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1.
Yan Bai Gui-Ying Xu Xia Xin Hong-Yuan Sun Hong-Xing Zhang Ai-You Hao Xiao-Deng Yang Lin Yao 《Colloid and polymer science》2008,286(13):1475-1484
The interaction between cetyltrimethylammonium bromide (CTAB) and β-cyclodextrin (β-CD) was studied via surface tension and
dilational viscoelasticity methods. The effect of sodium bromide and sodium chloride on the interaction between CTAB and β-CD
were studied as well. The surface tension isotherms provided a series of parameters, including apparent critical micelle concentration
(cmc*), surface tension at the cmc* (γcmc), stoichiometry of the complex (R), and the efficiency of adsorption (pC
20
). The addition of NaBr and NaCl decreases the cmc* of CTAB/β-CD solution. CTAB molecules enter the cavities of β-CD molecules
thus formed both 1:1 and 1:2 inclusion complexes. From the change of γcmc, it can be seen that the CTAB/β-CD complexes (1:1) act as short-chain alcohol, which decrease γcmc, but the depression of cmc* is too small to be detected. R first decreases then increases as a function of NaBr and NaCl. Compared to NaCl, NaBr increases R more efficiently. The presence of NaBr and NaCl increases pC
20
of CTAB/β-CD solution. The results obtained from the dilational viscoelasticity measurements at low dilational frequencies
(0.005–0.1 Hz) reveal that the dilational modulus passes through a maxium value with increasing concentration of β-CD at a
given concentration of CTAB. The addition of both NaBr and NaCl decreases the dilational modulus of a given concentration
CTAB/β-CD solution.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 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.
Lei Zhang Xin Lv Yuejun Zhu Jian Zhang Hong Wang Yebang Tan 《Colloid and polymer science》2011,289(14):1579-1587
The polymeric surfactant with quaternary ammonium salt (PQ) was synthesized by cationic ring-open polymerization using boron
trifluoride diethyletherate as cationic catalyst. The chemical structure and aggregation behavior of PQ were studied by 1H NMR, surface tension, static light scattering, dynamic laser light scattering, electrical conductivity, and fluorescence
measurement. The results show the surface tension (γcmc) and critical micelle concentration (cmc) of PQ decrease with increasing of sodium chloride concentration. The cmc and γcmc values of PQ measured by electrical conductivity and fluorescence measurements mainly identify with that obtained by surface
tension measurements. The thermodynamic parameters (DGm0 \Delta G_m^0 ,DHm0 \Delta H_m^0 ,DSm0 \Delta S_m^0 ) from electrical conductivity indicated that the micellization of PQ was mainly the process of entropy-driven. In addition,
the results from the viscosity stability between hydrolyzed polyacrylamide (HPAM) and PQ showed that the viscosities of mixed
system for HPAM and PQ are higher than the viscosity of HPAM. 相似文献
4.
Sodium (3-dodecanoyloxy-2-hydroxy-propyl) succinate (SLGMS) is a conjugated anionic surfactant in which a glycerol residue
connects with a hydrophilic sodium succinate and dodecanoate. Aqueous micellar phase (Wm), hexagonal (H1), bicontinuous cubic (V1), and lamellar (Lα) phases are successively formed with increasing the surfactant concentration in a binary SLGMS-water system. The Krafft point
is below 0 °C. The effective cross sectional area per surfactant molecule, a
s, in the H1 phase is almost constant, 0.5 nm2, and the shape of cylindrical micelle is almost unchanged with surfactant concentration. The cmc value of SLGMS measured
by means of surface tension, electrical conductivity, and fluorescence probe methods is in the range of 4∼9 × 10−5 mol/l that is much lower than that of sodium dodecanoate, 2 × 10−2 mol/l, or SDS, 8 × 10−3 mol/l. Hence, it is considered that the polar glycerol part in the SLGMS acts as a hydrophobic part. The solubilization of
oil in the SLGMS solution is much higher than that in the SDS solution and this also suggests that the glycerol and succinic
units act as lipophilic moieties.
Received: 15 June 2000/Accepted: 27 July 2000 相似文献
5.
D. Y. Kwok A. Leung A. Li C. N. C. Lam R. Wu A. W. Neumann 《Colloid and polymer science》1998,276(6):459-469
Low-rate dynamic contact angles of 22 liquids on a poly(n-butyl methacrylate) (PnBMA) polymer are measured by an automated axisymmetric drop shape analysis-profile (ADSA-P). It is found that 16 liquids yielded
non-constant contact angles, and/or dissolved the polymer on contact. From the experimental contact angles of the remaining
6 liquids, it is found that the liquid–vapor surface tension times cosine of the contact angle changes smoothly with the liquid–vapor
surface tension, i.e. γlv cos θ depends only on γlv for a given solid surface (or solid surface tension). This contact angle pattern is in harmony with those from other inert
and non-inert (polar and non-polar) surfaces [34–37, 45–47]. The solid–vapor surface tension calculated from the equation-of-state
approach for solid-liquid interfacial tensions [14] is found to be 28.8 mJ/m2, with a 95% confidence limit of ±0.5 mJ/m2, from the experimental contact angles of the 6 liquids.
Received: 12 September 1997 Accepted: 22 January 1998 相似文献
6.
Sancheeta Kolay Kallol K. Ghosh Amy MacDonald Jonathan Moulins Rama M. Palepu 《Journal of solution chemistry》2008,37(1):59-72
The thermodynamics of micellization and other micellar properties of alkyl- (C10-, C12-, C14- and C16-) triphenylphosphonium bromides in water + ethylene glycol (EG) (0 to 30% v/v) mixtures over a temperature range of 298 to
318 K and cetyltriphenylphosphonium bromide in water + diethylene glycol (DEG) mixtures (0 to 30% v/v) at 298 K have been
studied conductometrically. In all cases, an increase in the percentage of co-solvent results in an increase in the cmc values.
On the basis of these results, the thermodynamic parameters, the Gibbs energy (ΔG
mo), enthalpy (ΔH
mo) and entropy (ΔS
mo) of micellization have been evaluated. In addition to the conductivity measurements, kinetic experiments have also been done
to determine the dependence of observed rate constant for the nucleophilic substitution reaction of p-nitrophenyl acetate and benzohydroxamate ions in the presence of the surfactant cetyltriphenylphosphonium bromide with a
varying concentration of EG and DEG ranging from 0 to 50% v/v at pH=7.9 and 300 K. All of the reactions followed pseudo-first-order
kinetics. An increase in the surfactant concentration results in an increase in the reaction rate and for a given surfactant
concentration, the rate constant decreases as the concentration of co-solvent in the mixture increases. The kinetic micellar
effects have been explained by using the pseudophase model. The thermodynamic and structural changes originating from the
presence of solvents control the micellar kinetic effects. 相似文献
7.
J. N. Zhang Z. C. Tan Q. F. Meng Q. Shi B. Tong S. X. Wang 《Journal of Thermal Analysis and Calorimetry》2009,95(2):461-467
The heat capacities (C
p,m) of 2-amino-5-methylpyridine (AMP) were measured by a precision automated adiabatic calorimeter over the temperature range
from 80 to 398 K. A solid-liquid phase transition was found in the range from 336 to 351 K with the peak heat capacity at
350.426 K. The melting temperature (T
m), the molar enthalpy (Δfus
H
m0), and the molar entropy (Δfus
S
m0) of fusion were determined to be 350.431±0.018 K, 18.108 kJ mol−1 and 51.676 J K−1 mol−1, respectively. The mole fraction purity of the sample used was determined to be 0.99734 through the Van’t Hoff equation.
The thermodynamic functions (H
T-H
298.15 and S
T-S
298.15) were calculated. The molar energy of combustion and the standard molar enthalpy of combustion were determined, ΔU
c(C6H8N2,cr)= −3500.15±1.51 kJ mol−1 and Δc
H
m0 (C6H8N2,cr)= −3502.64±1.51 kJ mol−1, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. The standard molar enthalpy of formation of the crystalline compound was derived, Δr
H
m0 (C6H8N2,cr)= −1.74±0.57 kJ mol−1. 相似文献
8.
W Zielenkiewicz R Swierzewski F Attanasio G Rialdi 《Journal of Thermal Analysis and Calorimetry》2006,83(3):587-595
Investigations
of lysozyme–polyethylene glycol system were made by differential scanning
calorimetry, fluorescence and density techniques. The values of unfolding
enthalpies, ΔHNU, unfolding temperatures, Tm,
excess molar heat capacities, ΔCp,
and apparent molar volumes, VΦ
, were determined as functions of PEG concentration. The three PEGs of average
molecular mass (MW) 6000, 10000, 20000
were used as macromolecular crowding agents. The concentration of polymers
was changed in the range 0–30% mass per volume (w/v). The values of ΔHNU remained
constant with no dependence on PEG concentration, while PEG addition to buffered
lysozyme solutions caused linear decrease of Tm.
The values of ΔCp
and VΦ of lysozyme
dramatically changed in the range of 8–10% of PEG concentration. The
fluorescence spectroscopy was used in order to investigate the polymer influence
on possible solvent–lysozyme interactions. The electrical properties
of polymer–water and polymer–buffer systems, the dielectric constants
of solutions were determined with use of impedance spectroscopy. 相似文献
9.
Narayanasamy Kumaraguru Sankarlingam Arunachalam Mahadevimanglam Narayanasamy Arumugham Kannappan Santhakumar 《Transition Metal Chemistry》2006,31(2):250-255
A number of mixed ligand chromium(III)–surfactant coordination complexes, of the type cis-[Cr(en)2(A)X]2+ and cis-α-[Cr(trien)(A)X]2+ (A = Dodecyl or Cetylamine; X = F−, Cl−, Br−) were synthesized from the corresponding dihalogeno complexes by ligand substitution. These compounds form foam in aqueous
solution when shaken. The critical micelle concentration (CMC) values of these surfactant metal complexes in aqueous solution
were obtained from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for evaluation of the
temperature-dependent critical micelle concentration (cmc) and the thermodynamics of micellization (Δ Gm0, Δ Hm0 and Δ Sm0). 相似文献
10.
N. Hattori H. Hirata H. Okabayashi M. Furusaka C. J. O'Connor R. Zana 《Colloid and polymer science》1999,277(1):95-100
The microstructure of the normal micelles formed by dimeric surfactants with long spacers, [Br−(CH3)2N+(C
m
H2
m
+1)-(CH2)
S
-(C
m
H2
m
+1)N+(CH3)2Br−, m = 10 and s = 8, 10 and 12], has been investigated by small-angle neutron scattering and compared with previously reported results for
micelles of the same dimeric surfactants with shorter spacers (m = 10 and s = 2, 3, 4 and 6). It was found that for dimeric surfactants with long spacers (s = 8 and 10), both micellar growth and variation in shape occur to only a small extent, if at all, compared with dimeric surfactants
with short spacers. However, for the dimeric surfactant with the longest spacer, s = 12, the extent of micellar growth and shape variation is also large. These results are due to the differences in conformation
of dimeric surfactants with short spacers (s = 2–6) compared with that of the surfactants with long spacers (s = 8–12).
Received: 15 June 1998 Accepted: 22 July 1998 相似文献
11.
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
12.
Raman scattering spectra and molecular conformations of bis(quaternaryammonium bromide)-water systems 总被引:1,自引:0,他引:1
The dimeric bis(quaternaryammonium bromide) surfactants, [Br−(CH3)2N+(C
m
H2
m
+1)—(CH2)
s
—(C
m
H2
m
+1)N+(CH3)2Br−, s = 2, 3 and m = 4, 6, 10 and 12, s = 6 and m = 8, 10, 12], have been synthesized and the phase maps of the sm6-8-water, sm6-10-water and sm6-12-water binary systems have
been determined (sm6-8 implies s = 6, m = 8). In order to examine the molecular structures of these solid samples and of their dimeric surfactant-water binary systems,
Raman spectra of the simple dimeric surfactants, sm2-4 and sm3-4, in which crystal structures of the trans- and cis-type conformations
have been determined by single-crystal X-ray diffraction analysis, have been investigated, and Raman bands characteristic
of these skeletal structures were found in the skeletal deformation region. On the basis of these characteristic Raman bands
for the two conformations, it has been concluded that the dimeric surfactants, sm6-8, sm6-10 and sm6-12 also take up a cis-type
conformation in the crystalline state. Furthermore, it has been found that the Raman bands in the C—H stretching, skeletal
stretching and CH2 scissoring regions are sensitive to phase structure.
Received: 21 July 1998 Accepted in revised form: 9 November 1998 相似文献
13.
The standard molar enthalpy of formation Δf
H
m
0=–760±12 kJ for amorphous silicon nitride a-Si3N4 has been determined from fluorine combustion calorimetry measurements of the massic energy of the reaction: a-Si3N4(s)+6F2(g)=3SiF4(g)+2N2(g). This value combined with Δf
H
m
0= –828.9±3.4 kJ for a-Si3N4 indicates that determined for the first time molar enthalpy change for the transition from amorphous to α-crystalline form
Δtrs
H
m
0=69±13 kJ is very evident, in spite of its large uncertainty range resulting from impurity corrections.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Mahmoud M. Al Omari Mohammad B. Zughul J. Eric D. Davies Adnan A. Badwan 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(3-4):247-254
The interaction of celecoxib (Celox) with cyclodextrins (CDs) has been investigated by phase solubility techniques. In this study, the influences of CD type, pH, buffer type, buffer concentration and temperature on the tendency of Celox to form inclusion complexes with CDs were examined. The tendency of Celox to complex with CDs is in the order HP-β-CD > β-CD > γ-CD > α-CD, where the complex formation constants (K
11) were 1377, 693, 126 and 60 M−1, respectively. Also ionization of the slightly acidic Celox (pK
a=9.7) was found to reduce its tendency to complex (i.e., The K
11 values of Celox/β-CD in 0.05 M phosphate buffer were 976 and 210 M−1 for neutral and ionized Celox, respectively). Increasing citrate and phosphate buffer concentration enhances the tendency of ionized Celox to complex with β-CD as a result of a corresponding decrease in the inherent solubility (S
0) of the Celox anion. On the other hand, these two buffers interact differently with neutral Celox and β-CD, where increasing phosphate buffer concentration at low pH enhances the complexation of neutral Celox by lowering S
0, while increasing citrate buffer concentration at low pH reduces complex formation as citrate buffer species, mainly citric acid, act as a solublizer and a competitor for Celox and β-CD. The contribution of Celox hydrophobicity for complex stability constitutes about 77% of the driving force for complex stability. The complex formation of neutral Celox with β-CD (ΔG
0=−28.6 kJ/mol) is driven by both enthalpy (ΔH
0=−21.7 kJ/mol) and entropy (ΔS
0=23.3 J/mol K) changes. 相似文献
15.
W. Zielenkiewicz I. V. Terekhova M. Koźbiał R. S. Kumeev 《Journal of Thermal Analysis and Calorimetry》2010,101(2):595-600
The inclusion complex formation of riboflavin (RF) with hydroxypropyl-β-cyclodextrin (HP-β-CD) in water was investigated by
1H NMR, UV-vis spectroscopy, and solubility methods. A 1:1 stoichiometry and thermodynamic parameters of complex formation
(K, Δc
G
0, Δc
H
0, and Δc
S
0) were determined. Complexation was characterized by negative enthalpy and entropy changes due to prevalence of van der Waals
interactions and hydrogen bonding between polar groups of the solutes. A partial insertion of RF into macrocyclic cavity was
revealed on the basis of 1H NMR data and molecular mechanics calculation. Location of benzene ring of RF molecule inside the hydrophobic cavity of HP-β-CD
results in an increase of aqueous solubility of the former. 相似文献
16.
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
17.
M. A. V. Ribeiro da Silva C. P. F. Santos M. J. S. Monte C. A. D. Sousa 《Journal of Thermal Analysis and Calorimetry》2006,83(3):533-539
The
standard (p0=0.1
MPa) molar enthalpies of formation, ΔfHm0, for
crystalline phthalimides: phthalimide, N-ethylphthalimide
and N-propylphthalimide were derived from
the standard molar enthalpies of combustion, in oxygen, at the temperature
298.15 K, measured by static bomb-combustion calorimetry, as, respectively,
– (318.0±1.7), – (350.1±2.7) and – (377.3±2.2)
kJ mol–1. The standard molar enthalpies of
sublimation, ΔcrgHm0, at T=298.15
K were derived by the Clausius-Clapeyron equation, from the temperature dependence
of the vapour pressures for phthalimide, as (106.9±1.2) kJ mol–1
and from high temperature Calvet microcalorimetry for phthalimide, N-ethylphthalimide and N-propylphthalimide
as, respectively, (106.3±1.3), (91.0±1.2) and (98.2±1.4)
kJ mol–1.
The derived standard molar enthalpies of formation,
in the gaseous state, are analysed in terms of enthalpic increments and interpreted
in terms of molecular structure. 相似文献
18.
Mingqi Ao Peipei Huang Guiying Xu Xiaodeng Yang Yajing Wang 《Colloid and polymer science》2009,287(4):395-402
The aggregation behavior and thermodynamic properties of micellization for the ionic liquid-type gemini imidazolium surfactants
with different spacer length ([C12–s–C12im]Br2, s = 2, 4, 6) have been investigated by means of surface tension, electrical conductivity, dynamic light scattering and fluorescence
measurements. The values of cmc, γ
cmc, Γ
max, A
min, π
cmc, pc20 and cmc/pc20 suggest that the shorter the spacer, the higher the surface activity of [C12–s–C12im]Br2 is. The cmc and γ
cmc values are decreased significantly in the presence of sodium halides, and the values decrease in the order NaCl < NaBr < NaI.
The thermodynamic parameters of micellization (, , ) indicate that the micellization of [C12–2–C12im]Br2 and [C12–4–C12im]Br2 is entropy-driven, whereas aggregation of [C12–6–C12im]Br2 is enthalpy-driven at lower temperature but entropy-driven at higher temperature. Finally, the fluorescence measurements
show that the micropolarity of micelles increases but the aggregation numbers decrease with increasing the spacer length of
[C12–s–C12im]Br2. 相似文献
19.
The complex formation of native and substituted β-cyclodextrins with m-aminobenzoic acid in water was characterized by calorimetry, 1H NMR and UV spectroscopic studies. These studies showed that β-, hydroxypropyl-β- and methyl-β-cyclodextrins form 1:1 inclusion complexes with m-aminobenzoic acid. The thermodynamic properties of complex formation (K,Δc
G
o,Δc
H
o,Δc
S
o) were calculated. It was found that the processes of complexation are mainly favorable entropically. Introduction of hydroxypropyl-
and methyl-substituents into the β-CD molecule results in negligible enhancement of stability of the complexes formed. The structure of these substituents has
no influence on the stability constant values. The insertion of the carboxylic group of m-aminobenzoic acid into the cyclodextrin cavity was confirmed by 1H NMR data. 相似文献
20.
Wolfgang Preis Michael Holzinger Werner Sitte 《Monatshefte für Chemie / Chemical Monthly》2001,132(4):499-508
Summary. The van der Pauw method has been applied to conductivity relaxation experiments on YBa2Cu3O6+δ at 600°C in order to determine the chemical diffusion coefficient as a function of the oxygen partial pressure in the surrounding
atmosphere (100 > p
O
2/bar > 10−3). It is shown that the van der Pauw technique is suitable for monitoring the conductivity relaxation when the oxygen diffusion is perpendicular to the direct
current flowing through the sample in accordance with the van der Pauw geometry using thin tablets as samples. The oxygen partial pressure is changed stepwise (generally Δlogp
O
2 ≤ 0.5) by employing appropriate gas mixtures as well as an electrochemical oxygen pump device. An evaluation formula is given
for the determination of the chemical diffusion coefficient neglecting slow surface processes. In addition, the electronic
conductivity of YBa2Cu3O6+δ has been measured at 600°C as a function of oxygen partial pressure of the ambient atmosphere (100 > p
O
2/bar > 10−5) by means of the van der Pauw method applying the same experimental set-up. Typical values of the chemical diffusion coefficient are in the range of 10−6 cm2·s−1; the results of the conductivity measurements are interpreted in terms of an appropriate defect model.
Received May 30, 2000. Accepted June 8, 2000 相似文献