OCH CH Research Articles

Short haired wormlike micelles in mixed nonionic fluorocarbon surfactants

We have studied the rheological behavior of viscoelastic wormlike micellar solution in a mixed system of nonionic fluorinated surfactants, perfluoroalkyl sulfonamide ethoxylate, C 8F 17SO 2N(C 3H 7)(CH 2CH 2O) n H abbreviated as C 8F 17EO n ( n = 10 and 20). Above critical micelle concentration, the surfactant, C 8F 17EO 20 forms small spherical micelles in water and the viscosity of the solution remains constant regardless of the shear rate, i.e., the solutions exhibit Newtonian behavior. However, upon successive addition of the C 8F 17EO 10 the viscosity of the solution increases and at certain C 8F 17EO 10 concentration, shear-thinning behavior is observed indicating the formation wormlike micelles. Contrary to what is expected, there is a viscosity increase with the addition of the hydrophilic C 8F 17EO 20 to C 8F 17EO 10 aqueous solutions at certain temperature and concentration, which could be attributed to an increase in rigidity of the surfactant layer and to the shifting of micellar branching to higher temperatures. The oscillatory-shear rheological behavior of the viscoelastic solution can be described by Maxwell model at low frequency. Small-angle X-ray scattering (SAXS) measurements confirmed the formation of small spherical micellar aggregates in the dilute aqueous C 8F 17EO 20 solution. The SAXS data shows the one-dimensional growth on the micellar size with increase in the C 8F 17EO 10 concentration. Thus, the present SAXS data supports the rheological data.

On permittivity and density of the systems (tetraglyme + dimethyl or diethyl carbonate) and the formulation of Δ ε in terms of volume or mole fraction

Relative permittivity and density on mixing from T = 288.15 K to 328.15 K and atmospheric pressure have been measured over the whole composition range for CH 3O(CH 2CH 2O) m CH 3 polyoxyethyleneglycol dimethyl ether with m = 4 (also called 2,5,8,11,14-pentaoxapentadecane or tetraglyme) + (dimethyl or diethyl carbonate). For these systems the deviation of permittivity, Δ ε, changes sign depending on whether it is defined on the basis of mole fractions of volume fractions. Arguments are put forward that support the choice of the definition in terms of mole fraction. The Redlich–Kister equation has been used to estimate the binary fitting parameters and standard deviations from the regression lines were calculated. The density and excess molar volumes were fitted as a function of temperature and mole fraction to a polynomial equation. The temperature dependence of derived magnitudes, such as the isobaric thermal expansion coefficient, α, ∂ V m E ∂ T P , x , and ∂ H m E ∂ P T , x were computed, due to its importance in the study of specific molecular interactions. Different traditional mixing rules have been applied to predict the permittivity of these mixtures.

Lithium ion transport of solid electrolytes based on PEO/CF 3SO 3Li and aluminum carboxylate

A homogeneous, composite polymer electrolyte (PE) containing poly(ethylene oxide) (PEO), CF 3SO 3Li and 33 wt.% of aluminum carboxylate [RC(O)OAlEt 2] 2 with an oligooxyethylene group R = CH 2CH 2C(O)O(CH 2CH 2O) n CH 3 ( n = 7) (AlCarb7), characterized by low glass transition temperature T g = −51.4 °C was prepared. The interaction of aluminum carboxylate with various lithium salts was characterized on the basis of 27Al NMR spectroscopy in CDCl 3 solutions. The bulk conductivity of solid PE with AlCarb7 is of the order of 10 −5 S cm −1 at 60 °C and 10 −4 S cm −1 at 90 °C. Electrochemical tests of Li|PE|Li cells showed a decrease in the R SEI with temperature, stabilizing at about 10 Ω cm −2. The lithium ion transference numbers determined by ac–dc polarization experiments range from 0.7 to 0.9. 7Li, 19F and 1H NMR spectra, the relaxation time and diffusion data were obtained. The calculated lithium transference number t + at 50 °C is equal to 0.995, which suggests practically complete immobilization of the triflate salt anions. In the range of high temperatures (130–180 °C) t + is equal 0.35–0.39. The dependence of t + on temperature should probably be connected with the partial dissociation of the aluminum carboxylate and lithium salt complex.

Rate constants of the reactions of CF 2ClC(O)OCH 3 and CF 2ClC(O)OCH 2CH 3 with OH radicals and Cl atoms at atmospheric pressure

Rate coefficients for the reactions of hydroxyl radicals and chlorine atoms with methyl chlorodifluoroacetate and ethyl chlorodifluoroacetate have been determined at 298 K and atmospheric pressure. The decay of the organics was followed using a gas chromatograph with a flame ionization detector (GC-FID), and the rate constants were determined using a relative rate method with different references. Room temperature rate constants are found to be (in cm 3 molecule −1 s −1): k 1(OH + CF 2ClC(O)OCH 3) = (1.1 ± 0.3) × 10 −13, k 2 (Cl + CF 2ClC(O)OCH 3) = (1.0 ± 0.2) × 10 −13, k 3(OH + CF 2ClC(O)OCH 2CH 3) = (5.4 ± 1.5) × 10 −13 and k 4(Cl + CF 2ClC(O)OCH 2 CH 3) = (1.5 ± 0.3) × 10 −12 with uncertainties representing ±2 σ. This is the first kinetic study of the studied reactions under atmospheric pressure. Free-energy relationships are presented, and halogen substitution in the ester is discussed in terms of reactivity with OH radicals and Cl atoms. On the basis of our kinetic measurements, the tropospheric lifetimes of CF 2ClC(O)OCH 3 and CF 2ClC(O)OCH 2CH 3 are estimated to be around 53 and 11 days, respectively, primarily due to their reaction with hydroxyl radicals in the troposphere.

Monitoring the real time growth of a self-assembled monolayer on a polymer electrolyte surface

The growth of a self-assembled monolayer (SAM) at the surface of a polymer electrolyte has been shown to inhibit the formation of the passivating layer that forms when the polymer is in contact with lithium metal. In this work, ac impedance spectroscopy was used to monitor the formation of SAM layers on polyethylene oxide (PEO) polymer electrolyte thin films as a function of time. To monitor SAM growth, thin PEO films were cast onto interdigitated electrodes. The electrodes were subsequently immersed in a saturated SAM solution and the film impedance was measured. SAM molecules with the general formula: H (CH 2) 32 (CH 2CH 2O) y H ( y = 2, 10, 40) were used. Growth occurred due to interactions with the ethylene oxide portion of the SAM molecules with the PEO surface. To visualize SAM growth impedance data at a single frequency sensitive to changes at the solution interface was plotted verses time. At the point of immersion, a sharp increase in impedance was observed. With time, the rate at which the impedance increased slowed and ultimately leveled off presumably indicating the point at which a nearly complete monolayer had formed. SAM growth was verified using attenuated total reflectance infrared spectroscopy (ATR-IR).

Novel porous film by electroplating with an emulsion of supercritical CO 2

We conducted an electroplating reaction in a constantly agitated ternary system of dense carbon dioxide (CO 2) and electroplating solution with a novel fluorinated surfactant, F(CF(CF 3)CF 2O) 3CF(CF 3)COO(CH 2CH 2O)CH 3. The reaction in the emulsion was investigated as a function of the CO 2 volume fraction and surfactant concentration. With a low surfactant concentration, the nickel film plated in an emulsion composed of less than 20% CO 2 by volume was flat with many pinholes. Electroplating with a 0.09% surfactant concentration in the plating solution by volume formed a smooth film surface free of pinholes. The novel porous film of nickel was fabricated with a 0.12% concentration in the emulsion by volume. Electroplating was found to be possible in an emulsion composed of 40% CO 2 and 60% electroplating solution by volume. Smooth plated films free of pinholes were obtained from the emulsion system in the composition range of 20–40% CO 2 by volume with the novel fluorinated surfactant. With an increase of the surfactant concentration, nickel films with a multi-porous structure were obtained in an emulsion composed of less than 20% CO 2 by volume. This metallic film had a complicated porous structure made up of spheroidal pores of various diameters. We suggested that this novel porous structure could have originated from the emulsion of the electroplating solution and dense CO 2 with the novel fluorinated surfactant. The structure could have been fabricated via the formation of “hard” micelles in the reaction system with a specific surfactant concentration and CO 2 composition. CO 2 in a water micro-emulsion was formed in this reaction system and the dispersion states influenced the novel multiporous structure of the plated film.

New boron compounds as additives for lithium polymer electrolytes

A new class of difluoroalkoxyborane compounds ([R n OBF 2] 2) containing oligooxyethylene groups of various molecular weight in the form of a methyl monoether (R n = CH 3(OCH 2CH 2) n , n = 1, 2, 3 and 7) has been obtained in the reaction of BF 3 etherate with appropriate glycols. 1H, 11B and 19F NMR spectral analysis of the derivatives obtained was carried out and the properties as Lewis acids of these derivatives have been compared with that of corresponding trialkoxyboranes and boron trifluoride in reaction with pyridine. The strength of the interaction of [R 2OBF 2] 2 with the differing in “hardness” anions of various lithium salts has been analyzed on the basis of NMR spectra. The [R n OBF 2] 2 obtained were used as additives for polymer electrolytes containing PEO as polymer matrix and various lithium salts at an equimolar ratio of the boron compound to salt. The highest ionic conductivities, in the order 10 −5 to 10 −4 S cm −1 at 20–70 °C, were achieved for systems containing LiI and LiN(CF 3SO 2) 2. The lithium transference number ( t +) values, determined by the electrochemical method by steady-state technique for LiF and LiCF 3SO 3 are in the 0.6–0.8 range.

Liquid densities and excess molar volumes for (ionic liquids + methanol + water) ternary system at atmospheric pressure and at various temperatures

Excess molar volumes, V m E have been evaluated from density measurements over the entire composition range for ternary liquid system of ionic liquid (1-ethyl-3-methyl-imidazolium diethylenglycol monomethylether sulphate {[EMIM][CH 3(OCH 2CH 2) 2OSO 3]) (1) + methanol (2) + water (3)} at T = (298.15, 303.15, and 313.15) K. A vibrating tube densimeter was used for these measurements at atmospheric pressure. The V m E values were found to be negative at T = (298.15 and 303.15) K. For {[EMIM][CH 3(OCH 2CH 2) 2OSO 3] (1) + methanol (2) + water (3)} at T = 313.15 K the V m E values become positive at higher mole fraction of ionic liquid and at a corresponding decrease in mole fraction of water. All the experimental data were fitted with the Redlich–Kister equation. The results have also been analysed in term of graph theoretical approach.

Effect of copolymer composition, temperature, and carbon dioxide fugacity on pure- and mixed-gas permeability in poly(ethylene glycol)-based materials: Free volume interpretation

Network copolymers, prepared by photopolymerizing poly(ethylene glycol) diacrylate (PEGDA: CH 2 CHCOO(CH 2CH 2O) 14OCCH CH 2) and poly(ethylene glycol) methyl ether acrylate (PEGMEA: CH 2 CHCO(OCH 2CH 2) 8OCH 3), have been studied for mixed-gas CO 2/H 2 and CO 2/CH 4 separations. Gas separation properties in the networks are sensitive to copolymer composition, temperature, and carbon dioxide fugacity in the feed. In conventional approaches, the effect of temperature can be described by the Arrhenius equation, while the influence of copolymer composition and fugacity can only be described empirically; the corresponding models require a large number of adjustable parameters. However, as shown here, the three factors influencing gas transport correlate well with free volume, and a simplified free volume model with only two adjustable parameters can satisfactorily describe the effects of copolymer composition, temperature, and CO 2 fugacity on pure- and mixed-gas transport properties. Copolymer composition and temperature can be directly related to the fractional free volume, while CO 2 fugacity of the feed can be correlated with free volume via the glass transition temperature of the polymer–gas mixture, which is computed using Chow's model.

Adsorption Kinetics of Asymmetric Gemini Surfactants at Air/Water Interface

Asymmetric Gemini surfactants CmH2m+1OCH2CH(OH)CH2N+(CH3)2C8H17Br,referred to as CmOhpNC8(m=10,12 and 14),were synthesized.This type of surfactant molecule has a head region(a hydroxyl and a quaternary ammonium linked by one methylene group)with a small size and two alkyl chains with different lengths.The maximum bubble pressure technique was used to investigate the adsorption kinetics of CmOhpNC8 aqueous solution below their critical micelle concentrations at the air/water interface.The results showed an obvious kinetic process for the adsorption of CmOhpNC8.When CmOhpNC8 were adsorbed on the freshly formed interface,the adsorption process was pure diffusion controlled.When some molecules existed at the interface,the adsorption barrier(Ea)appeared,which reduced with increasing m.This indicated that those molecules with long alkyl chain migrated more easily from the subsurface into the surface,which was attributed to enhanced hydrophobic interaction between the alkyl chains with increasingm.

Organic–inorganic hybrid matrix doped with alkenyldiazenido complexes of molybdenum

New molecular systems based on conjugated groups, trans-[FMo(NNCHCHCHCHCHCH 2CH 3)(Ph 2PCH 2CH 2PPh 2) 2][BPh 4] have been synthesized and characterized. This complex was immobilized in hybrid organic–inorganic matrix obtained by sol–gel. The hybrid matrix of these organically modified silicates, classified as ureasil formed by poly(oxyethylene) chains [POE, (OCH 2CH 2) n ] grafted to siloxane domains by means of urea cross-linkages. All of the new materials were characterized by thermal analysis (DSC), surface analysis (XPS) and spectroscopic methods (FTIR and UV/vis), to gather information on the modifications introduced by the molybdenum complex in hybrid organic–inorganic matrix, as well as on the immobilized complex integrity. The immobilization of the metal complex in the hybrid matrix has kept their integrity, although some distortions can be observed caused by steric effects imposed by the structure of hybrid matrix or/and by interactions between the metal complex and some groups of the hybrid matrix.

Synthesis and structure of titanium alkoxides based on tetraphenyl substituted 2,6-dimethanolpyridine moiety

Novel titanocanes and spirobititanocanes based on 2,6-bis[hydroxy(diphenyl)methyl]pyridine ( 1a) and 2,6-di(hydroxymethyl)pyridine ( 1b) – [2,6-C 5H 3N(CPh 2O) 2]Ti(O- i-Pr) 2 ( 2a), [2,6-C 5H 3N(CPh 2O) 2] 2Ti ( 3a), [2,6-C 5H 3N(CH 2O) 2] 2Ti ( 3b), [2,6-C 5H 3N(CPh 2O) 2]TiCl 2 ( 4) – as well as the closely related N-phenyl derivative PhN(CH 2CH 2O) 2Ti(Cl)Cp ( 5) have been synthesized. Complexes 2– 5 were characterized by 1H and 13C NMR spectroscopy and elemental analysis data. The molecular structure of 3a was determined by X-ray structure analysis.

Redox activity of bimetallic complexes based on tris(3,5-dimethylpyrazolyl)borato molybdenum(II) and tungsten(II) nitrosyls. Complexes derived from ethane-1,2-diol and the crystal structure of anti-[Mo(NO){HB(3,5-Me 2C 3HN 2) 3}(OCH 2CH 2O)] 2 · 4CHCl 3

The bimetallic complexes [{M(NO)(Tp Me2)X} 2(OCH 2CH 2O)] [Tp Me2 = HB(3,5-Me 2C 3HN 2) 3; M = Mo, X = Cl, Br or I; M = W, X = Cl] have been synthesised and characterised spectroscopically and electrochemically. These species can occur as mixture of two diastereoisomers and one of them could be separated following a thermal treatment of the mixture. A direct synthesis of single diastereoisomers (M = Mo, X = I; M = W, X = Cl) is also described. The bimetallic species exhibit two one-electron reduction processes separated by a modest potential difference, Δ E 1/2, ca. 300 mV (M = Mo, X = Cl, Br) indicating an intermediate metal–metal interaction. In the crystal structure of anti-[{Mo(NO)(Tp Me2)(OCH 2CH 2O)} 2] · 4CHCl 3 two nonequivalent dinuclear molecules (point group C 2 h ) are found, with crystallographically identical, doubly bridged {Mo(NO)(Tp Me2)} distorted octahedral units.

Polymer electrolytes based on cross-linked cyclotriphosphazenes

Substituted cyclotriphosphazenes were used to prepare lithium ion conducting polymer networks. Two types of compounds were synthesized starting with the precursor hexachlorocyclotriphosphazene (HCCP): Type I (CVEEP) in which all the chlorine atoms in HCCP were replaced by vinyloxyethoxyethoxy groups (VEE = –OCH 2CH 2OCH 2CH 2OCH CH 2), and type II (CVMEEP) in which half of the chlorine was replaced by VEE and the other half by methoxyethoxyethoxy groups (MEE = –OCH 2CH 2OCH 2CH 2OCH 3). The terminal vinyl groups were used to build up a network by a thermally initiated cross-linking of lithium salt containing membranes. Polymer electrolytes with dissolved LiSO 3CF 3 and LiN(SO 2CF 3) 2 were investigated by impedance measurements. The ionic conductivity of CVMEEP with 10 wt.% LiSO 3CF 3 was 3.2 × 10 − 5 S/cm at 30 °C and 4.1 × 10 − 4 S/cm at 90 °C. Lower conductivity values in the range 10 − 8 –10 − 9 S/cm were obtained at 30 °C for the highly crosslinked CVEEP. An interesting polymer electrolyte with good mechanical properties and a good conductivity of 1.3 × 10 − 5 S/cm (30 °C) was obtained from a solution of MEEP (= poly[bis(methoxy–ethoxy–ethoxy)phosphazene]) and LiSO 3CF 3 in CVEEP as an interpenetrating network.

A new thermoregulated PEG biphasic system and its application for hydroformylation of 1-dodecene

The development of a new thermoregulated polyethylene glycol (PEG) biphasic system composed of PEG-400/1,4-dioxane/ n-heptane is reported in this paper. By applying this system in the hydroformylation of 1-dodecene catalyzed by Rh complexes modified with phosphite ligand containing PEG chains, TMPGP (P[O(CH 2CH 2O) n CH 3] 3, n = 8), the conversion of 1-dodecene and the yield of aldehydes reached up to 96% and 94%, respectively. The catalyst, after being recycled twenty-three times, showed no appreciable loss of catalyst activity. The average Rh loss was 0.65% each run.

Influence of glyme-based nonaqueous electrolyte solutions on electrochemical properties of Si-based anodes for rechargeable lithium cells

Influence of electrolyte solutions on charge–discharge properties of Si-based anodes were examined. As Si-based anodes, electrodes prepared from (i) a mixture of Si and carbon (Si + C) and (ii) a mixture of a Si–SiO 2–C composite and carbon (Si–C + C) were used. As electrolyte solutions, ethylene carbonate (EC)/methylethyl carbonate (MEC)/ n-glyme ternary mixed solvent with 1 M (M: mol L −1) LiPF 6 was used. Poly(ethylene glycol) dimethyl ethers [(CH 3O(CH 2CH 2O) n CH 3, n = 1, 2, 3 and 4)] are generally known as “glymes”. In case of Li/Si + C cells, by mixing glymes to 1 M LiPF 6-EC/MEC (30:70 in mixing volume percentage; EM), discharge capacity tended to become larger than that with EM alone. Cycle life of Li/Si + C cells was approximately the same when different electrolyte solutions were used. Primary reason for the degradation of charge–discharge cycling life of Li/Si + C cells is a physical breakdown and loosing electronic conductive path of Si electrode. This phenomenon was resulted from a large volume change of electrode by expansion and shrinking of Si during charge–discharge of lithium in Si. Also, reactivity of electrolyte solutions toward lithium affected the degradation of charge–discharge capacity. Discharge capacity depended on a reduction potential ( E red) of glymes, not on an electrolyte conductivity ( κ). In case of Li/Si–C + C cells, by mixing n-glymes to EM, the discharge capacity tended to become larger than that with EM alone. Cycling life of Li/Si–C + C cells improved, compared with that of Li/Si + C cells. This was due to a suppression of physical breakdown by Si–C structure with a thin carbon surface layer on it. Influence of reactivity of electrolyte solutions toward lithium on the degradation of charge–discharge capacity of Li/Si–C + C cells was much smaller than that of Li/Si + C cells. Discharge capacity of Li/Si–C + C cells depended on κ, not on Ered.

Novel bent-shaped liquid crystalline compounds: III. Synthesis of Schiff base liquid crystal dimers

A group of new bent-shaped mesomorphic compounds with two identical mesogens (Schiff base), which have 2-hydroxy-1,3-dioxypropylene (–OCH 2CH(OH)CH 2O–) as a short spacer unit, and different lengths of terminal alkoxy chains (–OC n H 2 n+1 ; n = 5–10, 12), are synthesized. Transition temperatures and phase characterization were studied by DSC, POM and XRD analyses. The dependence of phase transition temperatures on the terminal alkoxy chain lengths is discussed. With the increase in the terminal chain lengths, the thermal stability of the smectic mesophases of these liquid crystals was increased, and the smectic–isotropic transition temperatures in this series showed an even–odd effect.

Synthesis and characterization of metallatranes with phenyl substituents in atrane cage

A new series of mono- and diphenylsubstituted silatranes and boratranes N(CH 2CH 2O) 2(CHR 3CR 1R 2O)MZ (M = Si, Z = CH 2Cl, C CPh, H, OMenth, R 1, R 2, R 3 = H, Ph; M = B, Z = nothing, R 1, R 2, R 3 = H, Ph) have been synthesized. Both transalkoxylation and stepwise modification of a preformed metallatrane skeleton were used. The chloromethyl derivatives N(CH 2CH 2O) 2(CHRCHRO)SiCH 2Cl (R = H, Ph) react with tert-BuOK under intramolecular cycle expansion to give 1- tert-butoxy-2-carba-3-oxahomosilatranes N(CH 2CH 2O)(CH 2CH 2OCH 2)(CHRCHRO)SiO t Bu (R = H, Ph). The treatment of boratranes N(CH 2CH 2O) 2(CH 2CR 1R 2O)B (R 1,R 2 = H, Ph) with triflic acid and trimethylsilyl triflate results in the products of electrophilic attack at the nitrogen atom. The molecular structures of four silatranes and one boratrane bearing phenyl groups in the atrane skeleton were determined by the X-ray structure analysis.

The transannular interaction germanium–nitrogen in germocanes: The influence of substituents

The reaction of RN(CH 2CH 2OH)CHR 1CR 2R 3OH ( 1– 8) with a stoichiometric amount of tetrachloro(bromo)germane leads to the corresponding RN(CH 2CH 2O)(CHR 1CR 2R 3O)GeHal 2 ( 9– 21). Difluorenylgermocane 22 was prepared by treatment of diethoxydifluorenylgermane with N-methyldiethanolamine. Different dialkanolamines were found to be successive precursors of dimethylgermocanes, RN(CH 2CH 2O)(CHR 1CR 2R 3O)GeMe 2 ( 23– 26). The chemical properties of simple and easy to access germocanes RN(CH 2CH 2O) 2GeX 2 [X = OH, Br ( 28), Cl ( 29)] were studied and the difluoro ( 27), haloalkoxy ( 30– 32), and dialkoxy ( 33, 34) derivatives were prepared. The structures of the compounds 16, 20– 22, and 26 were confirmed by X-ray diffraction and the structural features in solution of 23 and 26 were studied by NMR spectroscopy (NOEs). The relationship between the nature of substituents at different positions of the germocane skeleton and the strength of the intramolecular Ge ← N bond is discussed.

Synthesis and structure of the tetradeca-iron(III) oxide–alkoxide cluster [Bu 4N] 2[Fe 14O 8(OCH 2CH 3) 20Cl 8

The iron(III) oxide–alkoxide cluster, di-tetra- n-butylammonium octachloro-tetra(μ 3-oxo)-tetra(μ 4-oxo)- icosa(μ 2-ethoxo)-tetradeca-iron(III), has been isolated and its X-ray crystal structure determined.