共查询到20条相似文献,搜索用时 31 毫秒
1.
A small-angle x-ray scattering (SAXS) study of latex particles consisting of a polystyrene (PS) core and a polymethylmethacrylate (PMMA) shell in theq-range 0.037 nm–1q1.5 nm–1 (q=(4/) sin (/2); : scattering angle) is reported. The particle size distributions of the latices have been determined by ultracentrifugation and allow a quantitative comparison of the experimental scattering intensities with theoretical models. The data obtained for the PS/PMMA latex are shown to be consistent with the proposed core-shell morphology. Separate studies of the PS-core-latex demonstrate that the amount of surfactant being adsorbed on the surface of the particles can be monitored directly. All results show that SAXS is well-suited to study the structure of latex particles in great detail. 相似文献
2.
We report the evidence for attractive interaction of latex particles which are covered by poly(ethylene oxide) chains. These
particles are suspended in aqueous solutions of ammonium sulfate. The interaction is probed by measurements of the turbidity
of the suspensions up to 70 g/l. Turbidity is insensitive to multiple scattering and allows the static structure factor, S(q) [q=(4πn
0/λ0)sin(θ/2), where θ is the scattering angle, n0 is the refractive index of the medium and λ0 is the wavelength in vacuo], to be determined at small q values. The analysis of S(q) at small q values yields information about possible attraction of the particles. The analysis of the turbidity data furthermore shows
that no aggregation took place in these systems. A weak but long-range attractive interaction was found at ammonium sulfate
concentrations of 0.01 and 0.1 M. The relation of this attractive force to hydrophobic forces is discussed.
Received: 9 March 2000/Accepted: 28 June 2000 相似文献
3.
The self-assembling structures and dynamics of surfactants determine most of their macroscopic physicochemical properties and performances. Herein, we review recent work on the self-assembly of surfactants by small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) in conjunction with cryogenic transmission electron microscopy (Cryo-TEM) from the perspective of researchers having only limited theoretical knowledge of these techniques but expert in surfactants. Emphasis is placed on the structural analysis of typical surfactant aggregates over a wide range of size scales from nanometers up to microns, including spherical and rod-like micelles, wormlike micelles, vesicles, liquid crystals and coacervates, by combining different numerical approaches to the treatment of small-angle scattering data with the direct Cryo-TEM imaging method. Furthermore, the complementarity between SAXS and SANS, and between the scattering techniques and Cryo-TEM, that is, specific contributions of these techniques, is also covered. 相似文献
4.
A new small-angle light scattering camera has been developed. In contrast to conventional detection the present system is
based on a recently developed two-dimensional charge-coupled-device chip made by Thomson (France). The advantage of this chip
is its excellent linear response and very low dark signal even at room temperature. The best linearity was obtained by leading
each pixel signal through the same amplifying system. The optical system covered a diffraction angular region from about 1°
to 15° (q = 0.2–2.6 μm−1). The camera was calibrated with grids and pinholes and was tested with polymer latex particles in solution and with spherulites
from polymer films.
Received: 06 December 1999 Accepted: 04 February 2000 相似文献
5.
O. G. Us’yarov 《Colloid Journal》2016,78(5):698-704
The small-angle X-ray scattering (SAXS) in micellar sodium dodecyl sulfate solutions has been studied in the range of overall concentrations c from 8 mM (CMC1) to 300 mM and the absolute values of scattering vector q from 0.07 to 3.0 nm–1. The total intensity of isotropic scattering has been revealed to increase with solution concentration. At c > 27 mM, the SAXS spectra have been found to exhibit an interference peak, which testifies a correlation in the arrangement of micelles in the bulk solution. This peak corresponds to the magnitude of q close to 1.55 nm–1. Using the position of this maximum, average distance r0 between the centers of micelles has been determined, which is equal to 4.1 nm and remains almost unchanged upon an increase in the overall concentration of sodium dodecyl sulfate. The observed regularities have been explained in terms of the DLVO theory taking into account the electrostatic and molecular intermicellar interaction. 相似文献
6.
The molecular order and phase transitions of two smectic poly(ester imide)s based on aminobenzoic acid trimellitimide (PEI
1) or aminocinnamic acid trimellitimide (PEI 2) and α,ω-dihydroxydodecane were investigated by X-ray scattering. During cooling,
the polymers pass through monotropic smectic liquid-crystalline (LC) phases (SA, SC), which transform into higher-ordered smectic-crystalline phases (SE, SH). The smectic layer structure of about 3 nm gives rise to a sharp reflection at 2θ ≅ 3°. Peak shape analysis and analysis
of the interface distribution function revealed long-range longitudinal correlation among the mesogens in the LC phase but
short-range lateral correlation. The development of a broad reflection in the small-angle X-ray scattering (SAXS, 2θ < 1°)
indicates the formation of a lamellar two-phase system. The long-period changes reversibly between 10 and 30 nm with increasing
temperature. The crystalline lamellae comprise a number of smectic-crystalline layers with packed mesogens, while the noncrystalline
interlamellar regions keep their smectic-LC order. In the metastable SB phase, formed during annealing of quenched PEI 1, the diffuse SAXS indicates a random distribution of small, probably fringed,
crystals with hexagonal-packed mesogens. In the lamellar SE and SH phases, tie molecules play an important role, but chain folding cannot be excluded.
Received: 16 July 1999/Accepted: 28 April 2000 相似文献
7.
《Current Opinion in Colloid & Interface Science》2001,6(2):132-139
The analysis of latex particles by small-angle scattering (small-angle X-ray scattering, SAXS; small-angle neutron scattering, SANS) is reviewed. Small-angle scattering techniques give information on the radial structure of the particles as well as on their spatial correlation. Recent progress in instrumentation allows to extend SANS and SAXS to the q-range of light scattering. Moreover, contrast variation employed in SANS and SAXS studies may lead to an unambiguous determination of the radial scattering length density of the particles in situ, i.e. in suspension. Hence, these techniques are highly valuable for a comprehensive analysis of polymer colloids as shown by the examples discussed herein. 相似文献
8.
Growth process for fractal polymer aggregates formed by perfluorooctyltrimethoxysilane. Time-resolved small-angle X-ray scattering study 总被引:1,自引:0,他引:1
T. Ogasawara K. Izawa N. Hattori H. Okabayashi C. J. O'Connor 《Colloid and polymer science》2000,278(4):293-300
The acid-catalyzed condensation reaction of perfluorooctyltrimethoxysilane (PFOS) and n-octyltrimethoxysilane (OTMS) in ethanol has been followed by time-resolved synchrotron radiation small-angle X-ray scattering
(SAXS) on a short time scale. SAXS curves for PFOS and OTMS have been interpreted as arising from mass fractals with D
f=2 (PFOS) and D
f=1.7 (OTMS). The time dependence of the apparent radius of gyration, obtained from the Guinier plots, showed that the growth
of fractal precursors occurs in a two-step process within 2 h for PFOS and within 1.5 h for OTMS, in which small clusters
involving monomers, dimers and trimers are formed in the initial step and formation of larger clusters occurs in the second
step. Furthermore, it has been suggested that the hydrophobicity and lipophobicity of the bulky alkyl groups may also contribute
to the formation of these giant aggregates.
Received: 13 July 1999/Accepted in revised form: 6 October 1999 相似文献
9.
Nilesh M. Vaghela Nandhibatla V. Sastry Vinod K. Aswal 《Colloid and polymer science》2011,289(3):309-322
The surface active and aggregation behavior of ionic liquids of type [C
n
mim][X] (1-alkyl-3-methylimidazolium (mim) halides), where n = 4, 6, 8 and [X] = Cl−, Br− and I− was investigated by using three techniques: surface tension, 1H nuclear magnetic resonance (NMR) spectroscopy, small-angle neutron scattering (SANS). A series of parameters including critical
aggregation concentrations (CAC), surface active parameters and thermodynamic parameters of aggregation were calculated. The
1H NMR chemical shifts and SANS measurements reveal no evidence of aggregates for the short-chain 1-butylmim halides in water
and however small oblate ellipsoidal shaped aggregates are formed by ionic liquids with 1-hexyl and 1-octyl chains. Analysis
of SANS data analysis at higher concentrations of [C8mim][Cl] showed that the microstructures consist of cubically packed molecules probably through π–π and hydrogen bond interactions. 相似文献
10.
H. Etori H. Hirata Y. Yamada H. Okabayashi M. Furusaka 《Colloid and polymer science》1997,275(3):263-273
Potassium salts of N-decanoylglycine and N-decanoyl-L-alanine oligopeptides (monomer, dimer and trimer) were synthesized.
For these oligomer salts in aqueous solutions, the microstructures of micelles have been investigated by small-angle neutron-scattering
(SANS). In the calculation of SANS intensity data, the thickness of the hydrophilic layer was altered by changing the conformation
of the oligomer moiety (helical and β-sheet structures). For micelles of the trimer salts, the helical structure models provide
the best fit to the observed SANS intensity data. For micelles of the monomer-and dimer-salts, the β-sheet model provides
the best fit to the observed data. For the monomer-and dimer-micelles, the aggregation number (n) is not dependent on the species of amino acid residue, imply-ing that the decanoyl group plays a critical role in micelle
formation. However, for the trimer micelles, the n value is dependent on the species of amino acid residue.
Received: 11 July 1996 Accepted: 11 September 1996 相似文献
11.
Sommer C Pedersen JS Garamus VM 《Langmuir : the ACS journal of surfaces and colloids》2005,21(6):2137-2149
Spherical micelles of the diblock copolymer/surfactant Brij 700 (C(18)EO(100)) in water (D(2)O) solution have been investigated by small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS). SAXS and SANS experiments are combined to obtain complementary information from the two different contrast conditions of the two techniques. Solutions in a concentration range from 0.25 to 10 wt % and at temperatures from 10 to 80 degrees C have been investigated. The data have been analyzed on absolute scale using a model based on Monte Carlo simulations, where the micelles have a spherical homogeneous core with a graded interface surrounded by a corona of self-avoiding, semiflexible interacting chains. SANS and SAXS data were fitted simultaneously, which allows one to obtain extensive quantitative information on the structure and profile of the core and corona, the chain interactions, and the concentration effects. The model describes the scattering data very well, when part of the EO chains are taken as a "background"contribution belonging to the solvent. The effect of this becomes non-negligible at polymer concentrations as low as 2 wt %, where overlap of the micellar coronas sets in. The results from the analysis on the micellar structure, interchain interactions, and structure factor effects are all consistent with a decrease in solvent quality of water for the PEO block as the theta temperature of PEO is approached. 相似文献
12.
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
13.
14.
Jon Samseth Richard J. Spontak Kell Mortensen 《Journal of Polymer Science.Polymer Physics》1993,31(4):467-474
Poly(siloxaneimide) (PSI) segmented copolymers exhibit organized microdomains if the blocks are sufficiently incompatible. As with neat diblock and triblock copolymers, the processing route employed to prepare films of PSI materials is expected to influence the dimensions and/or morphology of the resultant microstructure. In this work, small-angle neutron scattering (SANS) is utilized to characterize the disordered microstructure found in films of a series of PSI copolymers which are subjected to solvent casting and various thermal treatments. Microstructural dimensions such as the periodicity and correlation length are deduced from the Teubner-Strey (TS) model for disordered microemulsions. The scattering intensity of each copolymer up to q = 5.0 nm?1, where q is the scattering vector, is found to scale as q?2.8+?0.1. Results indicate that processing the materials as cast films or as melt-pressed films allowed to cool slowly has a small, but discernible, effect on microstructural characteristics. SANS profiles of films quenched from elevated temperatures reveal a clear transition in microdomain periodicity, which correlates well with the glass transition temperature of the imide microphase in these and other materials of similar chemical structure. © 1993 John Wiley & Sons, Inc. 相似文献
15.
3]2+. Whereas the initial method is carried out in an aqueous solution, the improved one employs an aqueous micellar medium formed
by the cationic surfactant cetylpyridinium bromide (CPBR). The λmax in both methods is the same, i.e. 510 nm. The mean apparent
molar absorptivity (ɛ) and Sandell’s sensitivity (Ss) were calculated as ɛ=2.10×104 Lmol-1 cm-1 and Ss=8.37 ng cm-2 for the initial procedure, and ɛ=2.62×104 Lmol-1 cm-1 and Ss=6.72 ng cm-2 for the improved one. The regression line equation for the improved method was: A=1.487×10-1C −1.415×10-2 (r=0.9998). The accuracy and the precision of the improved method were investigated and the conclusions were satisfactory.
The results obtained for ASCA by both the described method and an official one, were statistically compared by means of the
Student’s t-test and by the variance ratio F-test; and no significant difference was observed.
Received: 15 January 1996/Revised: 7 March 1996/Accepted: 13 March 1996 相似文献
16.
R. Beck M. Gradzielski K. Horbaschek S. S. Shah H. Hoffmann P. Strunz 《Colloid and polymer science》2000,278(2):137-142
The phase behaviour and properties of the tetradecyldimethylamine oxide/HCl/hexanol/water quaternary surfactant system have
been studied by means of electric conductivity, rheology, freeze-fracture transmission electron microscopy (FF-TEM) and small-angle
neutron scattering (SANS). In this system the originally zwitterionic surfactant can become increasingly charged by protonation
through the addition of HCl, i.e. the degree of charging can be changed continuously. An interesting, isotropic phase (L1
* phase) of low viscosity was observed for intermediate degrees of charging. From viscosity and conductivity measurements this
phase can clearly be distinguished from the conventional L1 phase that is composed of micelles. Investigation of the structures present by means of FF-TEM and SANS showed that the L1
* phase is made up of unilamellar vesicles of extremely small diameter of 8–10 nm. Evidently such highly curved structures
are stabilized by the electrostatic conditions in this system.
Received: 11 July 1999/Accepted: 25 August 1999 相似文献
17.
The numerical properties of the radial part of overlap integrals with the same screening parameters in the form of polynomials
in p = ξR over Slater-type orbitals have been studied and obtained by using three different methods. For that purpose, the characteristics
of auxiliary functions were used first, then Fourier transform convolution theorem, and recurrence relations for the basic
coefficients of A
s
n
l
λ,
n
′
l
′λ were used. The calculations of the radial part of overlap integrals with the same screening parameters were made in the range
1 ≤ n ≤ 75, 1 ≤ n′ ≤ 75, and 10−6 ≤ p.
Received: 18 January 2001 / Accepted: 5 April 2001 / Published online: 27 June 2001 相似文献
18.
I. Shimizu H. Okabayashi N. Hattori K. Taga A. Yoshino C. J. O’Connor 《Colloid and polymer science》1997,275(3):293-297
Changes in the 13C and 1H NMR chemical shifts of the silane coupling agent (3-aminopropyltri-ethoxysilane, APTS) in toluene, which were detected as
the concentration of APTS increased, have been interpreted in terms of the formation of micelles and the presence of a critical
micelle concentration (CMC) equal to ca. 0.47 mol 1-1. For the protons of the n-propyl segment, 1H NMR splitting patterns have been analyzed and conformations of the propyl segment have been discussed. Plots of relative
absorbance of the two NH2 stretch IR bands at 3324 and 3384 cm-1 against concentration provided an inflection point (corresponding to the CMC) at a value equal to 0.46 mol 1-1. Thus, consideration of the interaction of APTS with a surface must take into account the presence of both APTS aggregates
as well as APTS monomers.
Received: 16 August 1996 Accepted: 26 September 1996 相似文献
19.
B. Guilleaume M. Ballauff G. Goerigk M. Wittemann M. Rehahn 《Colloid and polymer science》2001,279(9):829-835
We consider the analysis of a rodlike synthetic polyelectrolyte in solution by anomalous small-angle X-ray scattering (ASAXS)
in order to elucidate the correlation of the counterions with the highly charged macroion. ASAXS can be applied to these systems
because the absorption edge of typical counterions, for example, bromine or iodine ions can be attained by synchrotron radiation.
Model calculations using the Poisson–Boltzmann cell model show that ASAXS furnishes two terms caused by the anomalous dispersion
of the counterions. The leading terms is a cross-term between the ordinary scattering amplitude of the polyelectrolyte and
the real part of the scattering length f ′ of the counterions. A second term refers solely to the anomalous contribution of the counterions, i.e., to f ′ and f ′′ ( f ′′: imaginary part of scattering length). Preliminary data obtained from rodlike synthetic macroions having iodine counterions
corroborate the theoretical deductions. They demonstrate that ASAXS is capable of furnishing information that is not available
by the ordinary SAXS experiment.
Received: 11 December 2000/Accepted: 22 February 2001 相似文献
20.
Vernhet A Dubascoux S Cabane B Fulcrand H Dubreucq E Poncet-Legrand C 《Analytical and bioanalytical chemistry》2011,401(5):1563-1573
Condensed tannins are a major class of plant polyphenols. They play an important part in the colour and taste of foods and
beverages. Due to their chemical reactivity, tannins are not stable once extracted from plants. A number of chemical reactions
can take place, leading to structural changes of the native structures to give so-called derived tannins and pigments. This
paper compares results obtained on native and oxidized tannins with different techniques: depolymerization followed by high-performance
liquid chromatography analysis, small-angle X-ray scattering (SAXS) and asymmetric flow field-flow fractionation (AF4). Upon
oxidation, new macromolecules were formed. Thioglycolysis experiments showed no evidence of molecular weight increase, but
thioglycolysis yields drastically decreased. When oxidation was performed at high concentration (e.g., 10 g L−1), the weight average degree of polymerization determined from SAXS increased, whereas it remained stable when oxidation was
done at low concentration (0.1 g L−1), indicating that the reaction was intramolecular, yet the conformations were different. Differences in terms of solubility
were observed; ethanol being a better solvent than water. We also separated soluble and non-water-soluble species of a much
oxidized fraction. Thioglycolysis showed no big differences between the two fractions, whereas SAXS and AF4 showed that insoluble
macromolecules have a weight average molecular weight ten times higher than the soluble ones. 相似文献