltene yields. A study of the incremental differences in conversions and yields indicates that the four CLAs interact with coal and tetralin in different ways. The incremental conversion and the asphaltene-plus-preasphaltene yield appear to be related to the amount of hemi-cellulose in the CLAs, while the incremental oil-plus-gas yield appears to be related to the amount of lignin. Added inorganic compounds appear to negate incremental improvements in the oil-plus-gas yield when tetralin is present.

FERROELECTRIC SWITCHING LIQUID CRYSTAL POLYACRYLATES - THE CONTROL AND EFFECT OF MOLECULAR WEIGHT

Abstract The polymerisation of two liquid crystalline acrylate monomers is discussed with particular reference to control of the degree of polymerisation. Two series of liquid crystalline side chain polymers are produced, each with a broad smectic C phase and with a range of molecular weights. The electro-optic behaviour of the materials is discussed, and in one of the series ferroelectric response to electric field is observed for all molecular weights. This includes a sample with a very high degree of polymerisation where the molecular weight is too high to allow dissolution in tetrahydrofuran, and therefore cannot be measured by gel permeation chromatography.

Irreversibility of structural changes induced by stretching in poly(vinyl chloride)

AbstractIt has been shown that certain structural (X‐ray diffraction) and physical (infrared dichroïsm, α‐relaxation dynamics) characteristics of poly(vinyl chloride) undergo irreversible changes upon sample drawing. This behaviour reveals some non‐equilibrium character of the polymer, even in tetrahydrofuran (THF) solution or in the rubbery state (at, typically, glass transition temperature Tg + 10°C). Two tentative ways of explanation have been proposed. The first one would attribute the cause of this peculiar behaviour to physical crosslinks linked to strong interchain bonding. These bonds would resist to dissolution in THF at room temperature but would be broken during stretching. The second way of explanation involves the presence of a metastable GTTG−TT conformation at the end of an isotactic sequence in an mmr chain segment. Like the above mentioned physical crosslinks, it would be transformed upon mechanical loading but not during dissolution in THF or heating to 90°C. Both hypotheses are not necessarily incompatible: as a matter of fact, GTTG− conformations at the end of the isotactic triads could represent sites of especially high intermolecular interaction, distributed along the polymeric chain.

Enhanced stability of potassium solutions in tetrahydrofuran containing 15-crown-5

The process of potassium metal dissolution in tetrahydrofuran containing 15-crown-5 and the properties of the solution were studied. The changes in concentration of potassium anions and electrons as a function of time were determined by means of 39 K NMR and ESR spectroscopie. Enhanced stability of the solution with 15-crown-5 relative to that containing 18-crown-6 or 12-crown-4 was revealed

T-Butylimido complexes of chromium(V). X-Ray crystal structure of t-butylimidotrichlorobis(ethyldiphenylphosphine)chromium(V)

Monoimido complexes of chromium(v) have been obtained by chlorination of CrVI(NBut)2Cl2 to give an oil, ‘Cr(NBut)Cl3,’ which on dissolution in tetrahydrofuran (thf) or dimethoxyethane and crystallising or by interaction with nitrogen or phosphorus ligands gives adducts of stoichiometry Cr(NBut)Cl3L2, e.g. L = thf, quinuclidine, PMe3, etc.; the X-ray structure of Cr(NBut)Cl3(EtPh2P)2 shows the six-coordinate compound to have trans phosphine and mer chloro groups.