共查询到20条相似文献,搜索用时 0 毫秒
1.
Havazelet Bianco Moshe Narkis Yachin Cohen 《Journal of Polymer Science.Polymer Physics》1996,34(16):2775-2781
A small-angle X-ray scattering (SAXS) study of two-stage latices (TSL), composed of polystyrene (PS) and polytribromostyrene (PTBrS), is presented. The analysis of the scattering curves leads to the conclusion that the TSL particles have a concentric core-shell structure. When a PTBrS latex was used as a seed, its particles were overcoated with a PS shell during the second-stage polymerization. However, only a small portion of the seed particles were overcoated with a PTBrS shell when using a PS seed. The size distributions of the TSL and the PTBrS latex particles were determined from the scattering curves, using the method of Indirect Fourier Transformation. The resulting average radii were in good agreement with the values obtained from TEM observations. © 1996 John Wiley & Sons, Inc. 相似文献
2.
Lin Niu JingJing Yan XuYan Yang Christian Burger LiXia Rong Benjamin Hsiao DeHai Liang 《中国科学:化学(英文版)》2014,57(12):1738-1745
The phase behaviors of the complex formed by didodecyldimethylammonium bromide(DDAB)and cetyltrimethylammonium bromide(CTAB)interacting with three different types of DNAs,salmon testes DNA(~2000 bp),21-bp double-stranded oligonucleotides(oligo-ds DNA),and 21-nt single-stranded oligonucleotides(oligo-ss DNA)were studied by synchrotron small-angle X-ray scattering.It was found that the DNA length and flexibility,together with the positive/negative charge ratio,determined the final structure.At higher charge ratios,the DNA length exhibited negligible effect.Both oligo-ds DNA and salmon DNA formed inverted hexagonal packing of cylinders with CTAB,as well as bilayered lamella with DDAB.However,at lower charge ratios,oligo-ds DNA formed a distorted hexagonal phase with CTAB and a new structure with DDAB,which was different from the behaviors of salmon DNA.The flexible oligo-ss DNA formed rich structures that were subject to environmental disturbance.Kinetic study also indicated that the structures of the complex formed by oligo-ss DNA took much longer to mature than the structures formed by oligo-ds DNA.We attributed this result to the conformational adjustment of oligo-ss DNA in the complex. 相似文献
3.
The morphology of cold-drawn, rolled and annealed high-density polyethylene was investigated by transmission electron microscopy of stained sections. From the electron micrographs, a model of the structure was developed and the scattering pattern calculated. This was then compared with the corresponding small-angle X-ray scattering (SAXS) pattern, in order both to aid in the interpretation of SAXS patterns of oriented polymers, and to assess the effects of staining with chlorosulphonic acid on the morphology. 相似文献
4.
The assembly of colloidal particles in a nematic liquid crystal has been investigated using small-angle X-ray scattering. The structure and orientation of nanoparticle assemblies in bulk samples of aligned nematic liquid crystal have been determined. The method offers some advantages over optical microscopy, which is usually restricted to investigations of thin cells and micron-sized particles. The scattering from chains of particles has been calculated, and comparison with experimental results has shown that suspensions of 48 and 105 nm diameter silica nanoparticles formed highly ordered structures perpendicular to the liquid crystal director, consistent with quadrupolar defect-induced assembly. 相似文献
5.
Two models accounting for the changes of shape of the small-angle X-ray scattering (SAXS) curves during water adsorption by carbon adsorbents are discussed. The first model is based on the assumption of partial filling of the pore space; the second one presumes micropore swelling during water adsorption. Analysis of the results allows one to conclude that the first model is valid. This conclusion is in agreement with adsorption investigation data.Deseased 1993.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1220–1223, July, 1993. 相似文献
6.
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
7.
A. J. Ryan 《Journal of Thermal Analysis and Calorimetry》1993,40(3):887-899
The simultaneous SAXS/WAXD technique is shown to provide an unambiguous method for following structural changes taking place
during the programmed heating of a range of multiphase polymeric materials. Results are given for polyethylene, block copolyurethanes
and block copolyesters containing liquid crystalline hard segments.
UK Thermal methods Group Award Lecture 相似文献
8.
Jianling Zhang Dongxia Liu Guanying Yang Buxing Han Zhonghua Wu 《Colloid and polymer science》2007,285(11):1275-1279
Synchrotron small-angle X-ray scattering technique has been used to study the effect of ultrasound on the microstructure of
polystyrene (PS) in cyclohexane solutions. The results show that the intramolecular radius of gyration (R
g) decreases with ultrasound, indicating the shrinkage and collapse of PS chains. There is an exponential relationship between
R
g and the molecular weight of PS (M
w), and the exponent changes from 0.5 to 0.417, as the ultrasound time is increased. This means that the shape of PS chain
changes from random coil to shrunken form. The Kratky plots also confirm the shape transformation of PS chains induced by
ultrasound. Moreover, the intermolecular correlation length increases with the ultrasound time, which is indicative of the
entanglement of PS chains. 相似文献
9.
The development of the micropore structure of activated carbons during activation was studied by small-angle X-ray scattering and adsorption methods. A new method for the processing of experimental data was used; this method makes it possible to obtain curves of the dimension distribution of micropores from the intensities of small-angle X-ray scattering and the adsorption isotherm. In the initial stage of activation, up to burnouts 0.3, the micropore structure is uniform, micropores with radius of gyration under 0.5–0.6 nm dominate. When activation is more prolonged ( = 0.3÷0.67), a bimodal system withR
1
max 0.6 nm andR
2
max 0.85÷1.0 nm forms, and the volume of large micropores (supermicropores) exceeds that of small ones considerably.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 231–235, February, 1994. 相似文献
10.
The micellar radii and the electron density of the polar and non polar regions in micelles have been determined by a small-angle X-ray scattering (SAXS) technique originally designed by Luzzati et al. and subsequently modified by Larsson. The model employed shows the micellar structure as consisting of a liquid hydrocarbon core and a polar shell comprising the ionic polar head groups plus the diffuse double layer of bound counterions. The shortcomings of the model are discussed in the light of a recent paper by Hayter & Penfold providing general support for the parameters obtained and the conclusions drawn.The results found for the binary aqueous systems of potassium hexanoate, sodium octanoate and sodium decanoate describes the micelles as having quite an open structure with a rather small truly anhydrous hydrocarbon core. The low electron density contrast found between the polar layer and the surrounding media prevents us from drawing conclusions as to the absolute value of the polar (total) micellar radius, although the changes in this radius seem relevant. The octane-1, 8-diol is found to partly penetrate the hydrocarbon core but mostly to reside in the polar shell or to remain in the bulk solvent. Both the cyclohexane and carbon tetrachloride seem to be solubilized in the interior of the micelle, the former causing a considerable swelling of the micelle. 相似文献
11.
Peter Zipper Manfred Kriechbaum Rudolf Wilfing Helmut Durchschlag 《Monatshefte für Chemie / Chemical Monthly》1986,117(5):557-572
The X-ray induced aggregation of the sulfhydryl enzyme malate synthase in aqueous solution was monitoredin situ by time-resolved small-angle X-ray scattering. Experiments were performed in the absence/presence of various additives: formate, superoxide dismutase, catalase, NaCl, acetyl-CoA, glyoxylate, malate, pyruvate, -ketobutyrate, oxaloacetate, glycollate, lactate. The scattering curves were measured as a function of the time of irradiation and were analysed in terms of radii of gyration, degrees of aggregation, distance distribution functions, and parameters derived therefrom. Irradiation in the absence of additives resulted in a strong aggregation of enzyme particles. Each of the additives impeded aggregation, however to a different extent. The OH scavenger formate reduced aggregation efficiently; less pronounced effects were registered for superoxide dismutase and/or catalase (the scavengers for
and H2O2), and for NaCl. Very pronounced diminutions of the aggregation phenomena were provided by substrates or analogues; the efficiency of these substances as radioprotectors may be explained by their action as both scavengers and specific ligands. Based on these results some implications for the performance of conventional small-angle X-ray scattering experiments on biopolymers are derived.
Der Einfluß von Zusätzen auf die röntgeninduzierte Aggregation der Malatsynthase. Registrierung des Aggregationsvorganges in situ mittels zeitaufgelöster Röntgenkleinwinkelstreuung
Zusammenfassung Die röntgeninduzierte Aggregation des Sulfhydrylenzyms Malatsynthase in wäßriger Lösung wurdein situ mittels zeitaufgelöster Röntgenkleinwinkelstreuung messend verfolgt. Streuexperimente wurden in An- bzw. Abwesenheit verschiedener Zusätze durchgeführt: Formiat, Superoxiddismutase, Catalase, NaCl, Acetyl-CoA, Glyoxylat, Malat, Pyruvat, -Ketobutyrat, Oxalacetat, Glycolat, Lactat. Die Streukurven wurden als Funktion der Bestrahlungsdauer registriert. Die Auswertung lieferte Streumassenradien, Aggregationsgrade, Abstandsverteilungsfunktionen, und daraus abgeleitete Parameter. Die Bestrahlung in Abwesenheit von Zusätzen verursachte eine starke Aggregation der Enzymteilchen. Jeder der Zusätze verminderte die Aggregation, wenn auch in unterschiedlichem Ausmaß. Der OH Fänger Formiat verringerte die Aggregation wirksam; weniger stark ausgeprägte Effekte ergaben sich für die bzw. H2O2 Fänger Superoxiddismutase bzw. Catalase und für NaCl. Substrate und Substratanaloge reduzierten das Ausmaß der Aggregation besonders wirkungsvoll; der Schutzeffekt dieser Substanzen kann durch ihre zweifache Wirkung als Fänger bzw. spezifische Liganden erklärt werden. Ausgehend von diesen Ergebnissen werden einige Schlußfolgerungen für die Durchführung üblicher Röntgenkleinwinkelexperimente an Biopolymeren abgeleitet.相似文献
12.
13.
N. S. Murthy C. Bednarczyk R. A. F. Moore D. T. Grubb 《Journal of Polymer Science.Polymer Physics》1996,34(5):821-835
The changes in the fibrillar and the lamellar structure in nylon 6 fibers resulting from drawing and annealing were studied by a detailed analysis of their two-dimensional small-angle scattering patterns. The scattering object that gives to rise the diffuse equatorial scattering in the angular range of Q = 0.02 to 0.3 Å−1 is assumed to be a fibril. There are two distinct regimes in the equatorial diffuse scattering. The scattering at Q < 0.1 Å−1 is dominated by scattering due to the longitudinal dimension of the fibril, and that at Q > 0.1 Å−1 to the lateral dimensions/organization of the fibril. The interfibrillar regions, unlike the interlamellar regions that are essentially made of amorphous chain segments, may have microvoids in addition to amorphous chain segments. The intensity distribution within the lamellar reflections was used to obtain the lamellar spacings and the dimension of the lamellar stacks. The length of the fibrils is between 1000 and 3000 Å, the higher values being more prevalent at lower draw ratios. The fibril length is larger than the length of the lamellar stack, and approaches the latter at higher draw ratios. Annealing does not change the lengths of the fibrils, but the length of the lamellar stack increases. The fibrils form crystalline aggregates with a coherence length of ∼200 Å at higher draw ratios. The diameter of the fibrils (50–100 Å) determined from the lamellar reflection using both the Scherrer equation and the Guinier law are consistent with the lateral size of the crystallites derived from wide-angle x-ray diffraction. The longitudinal correlation of the lamellae between the neighboring fibrils improves upon drawing and decreases upon annealing. The degree of fibrillar and lamellar orientation is about the same as the crystalline orientation. Lamellar spacing increases upon drawing (from ∼60 to 95 Å) and annealing (from ∼85 to 100 Å). This is accompanied by an increase in the width of the amorphous domains from 30 to 50 Å in drawn fibers, and from 45 to 55 Å in annealed fibers. The diameter of the fibrils decreases slightly upon drawing and increases considerably upon annealing. © 1996 John Wiley & Sons, Inc. 相似文献
14.
Junko Konishi Koji Fujita Kazuki Nakanishi Shotaro Nishitsuji Mikihito Takenaka Kiyotaka Miura Kazuyuki Hirao 《Journal of Sol-Gel Science and Technology》2008,46(1):63-69
Titania (TiO2) monoliths with well-defined bicontinuous macropores and gel skeletons were prepared through the alkoxy-derived sol–gel process
accompanied by spinodal decomposition, and the structural evolution during evaporation drying and heat treatment was probed
by a combination of ultra-small-angle X-ray scattering and small-angle X-ray scattering. X-ray scattering profiles of wet
and dried gels revealed that microporous structures related to the existence of primary particles are present in the gel skeletons
at the wet stage and are preserved during drying. Additionally, it is found that the primary particles swollen in the wet
condition are dried to compact aggregates to produce the smooth surface of gel skeletons. Upon heating at 400 °C, the particle–particle
correlation associated with regularity of mesostructures is enhanced. From nitrogen adsorption–desorption measurements, the
average pore size is less than 1 nm in the dried gel and increases to 3.1 nm by the heat treatment. Homogeneous growth of
primary particles due to interparticle-polycondensation reaction is responsible for the increased size and uniform distribution
of mesopores in the heat-treated gel. 相似文献
15.
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
16.
Static and quasielastic light-scattering measurements of endsulfonated polyisoprene in a water in oil (w/o) microemulsions were used to characterize the structure and diffusion properties of this complex system. The hydrophilic end groups of the polymer stick to the surfactant covered oil/water interface, thus bridging the water droplets. This structure formation decreases the mobility of the aqueous nanodroplets and polymer molecules. At interdroplet distances larger than the end-to-end distance of the ionomer chain a decrease of the osmotic modulus is observed. It can be explained by a depletion force of free ionomer chains acting on the nanodroplets. With increasing polymer concentration structure formation of the microemulsion is observed at nanodroplet concentrations where the ionomer chains just fit the average separation of two nanodroplets. 相似文献
17.
Phase separation that takes place during the formation of semi-interpenetrating polymer networks based on crosslinked polyurethane and linear polystyrene was studied by small-angle X-ray scattering and light scattering. The kinetics of the chemical reactions was followed by Fourier transform infrared spectroscopy. The occurrence of broad peaks in the X-ray scattering curves was interpreted in terms of distances between the urethane crosslinks. Small modulations on these curves were assigned to sphere-like structures with a diameter of around 5 nm which might be related to the urethane crosslink regions. Small modulations on the light-scattering curves at the beginning of styrene polymerization were assigned to spheres with diameters of around 4.5 μm, which can be related to the polystyrene-rich phase. These modulations disappear with time, which might indicate an increasing polydispersity of the domain sizes. The final morphology was found to depend on the time at which polymerization of styrene is initiated with respect to the time of gelation of polyurethane. 相似文献
18.
A procedure of analysis for small-angle X-ray scattering (SAXS) data has been established to obtain density fluctuation of supercritical fluids near the critical point. It is indispensable for the certain analysis to utilize both of high-quality SAXS data measured under stable thermodynamic condition and accurate P–ρ–T data in supercritical region. As a standard example, SAXS measurements have been performed for supercritical CO2, which is a suitable sample satisfying the condition for both experiment and analysis. The measurements were carried out along four isothermal conditions at reduced temperature of Tr = T/Tc = 1.020, 1.022, 1.043 and 1.064. Comparing the experimental density fluctuation with calculated one from the most reliable equation of state, the differences are within 8% at most. 相似文献
19.
Dvora Perahia Xuesong Jiao Rakchart Traiphol 《Journal of polymer science. Part A, Polymer chemistry》2004,42(17):3165-3178
Small-angle neutron scattering has been used to study the conformation and structure of highly interacting macromolecules in complex fluids. The evolution of the structure has been investigated from the conformation of a single molecule through an association process to the formation of physical networks. Two highly interacting polymers, an ionic polymer (consisting of a perfluorinated backbone and an ionizable hydrophilic side chain dissolved in water/alcohol mixtures) and rodlike, highly conjugated phenylene ethylene molecules (dissolved in toluene), have been studied. Highly interacting polymers often form relatively long lasting physical networks with increasing polymer concentration. The driving force, however, is system-specific, and so are the micellar systems and physical networks formed. Although the two families of polymers under consideration are entirely different chemically, their strong interaction, either ionic or through π–π coupling, results in similarities in the complex fluids formed when they are dissolved in solutions. These include elongated configurations in dilute solutions, association into micelles, and eventually coalescence into physical networks. The ionic polymers form durable stable networks, whereas the rodlike polymers form a fragile, gel-like phase. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3165–3178, 2004 相似文献
20.
Erkan Senses Christopher L. Kitchens Antonio Faraone 《Journal of polymer science. Part A, Polymer chemistry》2022,60(7):1130-1150
The addition of nanoparticles to a polymer matrix can in certain cases induce a reduction in viscosity, with respect to the pure matrix, in the resulting composites. This counterintuitive phenomenon cannot be explained using the most common rheological models. For this reason, it has been chosen as a good example in this paper to demonstrate the value and methods of dynamic X-ray and neutron scattering techniques for the investigation of polymer nanocomposites. An overview of the main results on this topic is presented together with an introduction to the basic concepts relating to X-ray photon correlation spectroscopy, neutron backscattering, and neutron spin echo measurements. 相似文献