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1.
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
2.
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
3.
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
4.
Micellization of monomeric and dimeric (gemini) surfactants in polar nonaqueous-water-mixed solvents
Kabir-ud-Din Umme Salma Siddiqui Sanjeev Kumar Aijaz Ahmad Dar 《Colloid and polymer science》2006,284(7):807-812
Dimeric or gemini surfactants are novel surfactants that are finding a great deal of discussion in the academic and industrial arena. They consist of two hydrophobic chains and two polar head groups covalently linked by a spacer. Data on critical micelle concentration (cmc) and degree of counterion dissociation (α) are reported on bis-cationic C16H33N+(CH3)2–(CH2)s–N+(CH3)2C16H33, 2Br−, referred to as 16-s-16, for spacer lengths s=4, 5, 6 in aqueous and in polar nonaqueous (1-propanol, 2-methoxyethanol or methyl cellosolve, dimethyl sulfoxide, acetonitrile)-water-mixed solvents. The behavior is compared with conventional monomeric surfactant cetyltrimethylammonium bromide (CTAB). Thermodynamic parameters are obtained from the temperature dependence of the cmc values. It is observed that micellization tendency of the surfactants decreases in the presence of polar nonaqueous solvents. However, detailed studies with dimethylsulfoxide (DMSO) show that the geminis nearly outclass the micellization-arresting property of this solvent. Also, within geminis, higher spacer length is found suitable for showing micellization even with high DMSO content (50% v/v). The implications of these results of gemini micellization may be useful in micellar catalysis in polar nonaqueous solvents. 相似文献
5.
S. P. Gabuda S. G. Kozlova D. N. Dybtsev V. P. Fedin 《Journal of Structural Chemistry》2009,50(5):887-894
By the 1H NMR and Raman spectroscopy data it is shown that in the porous inclusion compound of Zn2(C8H4O4)2[(N2(CH2)6))]·n(CH3)2CO (n ≈ 0–4.7) acetone molecules exist in two structural forms: ketonic (CH3)2CO, for which the 1H NMR chemical shift value is δket = 0.8 ppm, and enolic CH3C(O)=CH2, for which δen(OH) = 11 ppm, δen(CH2) = 8.9 ppm, and δen(CH3) = 1.6 ppm are found, the average value over three proton sites being <δen> = 5.6 ppm. A sharp difference in chemical shift values for the keto and enol forms of acetone in the inclusion compounds
can be assigned to the effect of structural chemical conditions in two types of adsorption centers. 相似文献
6.
Harrison AG 《Journal of the American Society for Mass Spectrometry》2012,23(1):116-123
The doubly-protonated peptides Ala-Ala-Xaa-Ala-Ala-Ala-Arg show extensive loss of H2O when Xaa = Ser or Thr. Using quasi-MS3 techniques the fragmentation reactions of the [M + 2H – H2O]+2 ions have been studied in detail. For both Ser and Thr, the [M + 2H – H2O]+2 ions show three primary fragmentation reactions, elimination of CH3CH = NH, elimination of one Ala residue, and elimination of two Ala residues, in all cases forming doubly-charged products.
From a study of the further fragmentation of these products, it is concluded that elimination of two Ala residues results
in formation of a three-membered aziridine ring by interaction with the adjacent amide function as H2O is lost. The elimination of one Ala residue results in formation of a five-membered oxazoline ring through interaction with
the N-terminal adjacent carbonyl function as H2O is lost. The elimination of CH3CH = NH appears to involve formation of an eight-membered ring by interaction with the remote N-terminal carbonyl function
as H2O is lost. However, this initial structure undergoes rearrangement through interaction with the adjacent C-terminal carbonyl
function prior to further fragmentation. The [MH – H2O]+ ion of Ala-Ala-Ser-Ala-Ala-Ala also shows elimination of CH3CH = NH, one Ala residue and two Ala residues. 相似文献
7.
The microstructure of the micelles formed in aqueous solution by gemini surfactants with aromatic spacers, [Br(CH3)2N+(C
m
H2
m
+1)-(Ph)-(C
m
H2
m
+1)N+(CH3)2Br, m=8 and Ph = o-, m- or p-phenylenedimethylene] has been examined by small-angle neutron scattering. Aggregation of the gemini surfactants with an
o-phenylenedimethylene spacer brings about formation of premicelles and small micelles at concentrations below the second critical
micelle concentration, while above this concentration marked micellar growth and variation in shape occurs. It is suggested
that the minimum aggregate formed at this critical micelle concentration may be the trimer or tetramer and that this result
supports the mechanism of “gemini → submicelle → assembly” for micellar growth.
Received: 8 September 1998 Accepted in revised form: 27 November 1998 相似文献
8.
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
9.
The association behaviour of triblock copoly(ethylene oxide/tetrahydrofuran/ethylene oxide), in particular E100T27E100, in aqueous solutions has been investigated by means of static and dynamic light scattering, nuclear magnetic reso-nance
(NMR) and surface tension techniques. On raising the polymer concentration at room temperature, the copolymer aggregates to
form micelles with an aggregation number of about 105 (R
G, mic≈15 nm and R
H, mic≈13 nm, as revealed by light scattering and FT-PGSE NMR measurements, respectively). The micelles are kinetically quite stable,
the micellar lifetime is shown to be more than 1 h. The residence time of a single unimer in a micelle is more than 140 ms.
The apparent radius of gyration R
G, mic is fairly independent of concentration, but large effects are observed on varying the temperature. Raising the temperature
initially results in an increase of the apparent micellar size, followed by a maximum at an intermediate temperature (≈45 °C).
At higher temperatures a contraction of the micelles is observed. The shape of the micelles also appear to vary in this temperature
interval. The interactions responsible for these phenomena are discussed in terms of, e.g., the temperature-dependent solubility
of the alkylene oxide segments in water and polydispersity effects.
Received: 29 January 1996 acccepted : 4 November 1996 相似文献
10.
I. A. Opeida M. A. Kompanets O. V. Kushch A. G. Matvienko 《Theoretical and Experimental Chemistry》2010,46(2):107-111
The kinetics of the decomposition of the phthalimid-N-oxyl radical (PINO) in acetic acid has been studied. The rate constants
of the addition of the radical to T bonds of molecules of vinyl compounds – styrene, methyl methacrylate, acrylonitrile, and
methyl acrylate – have been measured. It was shown that electron-donor substituents in the monomer molecule increase, while
electron-acceptor substituents decrease the rate of addition. The reactivity of monomers in the elementary step of addition
of the PINO radical decreases in the order CH2=C(CH3)C6H5 > CH2=CHC6H5 > CH2=C(CH3)COOCH3 > CH2=CHCOOCH3 > CH2=CHCN. 相似文献
11.
Silvia Gross Andrea Zattin Vito Di Noto Sandra Lavina 《Monatshefte für Chemie / Chemical Monthly》2006,137(5):583-593
Summary. Silica-based inorganic–organic hybrid thin films embedding the organically modified oxohafnium clusters (Hf4O2(OMc)12, OMc=OC(O)–C(CH3)=CH2) were obtained by photo-activated free radical copolymerisation of the methacrylate groups of the cluster with those of the
pre-hydrolysed (methacryloxypropyl)trimethoxysilane (MAPTMS, (CH2=C(CH3)C(O)O)(CH2)3Si(OCH3)3). By this route, a covalent anchoring of the cluster to the forming silica network was achieved. Samples characterized by
two different Si/Hf compositions (18:1, 5:1) were prepared. The surface and in-depth composition of the thin films were investigated
through Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). XPS depth profiles performed on the thin
layers evidenced a homogenous in depth distribution of the hafnium guest species within the whole silica films and sharp film-substrate
interfaces.
Broad band dielectric spectroscopy (BDS) measurements permitted to investigate the electric response of the obtained films
in the frequency and temperature range of 40 Hz – 1 MHz and 0–160°C. 相似文献
12.
Quantum-mechanical calculations at the self-consistent-field–M?ller–Plesset level have been performed for various compounds
obtained by substituting two or four CH2 groups of the tetrahydrofuran molecule with SiH2 groups, as well as the oxygen with a sulphur atom. Cyclic tetrasilane oxide, (SiH2)4O, and sulphide, (SiH2)4S, are suggested as possible alternatives to the carbon ring of natural sugars for the design of exobiological molecules because
of certain similarities with tetrahydrofuran, (CH2)4O, especially the relatively small energy differences between different conformers and the subsequent ability to cross the
energy barriers between them by puckering on the pseudorotation wheel.
Received: 16 September 1999 / Accepted: 3 February 2000 / Published online: 21 June 2000 相似文献
13.
I. S. Ryzhkina A. P. Timosheva A. V. Chernova R. R. Shagidullin A. A. Gazizova W. D. Habicher T. Krause L. I. Vagapova A. I. Konovalova 《Russian Chemical Bulletin》2007,56(3):475-483
Aggregation of amphiphilic calix[4]resorcinarenes (CRA) modified by carboxymethyl (1), 2-hydroxyethyl (2), methylamino acetal (3), and aminomethyl (4) fragments and their interaction with some synthetic (5, 6) and natural (7, 8) surfactants in the low-polarity solvent (chloroform) were studied by permittivity measurements and FT-IR spectroscopy. Compounds
1–4 and surfactants form aggregates at critical micelle concentrations (CMC) of 2.0·10−5–7.5·10−5 and 1.7·10−5–2.0·10−3 mol L−1, respectively. The CMC values of CRA—surfactant mixed aggregates depend on the surfactant structure and the structure and
concentration of CRA. Analysis of the IR spectra of solutions of a series of amphiphilic CRA (2–4, 9, 10) and their mixtures with the cationic surfactant N-cetyl-N,N-dimethyl-N-(2-hydroxyethyl)ammonium bromide (5) showed that an increase in the concentration of the solutions in individual and mixed systems is accompanied by a decrease
in the molar integral intensities and intensities in the maxima of the absorption bands of the O—H and C—H bonds down to the
CMC point, after which these values change slightly. The discovered effect, which is differently pronounced for all systems
studied, indicates that both the polar “head” groups and nonpolar fragments of CRA and surfactant are involved in the formation
of supramolecules of the reverse micelle type in all cases.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 459–466, March, 2007. 相似文献
14.
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
15.
The reaction of N-benzoylphosphoramidic dichloride with amines afforded some new N-benzoylphos-phoric triamides with formula C6H5C(O)NHP(O)(X)2, X=NH–CH(CH3)2 (1), NH–CH2–CH(CH3)2 (2), NH–CH2–CH(OCH3)2 (3), N(CH3)[CH2CH(OCH3)2] (4) and N(CH3)(C6H11) (5) that were characterized by 1H,13C,31P NMR, IR spectroscopy and elemental analysis. The structures have been determined for compounds 4 and 5 by X-ray crystallography. These compounds contain one amidic hydrogen atom and form centrosymmetric dimmers via intermolecular
–P–O⋯H–N–hydrogen bonds besides weak C–H⋯O hydrogen bonds that lead to three-dimensional polymeric clusters in the crystalline
lattice. 相似文献
16.
Self-consistent reaction field calculation of solvent reorganization energy in electron transfer: a dipole-reaction field interaction model 总被引:1,自引:0,他引:1
Based on the continuum dielectric model, this work has established the relationship between the solvent reorganization energy
of electron transfer (ET) and the equilibrium solvation free energy. The dipole-reaction field interaction model has been
proposed to describe the electrostatic solute-solvent interaction. The self-consistent reaction field (SCRF) approach has
been applied to the calculation of the solvent reorganization energy in self-exchange reactions. A series of redox couples,
O2/O−
2, NO/NO+, O3/O−
3, N3/N−
3, NO2/NO+
2, CO2/CO−
2, SO2/SO−
2, and ClO2/ClO−
2, as well as (CH2)2C-(-CH2-)
n
-C(CH2)2 (n=1 ∼ 3) model systems have been investigated using ab initio calculation. For these ET systems, solvent reorganization energies
have been estimated. Comparisons between our single-sphere approximation and the Marcus two-sphere model have also been made.
For the inner reorganization energies of inorganic redox couples, errors are found not larger than 15% when comparing our
SCRF results with those obtained from the experimental estimation. While for the (CH2)2C–(–CH2–)
n
–C(CH2)2 (n=1 ∼ 3) systems, the results reveal that the solvent reorganization energy strongly depends on the bridge length due to the
variation of the dipole moment of the ionic solute, and that solvent reorganization energies for different systems lead to
slightly different two-sphere radii.
Received: 19 April 2000 / Accepted: 6 July 2000 / Published online: 27 September 2000 相似文献
17.
C. Carnero Ruiz 《Colloid and polymer science》1999,277(7):701-707
The aggregation behaviour of tetradecyltrimethylammonium bromide in ethylene glycol–water mixtures across a range of temperatures
has been investigated by electrical conductivity measurements. The critical micelle concentration (cmc) and the degree of
counterion dissociation of micelles were obtained at each temperature from plots of differential conductivity, (κ/c)
T
,
P
, versus the square root of the total concentration of the surfactant. This procedure not only enables us to determine the
cmc values more precisely than the conventional method, based on plots of conductivity against total concentration of surfactant,
but also allows straightforward determination of the limiting molar conductance and the molar conductance of micellar species.
The equilibrium model of micelle formation was applied to obtain the thermodynamics parameters of micellization. Only small
differences have been observed in the standard molar Gibbs free energies of micellization over the temperature range investigated.
The enthalpy of micellization was found to be negative in all cases, and it showed a strong dependence on temperature in the
ethylene glycol poor solvent system. An enthalpy–entropy compensation effect was observed for all the systems, but whereas
the micellization of the surfactant in the solvent system with 20 wt% ethylene glycol seems to occur under the same structural
conditions as in pure water, in ethylene glycol rich mixtures the results suggest that the lower aggregation of the surfactant
is due to the minor cohesive energy of the solvent system in relation to water.
Received: 13 December 1998 Accepted in revised form: 25 February 1999 相似文献
18.
Erik Rakovsky ?udmila ?úrková Jaromír Marek 《Monatshefte für Chemie / Chemical Monthly》2002,22(2):277-283
Anhydrous 1,6-hexanediammonium dihydrogendecavanadate ((HdaH2)2H2V10O28, 1) was prepared by reaction of V2O5 with 1,6-hexanediamine in aqueous solution. The crystal structure of 1 was determined, and the proton positions in the H2V10O28 4− anion were calculated by the bond length/bond number method. The protons are bound to the centrosymmetrically oriented μ–OV3 groups of the decavanadate anion. Based on the analysis of IR spectra of 1 prepared from H2O and D2O, the absorption band at 871 cm−1 can be attributed to δ(V–Ob–H) vibrations. 相似文献
19.
Barthen N Millon E Aubriet F 《Journal of the American Society for Mass Spectrometry》2011,22(3):508-519
Laser ablation of titanium oxides at 355 nm and ion–molecule reactions between [(TiO2)x]–• cluster anions and H2O or O2 were investigated by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) with an external ion source.
The detected anions correspond to [(TiO2)x(H2O)yOH]– and [(TiO2)x(H2O)yO2]–• oxy-hydroxide species with x = 1 to 25 and y = 1, 2, or 3 and were formed by a two step process: (1) laser ablation, which
leads to the formation of [(TiO2)x]–• cluster anions as was previously reported, and (2) ion–molecule reactions during ion storage. Reactions of some [(TiO2)x]–• cluster anions with water and dioxygen conducted in the FTICR cell confirm this assessment. Tandem mass spectrometry experiments
were also performed in sustained off-resonance irradiation collision-induced dissociation (SORI-CID) mode. Three fragmentation
pathways were observed: (1) elimination of water molecules, (2) O2 loss for radical anions, and (3) fission of the cluster. Density functional theory (DFT) calculations were performed to explain
the experimental data. 相似文献
20.
Manufacturing of Saffil/MgLi metal matrix composites by the melt infiltration process is accompanied by extensive interfacial
redox reaction between δ-Al2O3 fibers (Saffil) and lithium. The present paper deals with the Fourier transform infrared spectroscopy examination of Saffil
fibers isolated from Mg–8 wt% Li alloy by the bromine/methylacetate agent focusing on the insertion of Li+ ions into δ-Al2O3 and their influence on water adsorption. Insertion of Li+ into δ-Al2O3 is monitored by gradual change of Al–O stretching bands (400–900 cm−1) towards more simple patterns of a spinel-like product assigned as δ(Li) which transforms to LiAl5O8 during subsequent annealing. Rapid increase in the water adsorption with increase in Li content, indicated by the changes
in H–O–H bending (about 1,650 cm−1) and O–H stretching (about 3,500 cm−1), is connected with the ionicity of the δ(Li) phase, which attracts polar water molecules. 相似文献