Trace Amounts Of Water Research Articles

Photopolymerization of aniline derivatives in solid state and its application

The photopolymerization of aniline derivatives was investigated in solid state with Flemion film containing Ru(bpy) 3 2+ and PPD (N-phenyl-p-phenylenediamine) in order to form well-defined photo-image. Absorption spectrum indicated that the photopolymerization was succeeded even in a solid state. TG-DTA analysis showed that trace amounts of water (≤ 1 wt.%) remained in the film, suggesting that the trace amounts of water is of important for the photopolymerization in solid state. Consequently, well-defined sub-micropattern was successfully formed by the photopolymerization of aniline derivatives in solid state.

Luminescence spectroscopy of Eu(Bis-tris)3+ complexes in anhydrous DMF [Bis-tris = 2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol]: luminescence quenching rate constants for the 5D0 state of Eu3+ by DMF and polyalcoholic OH groups

Excitation and emission spectra and luminescence lifetimes of Eu3+ complexes obtained by dissolving anhydrous EuCl3 and EuCl3/2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol (Bis-tris) in anhydrous dimethylformamide (DMF) and those from a Eu(Bis-tris)2Cl3 crystalline sample have been studied. Two distinct Eu3+ complexes were observed when anhydrous EuCl3 was dissolved in anhydrous DMF, and one was interpreted as an outer-sphere complex of Cl− anion. Dissolution of an excess amount of vacuum dried NaClO4 or KPF6 in anhydrous DMF resulted in longer luminescence lifetimes, presumably reducing the effects of trace amounts of water in the solvent due to competitive binding of the water in the solvent by alkali metal cations. The quenching rate constant for the 5D0 state of Eu3+ ion by each complexed DMF molecule in solution and by each OH group in the Bis-tris from the Eu(Bis-tris)2Cl3 crystalline sample were 54 ± 1 and 495 ± 5 s−1, respectively, and these were used to interpret the plausible structures of the different Eu3+ complexes in the EuCl3/Bis-tris/DMF solution.

Molecular Weight Characterization of Poly(N-isopropylacrylamide) Prepared by Living Free-Radical Polymerization

A series of relatively monodisperse samples of poly(N-isopropylacrylamide) were synthesized by reversible addition−fragmentation chain transfer (RAFT) over the molecular weight range 2 × 103−3 × 105. For molecular weights below 4 × 104, conditions were found so that polydispersity remained below 1.4 up to high conversion (72%). Molecular weight distributions of polymer obtained using GPC in THF and MALDI were in accord for the low molecular weight range (typically 105). Particular care is required in GPC sample preparation: it is necessary to ensure that trace amounts of water are initially present when drying a polymer sample prior to dissolution in THF, to avoid irreversible chain aggregation. The log/log plot of intrinsic viscosity against molecular weight for polyNIPAM was found to be linear for molecular weights <105, after which the hydrodynamic volume seems to be independent of molecular weight. The Mark−Houwink parameters obtained from the lower molecular weight data are K = 10-(4.24±0.42) dL g-1 and a = 0.78 ± 0.09.

Polar organic phase liquid chromatography with packed capillary columns using a vancomycin chiral stationary phase

Vancomycin immobilized on silica served as the chiral stationary phase (CSP) in this investigation with polar organic solvents as the mobile phase in liquid chromatography (LC). It was shown that trace amounts of water were beneficial for improving peak shape and efficiency. To regulate the retention and selectivity an acid and/or base were added to the mobile phase where an excess of acid was shown to be preferential for enantioseparation. An unusual increase in selectivity with increasing temperature was shown for the acidic drug, thalidomide. Additionally, nonlinear van't Hoff plots were obtained for metoprolol enantiomers that showed increased retention with increasing temperature. Metoprolol also showed unusual behavior in the polar organic phase when water was added to resemble reversed-phase chromatography, with minimum retention observed at high water or high methanol concentrations. In both instances a high degree of electrostatic interaction between metoprolol and vancomycin was concluded. Metoprolol and ten of its analogs were examined on this CSP to evaluate the enantiorecognition process. A comparison in enantioselectivity for a number of acidic and basic drugs using this CSP was also carried out using the polar organic phase, reversed phase, and normal phase LC which were all compared to the results obtained in supercritical fluid chromatography (SFC). Polar organic phase LC offered a better separation of basic molecules while reversed phase LC was preferred for the resolution of acids. SFC showed the broadest enantioselectivity overall and normal phase LC indicated similar properties, as expected, to SFC but with lower column efficiency. Copyright 2000 Wiley-Liss, Inc.

Dehydration of Glycerol–Water Mixtures Using Pervaporation: Influence of Process Parameters

Pervaporation, a membrane-based separation technique, is proposed as a potential replacement for the vacuum distillation process which is normally used for the dehydration of glycerol-water mixtures. Separation characteristics of glycerol-water mixtures containing a trace amount of water by using a water-selective cellophane membrane are studied. Experiments show that the membrane is selective toward water, and pure water is obtained as the permeant. Thus, the selectivity coefficient is infinite. However, the rate of permeation of water is solely controlled by the liquid-phase mass transfer boundary layer resistance due to the very high viscosity of glycerol. Accordingly, increased agitation and temperature cause considerable enhancement of flux. On the other hand, the presence of salt in the feed mixture significantly reduces the rate of permeation. An unsteady-state model, that includes various process parameters, has been developed for prediction of the process output. The model prediction fits satisfactorily with the experimental observations of the present study.

Syntheses and characterization of mixed acetylacetonate–catecholate complexes of zirconium, [Zr3(acac)4(cat)4(MeOH)2], [Zr(acac)2(DBcat)]2 (H2DBcat = 3,5-di-tert-butylcatechol) and [Zr4(μ4-O)(acac)4(DBcat)3(OMe)4(MeOH)

Reactions of the acetylacetonate complex [Zr(acac)4] with catechols have been investigated. Two crystalline complexes [Zr3(acac)4(cat)4(MeOH)2] 1 and [Zr(acac)2(DBcat)]22 (H2DBcat = 3,5-di-tert-butylcatechol) are isolated from the respective reactions in toluene, and their solid-state structures established by X-ray diffraction studies. Complex 2 consists of an edge-shared capped trigonal prismatic structure involving two symmetry related [Zr(acac)2(DBcat)] units, while 1 is best visualized as a Zr3 complex, possessing two [Zr(acac)2(cat)(MeOH)] units linked to the central [Zr(cat)2] fragment via four bridging catecholate ligands. Their reactivity was investigated; treatment of 2 with a trace amount of water in a solution of methanol and CH2Cl2 gave a Zr4 oxo complex [Zr4(μ4-O)(acac)4(DBcat)3(OMe)4(MeOH)] 3.

Spontaneous Formation of Reverse Vesicles with Soybean Phosphatidyl Ethanolamine in Mixture with Triglyceride and Some Water

Mixing the phospholipid soybean phosphatidyl ethanolamine (PE) with the triglyceride triolein and a trace amount of water leads to a spontaneous formation of isotropic aggregates. Evidence for the existence of such aggregates in pseudo-three-component systems is presented here for the first time. Dynamic light scattering and cryogenic temperature transmission electron microscopy reveal polydisperse spherical particles with radii in the range of 250−840 nm and a mean radius of the order 600 nm. From the results of both depolarized light scattering and time-resolved electro-optical birefringence (Kerr effect) the presence of aggregates with an optical anisotropy (rodlike or wormlike reverse micelles as well as particles with lamellar structure) can be excluded. The remaining possibilities are reverse vesicles and a dispersed cubic bicontinuous phase, where our results favor reverse vesicles. A necessary condition for the formation of reverse vesicles is a saturation of the PE−triolein mixture with water; at...

VOQ2OH OR [VOQ2-O-VOQ2] (Q = 8-HYDROXYQUINOLINATE)? A CLASSIC MONOMER-DIMER DILEMMA REVISITED

The electrochemical behavior of VOQ2OH or [VOQ2-OVOQ2] (Q = 8-hydroxyquinohnate anion) has been investigated by cyclic voltammetry in acetonitnie solutions. Although both species exist simultaneously at every condition analyzed, they can be clearly differentiated by this method. The effect of trace amounts of water on the electrochemical behavior is also discussed.

Characterization of Lecithin Cylindrical Micelles in Dilute Solution

An extensive study of the polymerlike properties in dilute solutions of lecithin cylindrical micelles, with trace amounts of water, in isooctane is presented. In contrast to the current picture that this system behaves as a solution of wormlike polymers, we find that it is best described as a solution of rodlike micelles. This finding is based on the combined results of viscometry, electrooptic birefringence, dielectric spectroscopy, static and dynamic light scattering, and dynamic sedimentation. Also, the size of the micelles seems to be independent of the concentration, whereas a strong dependence is predicted for polymerlike micelles. There is a rather abrupt change in micellar size at low concentration, which can be attributed to a sphere-to-rod transition. At high water content further evidence is found for the percolation of the micelles into a connected network, as has been suggested by us recently.8

Removal of perylene from water using block copolymer nanospheres or micelles

Water-soluble nanospheres with poly(acrylic acid) (PAA) coronas were prepared from poly(2-cinnamoylethyl methacrylate)-block-PAA (PCEMA-b-PAA) and P(CEMA-ran-OEMA)-b-PAA, where ran denotes the random incorporation of 2-octanoylethyl methacrylate (OEMA) into the PCEMA block. These nanospheres and polystyrene-block-PAA micelles uptake perylene, a polycyclic aromatic hydrocarbon (PAH), from water. The nanospheres or micelles, with the sorbed perylene, are precipitated by CaCl 2 . These nanospheres may be useful in concentrating PAHs present in trace amounts in water for chemical analysis or in the reclamation of water contaminated by PAHs. Investigated in this article are factors that govern the capacities of the nanospheres and micelles, and the critical calcium concentration for inducing nanosphere or micelle precipitation.

Optimization and Mechanistic Analysis of Oligonucleotide Cleavage from Palladium-Labile Solid-Phase Synthesis Supports1

Pd(0)-labile solid-phase synthesis supports have been used to produce oligonucleotides containing 3‘-alkyl carboxylic acid and 3‘-hydroxy termini in quantitative yields. Optimization of the cleavage reaction conditions using tetrabutylammonium formate buffer resulted in quantitative yields of oligonucleotides using 4 molar equiv of Pd2(dba)3·CHCl3 in 1 h at 55 °C. A proton source facilitates cleavage of the oligonucleotide from the supports. Trace amounts of water, acting as a nucleophile on the η3-complex, presumably preventing back biting by the initially released oligonucleotide, are required to obtain reproducibly high yields of cleaved oligonucleotides during a 1 h reaction. The previously observed lability of β-cyanoethyl groups to the Pd(0) conditions has been examined using a mononucleotide substrate. Cleavage of the β-cyanoethyl group was shown to proceed to the exclusion of other alkyl groups. A mechanism involving initial insertion by Pd(0) into the carbon−oxygen bond of the β-cyanoethyl group is suggested to account for the cleavage of this group.

High‐temperature creep of partially molten plagioclase aggregates

We have investigated the high‐temperature creep of synthetic labradorite (An60Ab40) between 1323 K and 1523 K at atmospheric pressure and low stresses (2–65 MPa). Average grain size varies from 12 to 16 μm. Samples contained up to 12 vol % melt (An60Ab40 glass). Fourier transform infrared measurements indicate that trace amounts of water (∼0.1–0.15 wt % H2O) were incorporated during crystallization. This water was only partly released at high temperature and atmospheric pressure. At low stresses and temperatures, deformation of labradorite was controlled by grain boundary diffusion creep yielding a stress exponent of n∼1 and an activation energy of 365±25 kJ/mol (regime I). With increasing stress and temperature, mechanical data and microstructural observations indicate a transition to power law creep with n∼3 (regime II). This transition occurs in both partially molten and melt‐free aggregates. In regime I the strain rate of samples containing as much as 12 vol % melt is between 3 and 5 times higher than in fully crystalline specimens. The activation energy is only slightly affected by the melt content between 0 and 10±2 vol %. Transmission electron microscopy shows that the amorphous phase resides in connected triple junctions or in unconnected pockets. Grain boundaries are not wetted except surrounding large melt pockets. The melt distribution of undeformed and deformed samples is similar. The strength and activation energy of synthetic labradorite are comparable to those for pure anorthite with trace amounts of water. Both plagioclase compositions are slightly weaker than synthetic diopside.

Water-Soluble Poly(2-cinnamoylethyl methacrylate)-block-poly(acrylic acid) Nanospheres as Traps for Perylene

Poly(2-cinnamoylethyl methacrylate)-block-poly(acrylic acid) (PCEMA-b-PAA) nanospheres are soluble in water. The lightly cross-linked PCEMA cores of these nanospheres can uptake perylene, a polycyclic aromatic hydrocarbon (PAH), from water. Reported are the rate of perylene incorporation into the nanosphere cores and the coefficient of perylene partition between the cores and water. Also the nanospheres were shown to precipitate completely with the addition of sufficient divalent cations such as Ca2+ and redisperse with EDTA which complexes with Ca2+. These nanospheres should be useful in concentrating PAHs present in trace amounts in water for chemical analysis or in the reclamation of waters contaminated by PAHs.

Role of conformation and orientation of surfactants and polymers in controlling flocculation and dispersion of aqueous and non-aqueous suspensions

Flocculation and dispersion of both aqueous and non-aqueous suspensions using surfactants and polymers have widespread applications. In this work, the role of adsorbed layer microstructural properties, namely their conformation and orientation at the solid-liquid interface, in controlling dispersion properties is examined. A multi-pronged approach, involving the use of fluorescence and ESR techniques along with measurements of surface charge and hydrophobicity, was used to explore the structure of the adsorbed layer. The adsorption isotherm of sodium dodecylsulfate on alumina in aqueous solution interface showed different regions corresponding to different adsorption mechanisms. The suspension stability also displayed significant changes concomitant with changes in the structure of the adsorbed layer. When polymers are used their conformation can be manipulated by changing solution conditions such as pH and/or by the addition of a secondary polymer or surfactant. Such manipulation can be used to obtain desired levels of flocculation or stabilization. In non-aqueous media, adsorption was found to depend on the solid-solvent-solute interactions as expressed by an effective interaction parameter δ eff. The suspension stability was dependent on the amount adsorbed and the packing of molecules in the adsorbed layer. The presence of even trace polar impurities was found to have a critical effect on the suspension stability. For example, trace amounts of water were found to cause a significant enhancement of stabilization of alumina cyclohexane suspension in the presence of adsorbed surfactant layers. However, at higher concentrations water induced rapid flocculation in these systems. Hydrophobic polymers were found to be effective stabilizers for alumina in both aqueous and non-aqueous media. In this case the polymer adsorbed at the interface in different orientations with the lyophilic side chains dangling into the solution to provide steric repulsion and thus stabilization.

Process development for electrocarboxylationof 2-acetyl-6-methoxynaphthalene

Electrochemical carboxylation of 2-acetyl-6-methoxynaphthalene to 2-hydroxy-2-(6-methoxy-2-naphthyl)propionic acid may be carried out in good yield (∼89% in the electrolysis; 75% as isolated dried product) in an undivided flow cell using lead as the cathode and aluminium as the dissolving anode. Dimethylformamide was found to be the best solvent for the reaction and low cost tetraethylammonium chloride hydrate is a good electrolyte for the system. The best conditions are those that increase carbon dioxide concentration although higher pressure seems to be more effective than low temperature. The reaction may be carried out with good yield at fairly high current density (1150Am−1) and higher current densities are likely attainable. The allowable payload is limited to around 10% because higher payloads (20%) resulted in solution too viscous to pump. Initially it was surmised that trace quantities of water would be detrimental to good yields in these reactions. However, it was found that small amounts of water (that associated with typical quaternary ammonium chloride salts) has the beneficial effect of eliminating the major byproduct which is formed in more nearly anhydrous solutions without resulting in formation of alternative byproducts. Process conditions were evaluated at 0.2L scale, then scaled up to 1L and finally 75L. The best results were attained in the 1L system, solvable operating problems limited the yield in the largest scale electrolysis.

Static structure factor of polymerlike micelles: Overall dimension, flexibility, and local properties of lecithin reverse micelles in deuterated isooctane

We report a systematic investigation of the static structure factor $S(q,c)$ of polymerlike reverse micelles formed by soybean lecithin and trace amounts of water in deuterated isooctane using small-angle neutron scattering and static light scattering. The experimental data for different concentrations in the dilute and semidilute regime cover approximately three decades of scattering vectors. The data have been analyzed using polymer renormalization-group theory and a nonlinear least-squares fitting procedure based upon a numerical expression for the single chain scattering function of a wormlike chain with excluded-volume effects. Furthermore, the influence of interaction effects on the static structure factor have been successfully examined within a modified random-phase approximation. Additional information on the local scale has been extracted by applying indirect Fourier transformation and square-root deconvolution techniques. We demonstrate that we can determine structural properties such as the micellar cross-section profile and flexibility as well as quantitatively incorporate the influence of micellar growth and excluded-volume effects on $S(q,c).$

A key technology to improve the cyclic performances of carbonaceous materials for lithium secondary battery anodes

Any carbonaceous material does not necessarily provide a favorable surface fora smooth electrochemical lithium doping/undoping reaction because the carbon surface is covered with a very thin inhibiting surface layer. Especially, carbonaceous materials prepared at lower temperatures exhibit very poor charge/discharge cycleability. Removing such a surface layer was found quite effective to provide very favorable electrode surfaces for the doping/undoping reaction. Simple heating of the pristine sample in vacuum was effective, but a more effective and versatile method was a mild oxidation treatment at a moderate temperature only for several minutes. Upon being treated with the mild oxidation, the cycleability as well as high rate capacity of carbonaceous materials were improved to a great extent. A trace amount of water contained in nonaqueous electrolyte was also found to deteriorate the electrochemical properties, which was ascribed to the formation of retarding surface film such as LiOH through the reduction reaction with lithium cation and water during charging.

Structure and flexibility of worm-like micelles

Small-angle neutron scattering and static light scattering experiments have been performed on worm-like micelles formed by soybean lecithin and trace amounts of water in deuterated iso-octane. The structure and flexibility of the aggregates have been investigated as a function of solution composition. The data analysis comprises an application from results of conformation space renormalization group theory and a non-linear least-squares fitting procedure based upon a recently developed numerical expression for the scattering function of a worm-like chain with excluded volume effects.

Nucleophile-Assisted Cleavage of Benzyltrialkylsilane Cation Radicals

The cation radicals of benzyltrialkylsilanes have been generated using photoinduced electron transfer and characterized using transient absorption spectroscopy. Absolute rate constants for nucleophile-assisted C−Si bond cleavage have been determined, for different nucleophiles in different solvents and with different substituents on the phenyl ring. The short lifetime (<10-9 s) of the parent benzyltrimethylsilane cation radical in acetonitrile was unambiguously shown to be due to a rapid nucleophile-assisted bond cleavage, with the solvent acting as the nucleophile. Even in less polar solvents, such as dichloromethane, the lifetime of benzyltrimethylsilane cation radical is quite short (ca. 20 ns) unless trace amounts of water, which acts as an efficient nucleophile, are removed. Consistent with the nucleophile-assisted cleavage mechanism for the benzyltrialkylsilanes, sterically-demanding substituents on silicon decrease the rate constant for cleavage by as much as 4 orders of magnitude, depending upon the nucleophile. Similarly, increasing steric crowding on the nucleophile also decreases the rate constant, although smaller changes in the rate constants are observed. Electron-donating substituents (4-methyl and 4-methoxy) on the phenyl group also lead to a substantial decrease in the rate constant for cleavage of the cation radicals. When measurements are performed in the least nucleophilic solvent and under conditions that minimize contributions from adventitious nucleophiles, the lifetimes of the cation radicals of the benzyltrialkylsilanes can be so long that the rate of pseudo-first-order decay can not be accurately determined. If the cation radicals undergo unimolecular C−Si bond cleavage (i.e., not nucleophile-assisted) under these conditions, the rate constant for this process is estimated to be less than 104 s-1.

Interaction between macroparticles in a simple model system of a nonpolar liquid containing trace amounts of water

We report results of numerical analyses on the macroparticle interactions immersed in a simple model system of nonpolar liquid containing trace amounts of water. The singlet Ornstein–Zernike approach with the reference hypernetted-chain closures is employed. Particles of component 1 (water) are characterized by strong attractive interaction among them, those of component 2 (nonpolar liquid) are hard spheres, and particles of different components interact through hard-sphere potential. The mole fraction of component 1 x1 is very small. Beyond x1=x1P, the mixture cannot exist, even in the metastable state with a single phase. Some affinity is considered only between the macroparticle surface and component 1. When the affinity ξ (negative ξ implies repulsion) is increased with fixing x1 (at a value significantly smaller than x1P) and the macroparticle diameter dM, the macroparticle interaction φMM shifts to the lower (more attractive) side and eventually becomes extremely long-ranged and divergent. For larger x1, the divergence occurs at lower ξ. Whenever φMM becomes divergent, the reduced density profile of component 1 near the surface also becomes extremely long-ranged and divergent. The effects of dM on φMM is also analyzed. At the stability limit (x1→x1P), the divergences occur irrespective of ξ and dM, which is consistent with the recent prediction [Attard et al., Phys. Rev. A 45, 7621 (1992)].