Synchrotron X-ray Scattering Research Articles

Synchrotron X-Ray Scattering Studies of the Surface Structure and Dynamics of Liquids and Liquid Films

AbstractThe dynamics of surface fluctuations in thin supported polystyrene films have been investigated using x-ray photon correlation spectroscopy (XPCS) in reflection geometry. The results from the films thicker than four times of the radius of gyration (Rg) of polystyrene show the behavior of the capillary waves expected in viscous liquid. However, thinner films show a deviation indicating the need to account for viscoelasticity. Theoretical considerations with viscoelastic liquid model has been performed by introducing frequency dependent viscosity and compared with Fredrickson’s brush model (Macromolecules, 25, 2882 (1992)). The theory has been extended to the surface and interfacial modes in a bilayer film system. The results will be discussed in terms of surface tension, viscosity, and shear modulus.

Studies of the structure and growth mode of dotriacontane films by synchrotron x-rayscattering and molecular dynamics simulations

We report on synchrotron x-ray scattering experiments and moleculardynamics simulations of the structure and growth mode of dotriacontane(n-C32H66 or C32) films adsorbedon Ag(111) and SiO2-coatedSi(100) substrates. On the SiO2 surface, the x-ray measurements confirm a structural model of the solid film inferred fromhigh-resolution ellipsometry measurements in which one or two layers of C32 adsorb withthe long axis of the molecule oriented parallel to the interface followed by a monolayer inwhich the molecules have a perpendicular orientation. At higher C32 coverages,preferentially oriented bulk particles nucleate, consistent with a Stranski–Krastanov growthmode. On the Ag(111) surface, we again observe one or two layers of the ‘parallel’ film butno evidence of the perpendicular monolayer before nucleation of the preferentiallyoriented bulk particles. We compare the experimentally observed structures withmolecular dynamics simulations of a multilayer film of the homologous C24 molecule.

Time-Resolved Synchrotron X-ray Scattering of the Crystallization of a Soft Hexagonal Columnar Crystal

We have recently shown (Langmuir 2000, 16, 5846) that a soft surfactant hexagonal phase exhibits, above a critical shear rate, a shear-melting transition, where a two-dimensional polycrystalline texture is converted into a liquid of rods aligned along the flow. Moreover, after abrupt cessation of high shear, a monocrystal-like structure is obtained. In this paper, we investigate the kinetics of crystallization from the shear-melted phase by means of time-resolved synchrotron X-ray scattering experiments. After a latency time, the sample is found to continuously evolve from a liquid of rods to a monocrystal of rods. We show that the crystallization results from a coupling between bulk crystallization and interfacial crystallization, due to a specific anchoring of the liquid crystal at the walls of the shear cell. A detailed analysis of the experimental data allows the evaluation of the propagation of the interfacial front and the time evolution of the size of the crystallites. We find that the size scales as t(v) with v approximately equal to 0.3, in fair agreement with recent theories and simulations on grain rotation-induced grain growth of columnar polycrystalline structures.

Synchrotron X-ray Scattering and Precise Structural Analyses of Poly(ethylene terephthalate) Fibers Prepared by High Speed Melt Spinning

Precise structural analyses of high speed melt spinning fibers provide useful information of appropriate nano-structures for imparting ultra-high strength to general fibers. For quantitative and precise analyses by X-ray scattering measurements, strong X-ray source is required. In this paper, we demonstrate significance of the synchrotron X-ray scattering and precise structural analyses of poly(ethylene terephthalate) fibers prepared by high speed melt spinning, with the take-up velocity ranging 1∼9 km/min. Systematic changes in the 2d-SAXS (two-dimensional small-angle X-ray scattering) patterns were clearly observed as a function of the take-up velocity. For 3 km/min, only streaks on the equator were distinct. For 4∼6 km/min, characteristic X-shaped cross-streaks appeared with the streaks on the equator. Then, at 7∼9 km/min, a pair of broad streaked peaks parallel to the equator appeared instead of the cross-streaks, while the equatorial streaks still coexist. We ascribed the X-shaped cross-streaks to a zig-zag fibril structure, and the equatorial streaks with the broad streaked peaks to a shish-kebab structure. Then, based on the 2d-SAXS results, change in the fiber structures with an increase of the take-up velocity is considered. For 4∼6 km/min, the zig-zag fibril is dominant. However, a trivial amount of shish seems to coexist. The shape of fibril changed from zig-zag to straight with an increase of the take-up velocity, while the shish-kebab fraction was considered to increase. It is noted here that the zig-zag fibril consists of somewhat different from an ordinary fibril, but rather thicker-and-looser agglomerates of crystallites. At 9 km/min, fibril is no more the zig-zag, but a straight shish, with a well-developed kebab structure.

In Situ Radial Small Angle Synchrotron X-ray Scattering Study of Shear-Induced Macroscopic Orientation of Hierarchically Structured Comb-Shaped Supramolecules

Laboratory of Polymer Chemistry, Materials Science Centre,Dutch Polymer Institute, University of Groningen,Nijenborgh 4, 9747 AG Groningen, The Netherlands,NWO, DUBBLE CRG/ESRF, c/o BP 220 Grenoble F38043,France, and Department of Engineering Physics andMathematics and Center for New Materials,Helsinki University of Technology, P.O. Box 2200,FIN-02015 HUT, Espoo, FinlandReceived October 21, 2002Revised Manuscript Received January 9, 2003

Shear-Induced Structure in Concentrated Dispersions: Small Angle Synchrotron X-ray and Neutron Scattering

The influence of shear on the Bragg scattering of concentrated colloidal dispersions made from charged particles is considered in this paper. First, the reciprocal space of a layered sample at rest and under the influence of a disordering torque is considered. Next, the commonly used Couette cell and our disk shear cell are compared in view of the Ewald construction. An introduction of α- and β-rotation axes follows. The first experimental example is concerned with the neutron scattering from a layered colloidal sample at rest. As a second experimental example from the same sample the dependence of synchrotron X-ray scattering on the shear rate is considered. It turns out that the sample does not achieve a microcrystalline state as claimed previously but remains in an orientationally disordered layered state. Finally, the intensity distribution I(l) along the two types of Bragg rods as obtained with remarkable precision by synchrotron X-ray scattering is presented.

Lyotropic Phase Transitions in Phospholipids as Evidenced by Small-Angle Synchrotron X-Ray Scattering

Hydration is an important factor in regulating the phase behaviour of lipids and besides affects their interactions with other compounds relevant for biological membranes. We present a reliable and fast method to detect and characterise hydration-induced phase transitions in phospholipids by means of small-angle synchrotron X-ray scattering. Films consisting of aggregations of representatives of the two important lipid classes lecithins (DPPC a, POPC and OPPC, a for abbreviations, see below) and cephalins (DPPE and DOPE) were investigated at room temperature in dependence on relative humidity. Qualitative changes in the sets of the diffraction patterns obtained in dynamic hydration/dehydration scans were taken as markers indicating the existence of lyotropic phase transitions. The efficiency of this methodology is demonstrated by illustrating the course of hydration-driven phase transitions between lamellar as well as nonlamellar phases. In detail, this was realised for chain melting in the mixed-chain lipids, POPC and OPPC, and for a novel nonlamellar-phase transition for DOPE between a disordered inverted ribbon phase designated as Pα and the canonical HII phase, respectively.

Morphological Changes During Crystallization and Melting of Polyoxymethylene Studied by Synchrotron X-Ray Scattering and Modulated Differential Scanning Calorimetry

Temperature scanning techniques, including synchrotron small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction(WAXD), and temperature-modulated differential scanning calorimetry (TMDSC), were used to study melting recrystallization in semicrystalline polyoxymethylene (POM). The isothermal crystallization of POM was also studied by time-resolved SAXS. From SAXS profiles, several morphological variables were calculated, including the long period L, lamellar thickness lc , interlamellar amorphous thickness la , and scattering invariant Q. The lamellar parameters were also obtained using tapping atomic force microscopy (AFM) for two thermal histories, and some lamellar-scale and larger-scale morphological changes were characterized before and after partial melting. These real-space images also provided support to interpretation of SAXS analysis in the interpretation of first- and second-order intensity maxima. During melting at constant heating rates, la from SAXS increased slowly starting at about 100°C, suggesting melting of thin inserted lamellae, and at about 150°C, lc began to increase combined with a more rapid increase in la due to further melting of inserted lamellae and some recrystallization into separate stacks of lamellae. The end of melting was about 182°C. TMDSC data also characterized the level of melting and recrystallization starting at low temperatures for a quenched sample. The DSC data provided the total extent of melting, and this was contrasted with the drop in SAXS and WAXD intensities. SAXS and TMDSC temperature scans on a quenched, but still highly crystalline, POM sample were compared with the data from a high-temperature (145°C) isothermally crystallized POM sample with a higher degree of crystal perfection.

Tetrameric Assembly of Full-Sequence Protein Zero Myelin Glycoprotein by Synchrotron X-Ray Scattering

Highly purified myelin P0 glycoprotein was solubilized to 1–8 mg/ml in 0.1% sodium dodecyl sulfate (SDS), and the solution structure of the P0 assembly was studied using synchrotron x-ray scattering. The full-length P0, which was isolated from bovine intradural roots, included both the extracellular and cytoplasmic domains of the molecule. At the higher concentrations (4, 6, and 8 mg/ml, respectively), an x-ray intensity maximum was observed at 316 Å, 245 Å, and 240 Å Bragg spacing. Because the position of this intensity depended on P0 concentration, it is most likely due to interparticle interference. By contrast, the position of a second intensity maximum, which was at ∼40 Å Bragg spacing, was invariant with P0 concentration. This latter intensity was accounted for by monodispersed, 80 Å-diameter particles that are composed of eight, ∼30 Å-diameter spheres. Chemical parameters suggest that the 80 Å particles correspond to the size of a tetramer of P0 molecules. Therefore, the ∼30 Å spheres would correspond to the sizes of the extracellular and cytoplasmic domains for each of the P0 monomers. The invariance of the second intensity maximum with P0 concentration indicates that the structure of the 80 Å-diameter, tetrameric particles is unaltered. According to the liquid model for interparticle interference from charged spheres, the 80 Å-diameter particle has 10 negative surface charges which likely arise from negatively charged SDS molecules bound to the transmembrane domain of P0. This binding, however, apparently does not alter the tetrameric assembly of P0, suggesting that intermolecular interactions involving extracellular domains and cytoplasmic domains likely stabilize this assembly. Some of our results have been published in abstract form (Inouye, H., H. Tsuruta, D. A. Kirschner, J. Sedzik, and K. Uyemura. Abstracts of the 4th International School and Symposium on Synchrotron Radiation in Natural Science, June 15–20, 1998. Ustron-Jaszowiec, Poland. p. 31).

Studies of Structure and Morphology Development During the Heat-Draw Process of Nylon 66 Fiber by Synchrotron X-ray Diffraction and Scattering Techniques

Online studies of structure and morphology development during continuous drawing of a nylon 66 fiber at different temperatures were carried out using synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) techniques. From the two-dimensional (2D) WAXD measurement, unit-cell parameters were determined. The results confirm that the triclinic cell structure persists above the Brill transition temperature (about 443 K). With increasing temperature, the unit-cell dimension a (dominated by hydrogen bonding) remains almost unchanged, while b increases and c decreases (both show a step-change at 403 K, prior to the Brill transition). The constant value of a agrees with the argument that the hydrogen bonding is relatively immobile at high temperatures prior to melting. The step-changes in b and c suggest that a premelting process of small (or defective) crystals precedes the Brill transition. As a result, the anisotropic thermal expansion of the surviving larger crystals results in a step-change behavior. This hypothesis is consistent with the crystal density data as well as the morphology evaluation by SAXS. Several dimensions were extracted from the 2D SAXS data: lamellar crystal and amorphous thicknesses (along the fiber) determined by the correlation function method, and crystal fibril width (perpendicular to the fiber) determined by the Porod analysis. These results also indicate that drawing annihilates small crystals, but the strain effect is much less than the temperature effect.

Synchrotron X-ray Scattering Studies of Crystallization of Poly(ether-ether-ketone) from the Glass and Structural Changes during Subsequent Heating-Cooling Processes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynchrotron X-ray Scattering Studies of Crystallization of Poly(ether-ether-ketone) from the Glass and Structural Changes during Subsequent Heating-Cooling ProcessesAlain M. Jonas, Thomas P. Russell, and Do Y. YoonCite this: Macromolecules 1995, 28, 25, 8491–8503Publication Date (Print):December 1, 1995Publication History Published online1 May 2002Published inissue 1 December 1995https://doi.org/10.1021/ma00129a005RIGHTS & PERMISSIONSArticle Views450Altmetric-Citations104LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Small-angle synchrotron x-ray scattering reveals distinct shape changes of the myosin head during hydrolysis of ATP.

In the energy transduction of muscle contraction, it is important to know the nature and extent of conformational changes of the head portion of the myosin molecules. In the presence of magnesium adenosine triphosphate (MgATP), fairly large conformational changes of the myosin head [subfragment-1 (S1)] in solution were observed by small-angle x-ray scattering with the use of synchrotron radiation as an intense and stable x-ray source. The presence of MgATP reduced the radius of gyration of the molecule by about 3 angstrom units and the maximum chord length by about 10 angstroms, showing that the shape of S1 becomes more compact or round during hydrolysis of MgATP. Comparison with various nucleotide-bound S1 complexes that correspond to the known intermediate states during ATP hydrolysis indicates that the shape of S1 in a key intermediate state, S1-bound adenosine diphosphate (ADP) and phosphate [S1**.ADP.P(i)], differs significantly from the shape in the other intermediate states of the S1 adenosine triphosphatase cycle as well as that of nucleotide-free S1.

X-Ray Raman Spectrum of Li, Be and Graphite in a High-Resolution Inelastic Synchrotron X-Ray Scattering Experiment

The near edge fine structure of the X-ray Raman spectra in Li, Be and graphite was measured in an inelastic X-ray scattering experiment with 0.8 eV resolution. The X-ray Raman spectrum has been confirmed experimentally for q a <0.3 to be equivalent to the corresponding soft X-ray absorption spectrum, where \(\hbar q\) is the momentum transfer and a is the orbital radius of the inner-shell electrons. Anisotropic X-ray Raman spectra were observed for Be and graphite. Several experimental advantages of X-ray Raman scattering either over XUV-absorption experiment on low-Z elements or even over electron energy loss spectroscopy are stressed: true bulk information, admission of special environments, easy access to angular dependent information, small contributions of multiple scattering, higher-pole transitions for larger q , absolute scaling by means of sum rules.

Fluctuating Interfaces: a Series of Synchrotron X-Ray Scattering Studies of Interacting Stacked Membranes

AbstractIn this paper we concentrate on fluctuation phenomena encountered in interacting multilayered fluid membranes using synchrotron x-ray scattering as the primary tool. These systems consisting of surfactant or lipidic surfaces, are prototype models for understanding the statistical behavior of fluctuating surfaces embedded in three-dimensions. In elucidating the nature of fluid membranes we stress a unique intrinsic property: in contrast to usual surfaces with finite shear moduli, where surface tension plays a central role, the free energy of these essentially tensionless surfaces is governed by their geometrical shape and its fluctuations. We present data in a new regime of stability for very dilute and flexible membranes with interlayer separations of order hundreds of Angstroms. This is in contrast to most rigid membranes where the interlayer interactions are dominated by detailed microscopic interactions such as hydration and van der Waals. We show that the stability of these dilute lamellar phases is associated with violent out-of-plane fluctuations of the membranes giving rise to an effectively large long-range repulsive interaction theoretically elucidated by Helfrich. Because of its entropic origin, this interaction is universal and we present data for two different surfactant systems. Finally, we show that this new regime is distinct from the classical regime in which largely separated membrane sheets are stabilized because of their mutual electrostatic repulsion.

Synchrotron X-Ray Scattering for the Structural Characterization of Catalysts

Discussions exist in the literature concerning the application of single x-ray diffraction profile analysis to determine the average particle size, particle size distribution and root mean squared strain in catalytic systems. Nandi et al. have shown that the single order analysis can give erroneous strain results and is subject to error in the large particle size range. They further indicated that the initial slope of Stokes corrected Fourier coefficients gives more reliable average p article size than that which is calculated from single order peak shape analysis. There is apparent agreement that the average particle size and the particle size distribution measured by single order profile analysis, in small metal particle systems, are reliable.

Dynamic Structure Factor of Electrons in Li by Inelastic Synchrotron X-Ray Scattering

The dynamic structure factor, $S(\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}},\ensuremath{\omega})$, of single-crystal Li exhibits a strong anisotropy of peak position and peak dispersion. For $q&gt;{q}_{c}$ (${q}_{c}$ is the plasmon cutoff vector), at least the anisotropy of one peak position in $S(\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}},\ensuremath{\omega})$ can be attributed to zone-boundary collective states within the limits of a one-reciprocal-lattice-vector model. Therefore, the double-peak structure of $S(\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}},\ensuremath{\omega})$ for $q&gt;{q}_{c}$ seems not to be a universal property of the strongly correlated electron gas.