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1.
Bojan Šarac Janez Cerkovnik Bernard Ancian Guillaume Mériguet Gaëlle M. Roger Serge Durand-Vidal Marija Bešter-Rogač 《Colloid and polymer science》2011,289(14):1597-1607
The complex aggregation processes of dodecyltrimethylammonium chloride (DTAC) have been studied in dilute solutions of sodium
salicylate (NaSal) by isothermal titration calorimetry and electrical conductivity at temperatures between 278.15 K and 318.15 K.
A structural transformation that was dependent on the concentrations of DTAC and NaSal was observed. The micellization process
in dilute solutions of DTAC has been subjected to a detailed thermodynamic analysis and shown to occur at considerably lower
critical micelle concentrations than reported for DTAC in water and NaCl solutions. Gibbs free energy, Δ
mic
G
o, and entropy, Δ
mic
S
o, were deduced by taking into account the degree of micelle ionization, β, estimated from conductivity measurements. From the temperature dependence of the enthalpy of micellization, Δ
mic
H
o, the heat capacities of micellization, Dmic cpo {\Delta_{{{\rm mic} }}}c_p^o were determined and discussed in terms of the removal of large areas of non-polar surface from contact with water upon micellization.
The process is exothermic at all temperatures, indicating, in addition to the hydrophobic effect, the presence of strong interactions
between surfactant and salicylate ions. These were confirmed by 1H NMR spectroscopy and diffusion NMR experiments. Salicylate ions not only interact with the headgroups but also insert further
into the micelle core. At c
NaSal/c
DTAC > 2.5, the structural rearrangements occur even at relatively low concentrations of NaSal. 相似文献
2.
M. Fujiwara T. Okano T. -H. Nakashima A. A. Nakamura G. Sugihara 《Colloid and polymer science》1997,275(5):474-479
For a sodium salt of α-sulfonatomyristic acid methyl ester (14SFNa), one of the α-SFMe series surfactants, critical micellization
concentration (CMC), solubility and degree of counterion binding (β) were determined by means of electrocon-ductivity measurements
at different temperatures (at every 5 °C) ranging from 15 to 50 °C. The phase diagram of 14SFNa in pure water was constructed
from the CMC- and solubility-temperature data, in which the Krafft temperature (critical solution temperature) was found around
0 °C. The changes in the Gibbs energy, ΔG
0
m, enthalpy, ΔH
0
m, and entropy, ΔS
0
m, upon micelle formation as a function of temperature were evaluated taking βvalues into calculation.
Received: 28 August 1996 Accepted: 5 November 1996 相似文献
3.
The effect of cosolvent on micellization of hexadecyltrimethyl ammonium bromide (CTAB) in aqueous solutions was studied. The
conductivity of a mixture (cosolvent + water) as function of CTAB concentration was measured at different temperatures. Ethylene
glycol and ethanol were used as a cosolvent. The conductivity data were used to determine the critical micelle concentration
(CMC) and the effective degree of counterion dissociation of micelle in the temperature range 303.2 to 313.2 K. In all the
cases studied, a linear relationship between log([CMC]mix/mol dm−3) and the mass fraction of cosolvent in solvent mixture has been observed. The free energy (ΔG
mic
0
), enthalpy (ΔH
mic
0
), and entropy (ΔS
mic
0
) of micellization were determined using the temperature dependence of CMC. The dependence of these thermodynamic parameters
on solvent composition was determined. The standard free energy of micellization was found to be negative in all cases and
becomes less negative as the cosolvent content increases. The enthalpy and entropy of micellization are independent of temperature
in pure water, while ΔH
mic
0
and ΔS
mic
0
decrease dramatically with temperature in mixed cosolvents. Furthermore, the entropic contribution is larger than the enthalpic
one in pure water, while in the mixed solvents, the enthalpic contribution predominates.
The text was submitted by the authors in English. 相似文献
4.
Micellar properties of dodecylpyridinium chloride (DPC) were investigated by means of electrical conductometry with emphasis
on the influences of cosolvent-water content and temperature. Ethanol was used as a cosolvent. Conductivity measurements gave
information about critical micelle concentration and micellar ionization degree of the water-ethanol micellar solutions at
different temperatures. In all solvent mixtures, it was observed that the critical micelle concentration of DPC and the degree
of the counterion dissociation increase with an increasing concentration of ethanol and increasing temperature. Micellar and
thermodynamics data were obtained from the temperature dependence of critical micelle concentrations in various aqueous mixtures
of ethanol. In order to explain the effect of the cosolvent, the differences in the Gibbs energies of micellization of DPC
between water and binary cosolvent were determined. The standard free energy (ΔG°mic) of micellization was found to be negative as the concentration of the solvent increases, but it is roughly independent of
temperature. Although the enthalpic contribution was found to be larger than the entropic one, in particular at lower temperatures,
an entropy-enthalpy compensation effect was observed for all systems. Also, enthalpy (ΔH°mic) and entropy (ΔS°mic) of micellization are strongly temperature dependent and decrease with increasing temperature and cosolvent content.
The text was submitted by the authors in English. 相似文献
5.
Surface active micelle formable surfactant-Cr(III) complexes of the type cis-α-[Cr(trien)(C16H33NH2)X]2+ (where trien = triethylenetetramine; X = F−, Cl−, Br−) have been studied in n-alcohol and in formamide at different temperatures by conductance measurements. Standard Gibbs energy changes (ΔG
o
mic), enthalpies (ΔH
o
mic) and entropies (ΔS
o
mic) of micelle formation have been determined by studying the variation of the Critical Micelle Concentration (CMC) with temperature.
Critical micelle concentrations have also been measured as a function of percentage concentration of alcohol added. It is
suggested that alcohol addition leads to an increase in formamide penetration into the micellar interface that depends on
the alcohol chain length. The results are discussed in terms of an increased hydrophobic effect, dielectric constant of the
medium, the chain length of the alcohols and the surfactant in the solvent mixture. 相似文献
6.
The initial reaction rate (V
0) for the esterification reaction of feruloyl esterase (FAE-II) at different temperatures (288, 298, 308, 318, 328, 338, 348,
and 358 K) and various ethyl ferulate concentrations [(2, 4, 6, 8, 10, 12, 14, and 16) × 10−4 mol l−1 of ethyl ferulate in water] were determined. The Lineweaver-Burk double reciprocal plot yielded the kinetic parameters (maximal
velocity V
max, Michaelis constant K
m, and second order rate constant V/K). The effects of temperature on those 3 kinetic parameters were presented and discussed. The thermodynamic parameters ΔH* (enthalpy of activation), ΔG* (free energy of activation), ΔS* (entropy of activation), ΔG
E-S (free energy change of substrate binding), ΔG
E-T (free energy change of transition state formation), related to that biochemical process were determined and discussed from
van’t Hoff plot, Arrhenius plot, and Eyring plot. 相似文献
7.
N. Kumaraguru K. Santhakumar S. Kalyanasundharam 《Journal of solution chemistry》2011,40(10):1673-1686
The critical micelle concentration (CMC) of surfactant–Cr(III)–dodecylamine complexes of the type cis-α-[Cr(trien)(C12H25NH2)X]2+ (where trien = triethylenetetramine; X = F−, Cl−, Br−) has been studied in n-alcohol and in formamide at different temperatures, by electrical conductivity measurements. From the CMC values as a function
of temperature, various thermodynamic properties have been evaluated: standard Gibbs energy changes (Δmic
G
0), standard enthalpy changes (Δmic
H
0) and standard entropy changes (Δmic
S
0) for micellization. Critical micelle concentrations have also been measured as a function of the percentage composition of
alcohol added. The solvent composition dependences of these thermodynamic parameters were determined. It is suggested that
alcohol addition leads to an increase in formamide penetration into the micellar interface that depends on the alcohol’s chain
length. The results are discussed in terms of an increased hydrophobic effect, dielectric constant of the medium, the chain
length of the alcohols, and the surfactant in the solvent mixture. 相似文献
8.
The interfacial tension of aqueous dodecyltrimethylammonium chloride (DTAC) solution/hexane interface has been measured as a function of pressure at concentrations around the critical micelle concentration (CMC). The derivative of the interfacial tension with respect to pressure has been observed to change abruptly at the CMC as in the case of aqueous dodecylammonium chloride (DAC) solution-hexane system studied already. The volume changes associated with the adsorption of DTAC from its monomeric and micellar states have been calculated. The results have indicated that the micelle formation of surfactant is treated like the appearance of a new macroscopic phase in the system. It has also been concluded that the micelle solubilizing hexane bears resemblance to the adsorbed film in terms of the volume. The difference in the pressure dependence of the volume of micelle formation
MW between DTAC and DAC has been attributed to a larger polar group of DTAC. The fact that the value of
MW is larger than that estimated from the conductivity data has been explained by the solubilization of hexane into the micelle. 相似文献
9.
A thermodynamic treatment of the volumetric behavior of surfactant mixtures in water have been developed on the basis of the thermodynamic treatment of mixed micelle by Motomura et al. Densities of aqueous solutions of mixtures of decyltrimethylammonium bromide (DeTAB) and dodecyltrimethylammonium bromide (DTAB) have been measured as a function of total molality at constant compositions. The apparent molar volumes of the mixtures have been derived from the density data and the mean partial molar volume of monomeric surfactant mixture V
t
w
, the molar volume of mixed micelle VM/N
t
M
, the voluem of formation of mixed micelle
W
M
V, and the composition of surfactant in the mixed micelle have been evaluated. The V
t
W
, VM/N
t
M
, and
W
M
V have been observed to depend on the composition. The linear dependence of V
t
W
and VM/N
t
M
on the composition indicates that the mixing of DeTAB and DTAB is ideal both in the monomeric and micellar states. This has been confirmed further by the shape of the critical micelle concentration vs. composition curves. 相似文献
10.
S. P. Chen X. X. Meng Q. Shuai B. J. Jiao S. L. Gao Q. Z. Shi 《Journal of Thermal Analysis and Calorimetry》2006,86(3):767-774
A
solid complex Eu(C5H8NS2)3(C12H8N2) has been obtained from reaction of
hydrous europium chloride with ammonium pyrrolidinedithiocarbamate (APDC)
and 1,10-phenanthroline (o-phen⋅H2O)
in absolute ethanol. IR spectrum of the complex indicated that Eu3+
in the complex coordinated with sulfur atoms from the APDC and nitrogen atoms
from the o-phen. TG-DTG investigation provided
the evidence that the title complex was decomposed into EuS.
The
enthalpy change of the reaction of formation of the complex in ethanol, Δr
H
m
θ(l), as –22.214±0.081 kJ mol–1,
and the molar heat capacity of the complex, c
m,
as 61.676±0.651 J mol–1 K–1,
at 298.15 K were determined by an RD-496 III type microcalorimeter. The enthalpy
change of the reaction of formation of the complex in solid, Δr
H
m
θ(s), was calculated as 54.527±0.314 kJ mol–1
through a thermochemistry cycle. Based on the thermodynamics and kinetics
on the reaction of formation of the complex in ethanol at different temperatures,
fundamental parameters, including the activation enthalpy (ΔH
≠
θ),
the activation entropy (ΔS
≠
θ),
the activation free energy (ΔG
≠
θ),
the apparent reaction rate constant (k),
the apparent activation energy (E), the
pre-exponential constant (A) and the reaction
order (n), were obtained. The constant-volume
combustion energy of the complex, Δc
U,
was determined as –16937.88±9.79 kJ mol–1
by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy
of combustion, Δc
H
m
θ,
and standard enthalpy of formation, Δf
H
m
θ,
were calculated to be –16953.37±9.79 and –1708.23±10.69
kJ mol–1, respectively. 相似文献
11.
R. F. Balabaeva 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(7):1288-1290
Using the experimental values ΔH
Hexc and ΔS
Hexc (ΔH
Nexc and ΔS
Nexc) for solid solutions of hydrogen and nitrogen in molybdenum, we calculate the parameters ɛHMand ɛNM of interaction between hydrogen (nitrogen) and molybdenum lattice doped with small additives of transition metals M; the
values of the activity coefficients on hydrogen and nitrogen γHM and γNM, ΔH
H, ΔH
N, ΔS
H, ΔS
N; enthalpy (ηHM and ηNM) and entropy (σHM and σNM) parameters of interaction over the 1100–1300 K range for alloys of Mo1 − y
M
y
H
x
and Mo1 − y
M
y
N
x
types (y = 0.01 and 0.02; x = 0.01 and 0.02). 相似文献
12.
Muhammad Sultan Hajira Tahir Khalid Ahmed Qazi Jahanzeb 《Frontiers of Chemistry in China》2011,6(2):105-112
The kinetics of the reaction of Fast Green dye (FG) with cetylpyridinum chloride was studied in alkaline medium by UV-Visible
spectrophotometer. Reduction of Fast Green dye was carried out by varying the fast green dye concentration, cetylpyridinum
chloride concentration and concentration of sodium hydroxide. In the present study the reduction of dye was carried out in
order to reduce the color content. The interaction of dye was carried out with reducing analyte (cetylpyridinum chloride).
The rate of the reaction was determined by varying the above parameters at different temperatures. It was observed that the
reduction followed pseudo first-order kinetics with respect to dye, surfactant, OH− ion concentration according to the following reaction pathway. The mechanism for the photo bleaching of the dye has been
proposed and well confirmed by the data simulation procedure. The activation parameters of the reaction like entropy of activation
(ΔS) and free energy of activation (ΔG) showed the extremely solvated states of transient complex which was less disorderly arranged than the oxidized form of dye,
whereas E
a
values reflects a high amount of energy required for the reduction of dye with cetylpyridinum chloride. 相似文献
13.
Summary Results are presented of studies of packings containing copper (II) acetylacetonate (acac), hexafluoroacetylacetonate (hfac),
and chloride, chemically bonded via β-dik-etonate groups. The retention parameters retention factor (k) specific retention volume (V
g), and molecular retention index (M
e) were measured and used to calculate the thermodynamic parameters free energy of adsorption (ΔG
a) heat of adsorption (−ΔH
a), and entropy of adsorption (ΔS
a). These parameters enable, characterization of specific interactions between aromatic and cyclic hydrocarbons, ethers and
thioethers and metal complexes chemically bonded, to a silica surface. 相似文献
14.
Catalytic activity of catalase (CAT) immobilized on a modified silicate matrix to mediate decomposition of meta-chloroperoxibenzoic
acid (3-CPBA) in acetonitrile has been investigated by means of quantitative UV-spectrophotometry. Under the selected experimental
conditions, the kinetic parameters: the apparent Michaelis constat (K
M
), the apparent maximum rate of enzymatic reaction (V
max
app
), the first order specific rate constants (k
sp
), the energy of activation (E
a
) and the pre-exponential factor of the Arrhenius equation (Z0) were calculated. Conclusions regarding the rate-limiting step of the overall catalytic process were drawn from the calculated
values of the Gibbs energy of activation ΔG*, the enthalpy of activation ΔH*, and the entropy of activation ΔS*. 相似文献
15.
The novel ternary solid complex Gd(C5H8NS2)3(C12H8N2) has been obtained from the reaction of hydrous gadolinium chloride, ammonium pyrrolidinedithiocarbamate (APDC), and 1,10-phenanthroline
(o-phen · H2O) in absolute ethanol. The complex was described by an elemental analysis, TG-DTG, and an IR spectrum. The enthalpy change
of the complex formation reaction from a solution of the reagents, Δr
H
m
ϑ
(sol), and the molar heat capacity of the complex, c
m
, were determined as being − 15.174 ± 0.053 kJ/mol and 72.377 ± 0.636 J/(mol K) at 298.15 K by using an RD496-III heat conduction
microcalorimeter. The enthalpy change of a complex formation from the reaction of the reagents in a solid phase, Δr
H
m
ϑ
(s), was calculated as being 52.703 ± 0.304 kJ/mol on the basis of an appropriate thermochemical cycle and other auxiliary
thermodynamic data. The thermodynamics of the formation reaction of the complex was investigated by the reaction in solution.
Fundamental parameters, the activation enthalpy (ΔH
≠
ϑ
), the activation entropy (ΔS
≠
ϑ
), the activation free energy (ΔG
≠
ϑ
), the apparent reaction rate constant (k), the apparent activation energy (E), the preexponential constant (A), and the reaction order (n), were obtained by the combination of the thermochemical data of the reaction and kinetic equations, with the data of thermokinetic
experiments. The constant-volume combustion energy of the complex, Δc
U, was determined as being −17588.79 ± 8.62 kJ/mol by an RBC-II type rotatingbomb calorimeter at 298.15 K. Its standard enthalpy
of combustion, Δc
H
m
ϑ
, and standard enthalpy of formation, Δf
H
m
ϑ
, were calculated to be −17604.28 ± 8.62 and −282.43 ± 9.58 kJ/mol, respectively.
The text was submitted by the authors in English. 相似文献
16.
Mixed micelle formation and surface tension reduction effectiveness (γcmc) were investigated for the following systems: triethanolammonium dodecylpoly(oxyethylene)sulfate (TADPS, containing about
two ethylene oxide units)/dodecyltrimethylammonium bromide, TADPS/hexadecyltrimethylammonium bromide and TADPS/hexadecylpyridinium
chloride. For all these anionic/cationic systems, the mixed critical micelle concentration (cmc) values reflect a strong synergism
in mixed micelle formation, with βM values ranging from −13.8 to −18.3. The mixed micelle composition is mixing-ratio dependent and, for equimolar mixtures,
the mixed micelle is richer in the surfactant with the lower cmc. Precipitation is inhibited to a certain extent, thanks to
the presence of ethylene oxide groups in the anionic species. The conditions for synergism in γcmc, differently expressed in the literature, can be derived from the surface tension equations established in our previous article.
They can be conveniently described by a few characteristic constants: Γ
i
∞ (saturated Gibbs excess), K
i
(constant in the Szyszkowski equation), the cmc of the individual surfactants and the interaction parameters, βS and βM, of their mixtures. Excellent agreement between theoretically predicted and experimental results is obtained. With the increase
in surfactant chain length, the βM values decrease faster than the βS ones and this can result in the loss of synergism in γcmc.
Received: 11 June 2000 Accepted: 4 September 2000 相似文献
17.
Francisco Ros Pilar Jiménez María Victoria Roux 《Monatshefte für Chemie / Chemical Monthly》2007,138(10):941-949
Summary. The cohesion potential energy of the crystal of one enantiomer of ethyl 3-cyano-3-(3,4-dimethyloxyphenyl)-2,2,4-trimethylpentanoate,
−47.7 ± 0.1 kJ mol−1 (0–90°C), was found out from the heat of sublimation (123.2 ± 5.1 kJ mol−1, 78.6°C) and the kinetic energies for the gas phase and the crystal. It was found that the entropy function of Debye’s theory of solids mathematically agreed with the vibrational entropy of the gas (variationally obtained), allowing to disclose
the vibrational energy using the Debye energy function (E
vib 835.0 kJ mol−1 (78.6°C), E
0 included). E
kin for the crystal (771.1 kJ mol−1 (78.6°C)) was obtained by Debye’s theory with the experimental heat capacity. The cohesion energy represented a moderate part of the sublimation energy.
The cohesion energy of the racemic crystal, −44.2 kJ mol−1, was obtained by the heat of formation of the crystal in the solid state (3.0 kJ mol−1, 83.3°C) and E
kin for the crystal (by Debye’s theory). The decrease in cohesion on formation of the crystal accounted for the energy of formation. The change in potential
energy on liquefaction of the racemate from the gas state was disclosed obtaining added-up E
vib + rot for the liquid in the way as to E
vib for the gas, the Debye entropy function being increasedly suited for the liquid (E
vib + rot 763.4 kJ mol−1 (115.4°C)). Positive ΔE
pot, 13.0 kJ mol−1, arised from the increase in electronic energy (Δ
l
νmean − 154.3 cm−1, by the dielectric nature of the liquid), added to the cohesion energy. 相似文献
18.
Hong-Lin Zhang Zhe Kong Yong-Mei Yan Gan-Zuo Li Li Yu Fei Geng 《Journal of solution chemistry》2008,37(12):1631-1644
The power-time curves for the micelle formation process were determined for two anionic surfactants, sodium laurate (SLA)
and sodium dodecyl sulfate (SDS), in mixed alcohol + N,N-dimethylacetamide (DMA) solvent using titration microcalorimetry.
From the data of the lowest point and the area of the power-time curves, their critical micelle concentration (CMC) and ΔH
mo were obtained. The other thermodynamic functions of the micellization process (ΔG
mo and ΔS
mo) were also calculated with thermodynamic equations. For both surfactants, the effects of the carbon number (chain length)
of the alcohol, the concentration of alcohol, and the temperature on the CMC and thermodynamic functions are discussed. For
systems containing identical concentrations of a different alcohol, values of the CMC, ΔH
mo and ΔS
mo increased whereas ΔG
mo decreased with increasing temperature. For systems containing an identical alcohol concentration at the same temperature,
values of the CMC, ΔH
mo,ΔG
mo and ΔS
mo decrease with increasing carbon number of alcohol. For systems containing the same alcohol at the same temperature, the CMC
and ΔG
mo values increase whereas ΔH
mo and ΔS
mo decrease with increasing alcohol concentration. 相似文献
19.
Francisco Ros Pilar Jiménez María Victoria Roux 《Monatshefte für Chemie / Chemical Monthly》2007,28(4):941-949
The cohesion potential energy of the crystal of one enantiomer of ethyl 3-cyano-3-(3,4-dimethyloxyphenyl)-2,2,4-trimethylpentanoate,
−47.7 ± 0.1 kJ mol−1 (0–90°C), was found out from the heat of sublimation (123.2 ± 5.1 kJ mol−1, 78.6°C) and the kinetic energies for the gas phase and the crystal. It was found that the entropy function of Debye’s theory of solids mathematically agreed with the vibrational entropy of the gas (variationally obtained), allowing to disclose
the vibrational energy using the Debye energy function (E
vib 835.0 kJ mol−1 (78.6°C), E
0 included). E
kin for the crystal (771.1 kJ mol−1 (78.6°C)) was obtained by Debye’s theory with the experimental heat capacity. The cohesion energy represented a moderate part of the sublimation energy.
The cohesion energy of the racemic crystal, −44.2 kJ mol−1, was obtained by the heat of formation of the crystal in the solid state (3.0 kJ mol−1, 83.3°C) and E
kin for the crystal (by Debye’s theory). The decrease in cohesion on formation of the crystal accounted for the energy of formation. The change in potential
energy on liquefaction of the racemate from the gas state was disclosed obtaining added-up E
vib + rot for the liquid in the way as to E
vib for the gas, the Debye entropy function being increasedly suited for the liquid (E
vib + rot 763.4 kJ mol−1 (115.4°C)). Positive ΔE
pot, 13.0 kJ mol−1, arised from the increase in electronic energy (Δ
l
νmean − 154.3 cm−1, by the dielectric nature of the liquid), added to the cohesion energy. 相似文献
20.
Photon transmission technique was used to monitor the evolution of transparency during film formation from poly(vinyl acetate) (PVAc) latex particles. The latex films were prepared below the glass transition temperature (T
g) of PVAc. These films were annealed at elevated temperatures in various time intervals above the T
g of PVAc. It is observed that transmitted photon intensity (I
tr) from these films increased as the annealing temperature is increased. It is seen from I
tr curves that there are two film formation stages. These successive stages are named void closure (viscous flow) and interdiffusion. The activation energies for viscous flow (ΔH) and backbone motion (ΔE
b) were obtained by using well-defined models. The averaged values of the backbone (ΔE
b) and the viscous flow activation energies (ΔH) were found to be 188.6 and 5.6 kcal/mol, respectively. The minimum film formation (τ
M,T
M) and healing points (τ
H,T
H) were determined. Minimum film formation (ΔE
M) and healing activation energies (ΔE
H) were measured using these time–temperature pairs. ΔE
M and ΔE
H were found to be 32.5 and 28.3 kcal/mol, respectively. 相似文献