共查询到20条相似文献,搜索用时 15 毫秒
1.
S. Yamaguchi 《Colloid and polymer science》1999,277(2-3):184-190
The origins of middle surfactant phases (D and Dp′) were investigated in the composition-temperature (49–73 °C) space of a
water/hexaethyleneglycol dodecyl ether (C12EO6)/propanol/heptane system at atmospheric pressure. Two types of three-phase bodies exist in the dilute C12EO6 region of the four-component composition tetrahedron at 49.0 °C. A cone-like three-phase body consisting of aqueous (W),
Dp′, and oil (O) phases becomes thinner with increasing temperature, and collapses into the superimposed critical tie lines
(CTL) at 51.7 °C. One end of the superimposed CTL is a critical double end point where the closed-loop coexistence curve of
the Dp′ and O phases disappears. The chiral three-phase body consisting of W, D, and O phases shrinks with increasing temperature,
and finally vanishes at the tricritical point near 72.5 °C. The roles of C12EO6 and propanol are discussed and the conditions for the middle surfactant phases are discussed on the basis of the whole series
of three-phase behavior.
Received: 9 July 1998 Accepted in revised form: 25 August 1998 相似文献
2.
S. Yamaguchi 《Colloid and polymer science》1998,276(8):715-722
Phase behavior of water/hexaethyleneglycol dodecyl ether (C12EO6)/propanol/heptane system was investigated in a composition–temperature space (25–30 °C) at atmospheric pressure. A cone-like three-phase body consisting of aqueous (W), surfactant (Dp), and oil (O) phases is
formed in the two-phase body of Wm (aqueous micellar phase)+O at 30.0 °C. With decreasing temperature the three-phase body becomes thinner and finally disappears at a critical double end point
(CDEP) where the two critical end points of W and Dp phases are merged. The CDEP exists at about 26.2 °C (T
CDEP). The hydrophile–lipophile balance (HLB) of the mixed amphiphile changes towards lipophilic on addition of propanol. As a
result, the Wm phase separates into two phases W+Dp above the T
CDEP. Further addition reduces the lipophobicity of aqueous media (or the solvophobicity of the mixed amphiphile), and the W and
Dp phases are merged again. Below T
CDEP, since C12EO6 becomes much hydrophilic, the change of HLB lurks and a middle phase (Dp) cannot be observed.
Received: 19 June 1997 Accepted: 20 March 1998 相似文献
3.
S. Yamaguchi 《Colloid and polymer science》1996,274(12):1152-1160
We studied the phase behavior of three coexisting phases in water/propanol/octaethyleneglycol mono dodecyl ether/heptane system at 45°C. A cone-like three-phase body was found in a composition tetrahedron. In the body aqueous and surfactant phases coexist in the presence of the third coexisting phase, an oil phase, with their loci of composition drawing a closed-loop on addition of propanol. The oil phase remains in an oil-rich region without major change in its composition. The roles of propanol are discussed by using hydrophile-lipophile balance and locations of critical tie lines. Propanol mainly plays two roles; one is as a lipophilic cosurfactant and the other is as a water-soluble cosolvent. The compositions of the critical end points were also determined by a method to use the critical tie line as a clue. In other systems the same pattern phase behavior was observed. 相似文献
4.
The conformations of poly(l-glutamic acid) [P(Glu)] in solutions of the bipolar amphiphile 1,20-icosanediylbis(alkylammonium chloride) [C20(RA)2], where RA includes trimethylammonium (TMA), dimethylammonium (DMA), or methylammonium (MA), were investigated with measurements
of the circular dichroism spectra at 10–35 °C. All C20(RA)2 induced an α-helix of P(Glu) in the aqueous solutions. The residue molar ellipticity at 222 nm showed a similar dependence
on the amphiphile concentration (C
s) below 0.5 of the ratio of 2C
s to the residue concentration (C
p) of P(Glu), but it separated into three directions at 2C
s/C
p>0.5. C20(MA)2 induced an α-helix of P(Glu) at 2C
s/C
p<0.5 followed by a helix aggregate at 2C
s/C
p>0.5. C20(DMA)2 and C20(TMA)2 also induced an α-helix, but a helix aggregate. C20(TMA)2 indicated a strong temperature dependence and did not induce a complete α-helix at 35 °C.
Received: 20 June 2001 Accepted: 6 September 2001 相似文献
5.
Three-phase behavior in a mixed nonionic surfactant system 总被引:1,自引:0,他引:1
The effect of monodisperse solubilities of each surfactant in an excess oil phase on the three-phase behavior was investigated in a water/octaethyleneglycol dodecyl ether (R12EO8)/tetraethyleneglycol dodecyl ether (R12EO4)/heptane system. The mid temperature of the three-phase region is defined as the HLB temperature. The HLB temperature is largely skewed to higher temperature in a dilute region due to the difference in the distribution of each surfactant between excess oil and microemulsion (surfactant) phases forming the three-phase body. Taking account of the monodisperse solubilities, the equation for the HLB temperature was obtained on the basis of geometrical calculation of a particular three-phase triangle. The equation well describes the three-phase behavior for a mixed surfactant system in a space of compositions and temperature.In the mixed surfactant system, the monodisperse solubility of R12EO8 in oil phase forming a three-phase body is monotonously increased with the rise in temperature, whereas that of R12EO4 is first increased and then is decreased. Consequently, the sum of both solubilities does not change greatly in a wide range of temperature. 相似文献
6.
《Journal of Dispersion Science and Technology》2013,34(1):119-124
Effect of added oil (heptane or squalane) on the microemulsion structures in polyoxyethylene dodecyl ether (C12EOn) systems was investigated by means of phase behavior and NMR diffusion experiments. In the binary water-C12EOn systems, an isotropic fluid, D2 (or L3), and an aqueous micellar solution, Wm, phases are successively formed with increasing the EO-chain length. Upon addition of heptane, D2 and Wm phases are merged and a microemulsion of large solubilization is produced at a low surfactant concentration. With squalane, the solubilization of oil in D2 phase is very low or almost zero, whereas the oil solubilization in Wm phase is relatively large. These structural changes in microemulsions are discussed based on the self-diffusion coefficients of water, oil, and surfactant measured by the PGSE-NMR method. The difference in the phase behavior may be attributed to the difference in the penetration tendency of oil in the surfactant palisade layer. 相似文献
7.
Jie Cai Jia Guo Minglei Ji Wuli Yang Changchun Wang Shoukuan Fu 《Colloid and polymer science》2007,285(14):1607-1615
Fe3O4/SiO2/poly (N-isopropylacrylamide-co-N,N-dimethylaminoethyl methacrylate) [P(NIPAM-co-DMA)] multiresponsive composite microspheres with core–shell structure were synthesized by template precipitation polymerization.
First, the magnetite nanoparticles were coated with silica and then modified with 3-(trimethoxysilyl)-propyl methacrylate
(MPS). Subsequently, the Fe3O4/SiO2 particles grafted with MPS were used to seed the precipitation copolymerization of NIPAM and DMA. The composite microspheres
with core–shell structure were superparamagnetic, pH-sensitive, and thermoresponsive. The swelling ratio (D25 °C,
pH = 3/D50 °C,
pH = 9)3 coupling of pH and temperature increased up to 21.2, which was much higher than that without comonomer DMA. 相似文献
8.
Raman spectroscopy at 25 °C was performed to analyze speciation in quenched solutions after experiments on sodium tungstates
and sodium tungstate bronze dissolution at t=500 °C, p=1000 bar. The experiments were conducted under different oxidation-reduction conditions in sodium chloride solution media.
The spectra of the quenched solutions were different from those of the reference solutions of 0.02 mol⋅kg−1 W(VI) (H2O) in the pH range 2.3–7.2. Thermodynamic models were established and the fields of predominance of different isopolytungstate
species at 25–50 °C were determined. The experimental results of tungstate dissolution demonstrates that reduced tungstate
solutions may contain a significant amount of tungsten species with valence states lower than W(VI). 相似文献
9.
Hui Du Jianyu He Sicen Wang Langchong He 《Analytical and bioanalytical chemistry》2010,397(5):1947-1953
The dissociation equilibrium constant (K
D) is an important affinity parameter for studying drug–receptor interactions. A vascular smooth muscle (VSM) cell membrane
chromatography (CMC) method was developed for determination of the K
D values for calcium antagonist–L-type calcium channel (L-CC) interactions. VSM cells, by means of primary culture with rat
thoracic aortas, were used for preparation of the cell membrane stationary phase in the VSM/CMC model. All measurements were
performed with spectrophotometric detection (237 nm) at 37 °C. The K
D values obtained using frontal analysis were 3.36 × 10−6 M for nifedipine, 1.34 × 10−6 M for nimodipine, 6.83 × 10−7 M for nitrendipine, 1.23 × 10−7 M for nicardipine, 1.09 × 10−7 M for amlodipine, and 8.51 × 10−8 M for verapamil. This affinity rank order obtained from the VSM/CMC method had a strong positive correlation with that obtained
from radioligand binding assay. The location of the binding region was examined by displacement experiments using nitrendipine
as a mobile-phase additive. It was found that verapamil occupied a class of binding sites on L-CCs different from those occupied
by nitrendipine. In addition, nicardipine, amlodipine, and nitrendipine had direct competition at a single common binding
site. The studies showed that CMC can be applied to the investigation of drug–receptor interactions. 相似文献
10.
Fu Qiang KeNing Sun NaiQing Zhang ShiRu Le XiaoDong Zhu JinHuo Piao 《Journal of Solid State Electrochemistry》2009,13(3):455-467
A-site-deficient perovskite cathode material La0.58Sr0.4Co0.2Fe0.8O3 − δ
(L58SCF) is coated on the yttria-stabilized zirconia electrolyte by screen-printing technique. Several key fabrication parameters
including selection of additives (binder and pore former), effect of coating thickness, sintering temperature and time on
the microstructure, and electrochemical performance of cathode are investigated by scanning electron microscopy and electrochemical
impedance spectroscopy. We study the microstructure and the electrochemical property of the cathode with different kinds of
additives. Results show that the cathode possesses fine microstructure, enough porosity, and ideal electrochemical property
when polyvinyl butyral serves as both binder and pore former in the cathode. The cathode with three screen-printing coats
(thickness 28 ± 7 μm, weight 6.07 ± 0.72 mg cm−2) sintering at 1,000 °C for 2 h shows lower polarization resistance of 0.183 Ω cm2 at 800 °C. Based on the optimized parameters, the polarization resistances of the L58SCF–Ce0.8Gd0.2O1.9 – δ
composite cathode display the R
p values of 0.067 Ω cm2 at 800 °C, 0.106 Ω cm2 at 750 °C, 0.225 Ω cm2 at 700 °C, and 0.550 Ω cm2 at 650 °C. 相似文献
11.
Formation of wormlike micelles (WLMs) in an aqueous mixture of polyoxyethylene cholesteryl ether (ChEOn; where n = 20 and 30) and polyoxyethylene dodecyl ether (C12EOm; where m = 3 and 4) has been reported; rheological and small angle X-ray scattering (SAXS) measurements have been performed in the
micellar solutions of ChEOn as a function of C12EOm for the structural elucidation. When lipophilic cosurfactant, C12EOm is added to the micellar solutions of ChEOn, it favors the sphere-to-cylinder transition due to the penetration of C12EOm in the palisade layer of ChEOn micelle accompanying an increase in viscosity. When the concentration of C12EOm is increased, entangled network of WLMs is formed. A strong shear thinning has been observed in highly viscous samples indicating
the presence of transient networks. Such samples exhibited viscoelastic behavior and could be described by the Maxwell model
with a single stress relaxation mode. A maximum is observed in zero-shear viscosity-C12EOm plot. With further addition of C12EOm, viscosity declines and ultimately a phase separation occurs with the formation of turbid solution of vesicular dispersion.
This decline has been interpreted in terms of micellar branching induced by an increase in endcap energy, E
c (which is compensated by the formation of branch points, having a mean curvature opposite to that of endcaps). The C12EOm induced one-dimensional micellar growth has been confirmed by SAXS. 相似文献
12.
Uniform particles of manganese compounds obtained by forced hydrolysis of manganese(II) acetate 总被引:1,自引:0,他引:1
M. Ocaña 《Colloid and polymer science》2000,278(5):443-449
Procedures for the preparation at low temperature (80 °C) of uniform colloids consisting of Mn3O4 nanoparticles (about 20 nm) or elongated α-MnOOH particles with length less than 2 μm and width 0.4 μm or less, based on
the forced hydrolysis of aqueous manganese(II) acetate solutions in the absence (Mn3O4) or the presence (α-MnOOH) of HCl are described. These solids are only produced under a very restrictive range of reagent
concentrations involving solutions of 0.2–0.4 mol dm−3 manganese(II) acetate for Mn3O4 and of 1.6–2 mol dm−3 Mn(II) and 0.2–0.3 mol dm−3 HCl for α-MnOOH. The role that the acetate anions play in the precipitation of these solids is analyzed. It seems that these
anions promote the oxidation of Mn(II) to Mn(III), which readily hydrolyze causing precipitation. The evolution of the characteristics
of the powders with temperature up to 900 °C is also reported. Thus, Mn3O4 particles transform to Mn2O3 upon calcination at 800 °C; this is accompained by a sintering process. The α-MnOOH sample also experiences several phase
transformations on heating. First, it is oxidized at low temperatures (250–450 °C) giving MnO2 (pyrolusite), which is further reduced to Mn2O3 at 800 °C. After this process the particles still retain their elongated shape.
Received: 19 October 1999 Accepted: 24 November 1999 相似文献
13.
The temperature dependence of the ratios of the rate constants k(C5H10)/k(C6H12) and k(C6H12)/k(C6D12) for the reaction of the cycloalkanes C5H10, C6H12, and C6D12 with OH+ cations in the system (NH4)2S2O8 (0.1 mol/kg)-H2SO4 (94.4 mass %) in the 6–50 °C range has been studied. The activation energies found E(C6H12) − E(C5H10) = − 5.3 ± 0.3 and E(C6D12) − E(C6H12) = 7.9 ± 0.7 (kJ/mol) permits the comparison of OH+ to a group of reagents (NO+2, Pd2+, HSO+3) which interact with the C-H bond via an electrophilic substitution mechanism.
Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 6, pp. 354–358, November–December, 2008. 相似文献
14.
Rabindra N. Roy Lakshmi N. Roy Michael S. Fuge Chandra N. Roy Curtis A. Himes Paul A. Bryant Kyle T. Robinson Daniel A. Kaufmann II Colby H. Grove Toshi Gosh Adonis Bwashi 《Journal of solution chemistry》2009,38(4):471-483
The values of the second dissociation constant, pK
2, and related thermodynamic quantities of [N-(2-acetamido)-2-aminoethanesulfonic acid] (ACES) have already been reported over
the temperature range 5 to 55 °C including 37 °C. This paper reports the pa
H values of four chloride ion free buffer solutions and eight buffer solutions with I=0.16 mol⋅kg−1, matching closely that of the physiological sample. Conventional pa
H values for all twelve buffer solutions from 5 to 55 °C are reported. The residual liquid-junction potential correction for
two widely used temperatures, 25 and 37 °C, has been made. The flowing-junction calomel cell method has been utilized to measure
E
j
, the liquid-junction potential. The operational pH values for four buffer solutions at 25 and 37 °C are calculated using
the physiological phosphate buffer standard based on the NBS/NIST convention. These solutions are recommended as pH standards
in the pH range of 6.8 to 7.2 for physiological fluids. 相似文献
15.
A novel surfactant peptide consisting of an arginine cation with laurate anion has been synthesized, purified and characterized.
The critical micellar concentration (cmc) of peptide in aqueous solutions has been determined using spectroscopic techniques
and is found to increase from 0.06 to 0.11 mM with increasing temperature (15–45 °C). Cmc is also determined in the presence
of salts like NaCl, KCl and sodium acetate and it is found that these electrolytes hinder aggregation with a significant increase
in the case of sodium acetate. The aggregation number of the surfactant peptide has been determined using fluorescence quenching
measurements and is observed to decrease from 14 to 6 with increasing temperature (15–45 °C). The standard free energy change
(ΔG
0
m) and standard enthalpy change (ΔH
0
m) of the peptide aggregate are found to be negative with a small positive value for standard entropy change (ΔS
0
m). The peptide aggregate seems to undergo phase transition above 50 °C as observed from UV–vis and fluorescence spectroscopy.
From pyrene binding studies, it is shown that the interior dielectric constant increases from 5.08 at 34 °C to 8.77 at 50 °C
and further decreases with increase in temperature indicating a phase change at 50 °C. Also, the ratio of excimer intensity
to monomer intensity, which is a measure of microviscosity of the aggregate, decreases with increase in temperature with a
change at 50 °C indicating a phase change.
Received: 14 February 1997 Accepted: 13 August 1997 相似文献
16.
V. B. Balakireva A. V. Kuz’min V. P. Gorelov 《Russian Journal of Electrochemistry》2010,46(7):749-753
Proton and deuteron conductivities in the BaZr1 − x
Y
x
O3 − δ system (x = 0.02–0.2) are investigated experimentally over the temperature range 600–900°C in reducing H2/H2O and D2/D2O atmospheres with pH2O = pD2O = 3.15 kPa. 相似文献
17.
Anushree Purushottam Khandale Shyam Shashibhushan Bhoga 《Journal of Solid State Electrochemistry》2012,16(1):341-352
The solid solubility limit of Ce in Nd2–x
Ce
x
CuO4 ± δ
, prepared by sol–gel process, is established up to x = 0.2. The transition from negative temperature coefficient to positive temperature coefficient, within the solid solubility
region, is observed at 620 °C. The area-specific-resistance (ASR) is optimized for electrochemical cell sintered at 800 °C.
ASR enhances with increase in sintering temperature of cell. ASR value of 0.93 ohm cm2 at 700 °C, determined by electrochemical impedance spectroscopy is comparable against that by voltage versus current (V–I)
characteristics at 0.98 ohm cm2 at the same temperature. Electrochemical performance and ASR of Nd1.8Ce0.2CuO4 ± δ
is improved when prepared by sol–gel route over solid-state reaction, which is attributed to uniform size and shape of nanocrystalline
grains. 相似文献
18.
Sol and Gel state properties of aqueous gelatin solutions of concentrations 4%, 6%, 8% and 10% (w/v) have been investigated
through dielectric relaxation studies done at various temperatures in the range T=20–60 °C carried out over a frequency range f=20 Hz–10 MHz and no relaxation of any nature was observed. The sharp transition observed at the gelation temperature T
gel provided an excellent matching with the same measured through differential scanning calorimetry (DSC). The capacitance (C
p) values above f=100 kHz became increasingly negative as the gel was melted to the sol state. However, in the gel state C
p was found to be almost independent of temperature for frequencies above 100 kHz. At frequencies lower than 10 kHz, C
p measured was ∼105 F, implying pronounced interfacial polarization either due to electro-chemical reaction or because of ions getting trapped
at some interface within the bulk.
Received: 10 February 1997 Accepted: 2 September 1997 相似文献
19.
Krzysztof Miecznikowski James A. Cox Adam Lewera Pawel J. Kulesza 《Journal of Solid State Electrochemistry》2000,4(4):199-204
We describe a sol-gel approach by which iron hexacyanoferrate is immobilized in silica in a manner suited to investigation
by electrochemistry in the absence of a contacting liquid phase. Such physicochemical parameters as concentration of redox
sites (C
o) and apparent (effective) diffusion coefficient (D
app) are estimated by performing cyclic voltammetric and potential step experiments in two time regimes, which are characterized
by linear and spherical diffusional patterns, respectively. Values of D
app and C
o thereby obtained are 2.0 × 10−6 cm2 s−1 and 1.4 × 10−2 mol dm−3. The D
app value is larger than expected for a typical solid redox-conducting material. Analogous measurements done in iron(III) hexacyanoferrate(III)
solutions of comparable concentrations, 1.0 × 10−2 and 5.0 × 10−3 mol dm−3, yield D
app on the level of 5–6 × 10−6 cm2 s−1. Thus, the dynamics of charge propagation in this sol-gel material is almost as high as in the liquid phase. The residual
water in the silica, along with the pore structure, are important to the overall mechanism of charge transport, which apparently
is limited by physical diffusion rather than electron self-exchange. Under conditions of a solid state voltammetric experiment
which utilizes an ultramicroelectrode, encapsulated iron hexacyanoferrate redox centers seem to be in the dispersed colloidal
state rather than in a form of the rigid polymeric film.
Received: 8 April 1999 / Accepted: 13 August 1999 相似文献
20.
The physical–chemical properties and fatty acid composition of sheep subcutaneous, tallow, intestinal, and tail fats were
determined. Sheep fat types contained C16:0, C18:0, and C18:1 as the major components of fatty acid composition (19.56–23.40, 20.77–29.50, 32.07–38.30%, respectively). Differential scanning
calorimetry (DSC) study revealed that two characteristic peaks were detected in both crystallization and melting curves. Major
peaks (T
peak) of tallow and intestinal fats were similar and determined as 31.25–24.69 and 7.44–3.90 °C, respectively, for crystallization
peaks and 15.36–13.44 and 45.98–44.60 °C, respectively, for melting peaks in DSC curves; but those of tail fat (18.29 and
−2.13 °C for crystallization peaks and 6.56 and 33.46 °C for melting peaks) differed remarkably from those of other fat types. 相似文献