Small Angle Neutron Scattering Research Papers (original) (raw)

This paper discusses the applicability of small angle X-ray scattering (SAXS) and small angle neutron scattering (SANS) techniques for determining the porosity, pore size distribution and internal specific surface area in coals. The method is noninvasive, fast, inexpensive and does not require complex sample preparation. It uses coal grains of about 0.8 mm size mounted in standard pellets as used for petrographic studies.

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- Geology, Small Angle X Ray Scattering, Sample Preparation, Coal Geology

ing neutral salt and a medium chain alcohol . There-The effect of medium chain alcohol molecules on the size and fore, these elements make the basic components in most shape of sodium dodecylsulfate micelles, and on the self-diffusion microemulsions. However, the intricate behavior of these coefficient of the surfactant and alcohol, has been investigated by mixed micellar aggregates makes it difficult to predict any means of small angle neutron scattering (SANS), and Fourier variation in the system upon variation in the composition of transform pulsed field gradient spin echo (FT-PGSE) nuclear the solution. This problem is caused by a delicate balance magnetic resonance measurements. All measurements were done of attractive and repulsive forces among the amphiphilic in D 2 O containing a sodium chloride concentration of 0.4 mol/kg, molecules in the micelles. and a surfactant concentration of 0.04 mol/kg. The alcohols used

- by Kell Mortensen
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- Engineering, Nuclear Magnetic Resonance, Physical sciences, Structural Change

The solution behavior of pectin polysaccharides has been investigated by small angle neutron scattering (SANS), viscosimetric, and molecular modeling studies. The samples used in the experimental study were obtainedfrom apple and citrus and had degrees of methylation ranging from 28 to 73%, with a rhamnose content lying between 0. and 2.2%. Persistence lengths, derived from intrinsic viscosity measurements, rangedfvom 59 to 126 A', whereas those derived by SANS were between 45 and 75 A'. These values correspond to 10-1 7 monomer units. The modeling simulations were performed for both homogalacturonan itselfand homogalacturonan carrying various degrees of rhamnose inserts (rhamnogulucturonun) . This required the evuluation of the accessible conformational space for lhe eight disaccharides that represent the constit-~ 339 340 Cros et a1 uent repealing segments of the homogalacturonan and rhamnogalacturonan pol.ysuccharides. For each dimer, complete conformational analysis was accvmplished using theflexible residue method ofthe MM3 molecular mechanics procedure and the results used to access the conjigurational stutistics of representative pectic polysaccharide chains. For homogalacturonan, an extended chain confirmation having a persistence length of 135 A' (corresponding to 30 monomers) was predicted. The inclusion of varying amounts of rhamnose units (5-25%) in the model in strict alternating sequence with galacturonate residues (equivalent to the rhamnogalacturonan "hairy region" chains) only slightly reduced the calculated persistence length. The extended overall chain conformation remained relativelv unchanged as a consequence ofthe self-cancellation of the kinking dfects of.siiccr.ssivepaired rhamnose units. 0 I996 John Wikv & Sons, Inc.

- by Serge Perez
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- Molecular modeling, Biological Sciences, Biopolymers, Viscosity

Small-angle neutron scattering (SANS) was used to investigate the interparticle interactions in concentrated dispersions of colloidal silica stabilized either by steric or by electrostatic repulsive interactions. In 10 mM NaCl, an adsorbed PEO layer is required to prevent flocculation, and particles are stabilized by steric repulsions. The adsorbed layer was made invisible to neutrons by contrast matching with the aqueous continuous phase. Dispersions of the same particles at the same concentrations but in the absence of added salt and adsorbed PEO were also studied. In both cases, the SANS spectra of concentrated dispersions show a peak at low Q, which is due to interparticle interactions: a structure factor. The SANS data can be described rather well by a homogeneous spherical form factor and a structure factor based on the Hayter-Penfold/Yukawa potential model. The steric potential was compared to the electrostatic potential obtained by fitting the SANS data of the bare silica dispersions. The steric potential shows a greater dependence on the particle volume fraction, which we ascribe to the penetration and compression of the adsorbed PEO layer as the particles approach.

- by Terence Cosgrove
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- Multidisciplinary, Langmuir, Small Angle Neutron Scattering

Laponite dispersions in water, at moderate ionic strength and high pH, are thixotropic: depending on previous history, they can be fluids or gels. The mechanisms of the fluid-gel and gel-fluid transitions have been examined through ionic analysis of the aqueous phase, static light, and small-angle neutron scattering, rheological experiments, and centrifugation. The results indicate that the particles attract each other in edge-to-face configurations. These attractions cause the particles to gather in microdomains, which subsequently associate to form very large fractal superaggregates, containing all the particles in the dispersion. A gel state is obtained when the network of connections is macroscopic. This network is destroyed by the application of sufficient strain, but it heals at rest. The addition of peptizers weakens the edge-to-face attractions, and makes the healing times much slower.

- by Frédéric Pignon and +2
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- Engineering, Mathematical Sciences, Physical sciences, Ionic Strength

The synthesis of semiconducting nanocrystals of manganese oxide of controlled sizes and their manipulation to form ordered arrays is described. Nanocrystalline mixed-valent manganese oxides have been prepared as colloidal solutions via reduction of tetraalkylammonium (methyl, ethyl, propyl, and butyl) permanganate salts in aqueous solutions with 2-butanol and ethanol. Reduction with the poorly water miscible 2-butanol produces aqueous colloids for the

- by Stephanie Brock
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- Engineering, Self Assembly, Quantum Confinement, Thin Film

A combination of ultra small angle X-ray scattering (USAXS) and ultra small angle neutron scattering (USANS) is used to characterize porous materials. The analysis methods yield quantitative information, including the mean skeletal chord length, mean pore chord length, skeletal density, and composition. A mixed cellulose ester (MCE) membrane with a manufacturer-labeled pore size of 0.1 m was used as a model to elucidate the specifics of the method. Four approaches describing four specific scenarios (different known parameters and form of the scattering data) are compared. Pore chords determined using all four approaches are in good agreement with the scanning electron microscopy estimates but are larger than the manufacturer's nominal pore size. Our approach also gives the average chord of the skeletal solid (struts) of the membrane, which is also consistent for all four approaches. Combined data from USAXS and USANS gives the skeletal density and the strut composition.

- by Neha Borkar and +1
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- Engineering, Membrane Science, Scanning Electron Microscopy, X Rays

The dispersion of alumina-coated TiO 2 particles by adsorption of the sodium salt of poly(acrylic) acid (PANa) was investigated in regard to the effective charge number of the particles. The effective surface charge number of the particles as well as the electrokinetic mobility only slightly increase with adsorption of PANa. Osmotic stress experiments have shown that PANa (MW 20 000) loses almost all of its effective charge once adsorbed. Moreover, small angle neutron scattering (SANS) experiments on suspensions at various volume fractions have shown that the structural arrangement of the particles is different in presence of adsorbed PANa only at very short distance (high volume fraction). These experimental evidences lead to the conclusion that the decrease of both the apparent viscosity and initial yield stress after adsorption of PANa can mostly be explained by a steric stabilization. The polyelectrolyte on the surface would prevent the weak but still undesirable aggregation of the particles when they collide. : S 0 9 2 7 -7 7 5 7 ( 0 0 ) 0 0 7 0 5 -6

- by Jacques Persello
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- Engineering, Physical sciences, Titanium dioxide, CHEMICAL SCIENCES

Latex film formation, the process by which an aqueous dispersion of polymer particles is transformed into a continuous material, has a direct bearing on the final film morphology and properties. Each of the primary stages of film formation (evaporative drying and ordering; particle deformation; and polymer interdiffusion) have been studied experimentally. Recently-developed non-invasive techniques, including direct nonradiative energy transfer, atomic force microscopy, small angle neutron scattering, environmental scanning electron microscopy, and various optical techniques have greatly enhanced the study of these stages. Even so, the exact cause (or causes) of particle deformation is still a topic of considerable debate. Several factors are experimentally known to influence latex film formation: the ambient conditions; the presence of surfactants, plasticizers and pigments; and latex particle structure. An important aim in the study of latex film formation is to understand the mechanisms by which these and other factors affect the process. New challenges lie in the study of film formation of core-shell latices, latex blends and new compositions. © 1997 Elsevier Science S.A.

- by Joseph Keddie
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- Engineering, Atomic Force Microscopy, Diffusion, Drying

15 16 Scattering methods offer the unique potential to indirectly probe materials on length 17 scales between the capabilities of modern crystallography and microscopy, thus 18 bridging the gap in spatial resolution between the two groups of techniques. The most 19 significant achievement of small-angle scattering techniques in starch science has 20 been the quantification of the lamellar architecture of semicrystalline growth rings in 21 native starch granules. The lamellae are structurally formed by side chains of 22 -2 -structural morphologies. This paper summarises previous investigations and the 35 current status of research into the structure of native starch and starch-based systems 36 using small-angle scattering techniques. 37 38

The influence of cholesterol on the structure of unilamellar-vesicle (ULV) phospholipid bilayers is studied using small-angle neutron scattering. ULVs made up of short-, mid-and long-chain monounsaturated phospholipids (diCn:1PC, n = 14, 18, 22, respectively) are examined over a range (0-45 mol %) of cholesterol concentrations. Cholesterol's effect on bilayer structure is characterized through changes to the lipid's transmembrane thickness, lateral area and headgroup hydration. For all three lipids, analysis of the experimental data shows that the addition of cholesterol results in a monotonic increase of these parameters. In the case of the short-and mid-chain lipids, this is an expected result, however, such a finding was unexpected for the long-chain lipid. This implies that cholesterol has a pronounced effect on the lipid's hydrocarbon chain organization.

- by Norbert Kučerka
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- Computer Simulation, Lipid Membranes, Mathematical Sciences, Cholesterol

Gravity distorts the circular contours found for small-angle neutron scattering data from azimuthally symmetric scattering systems when taken at long wavelength and with large wavelength spreads. The resolution is calculated for a... more

- by Robert Cubitt
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- Engineering, Physics, Gravity, Mathematical Sciences

New model of separated form factors is proposed for the evaluation of small-angle neutron scattering curves from large unilamellar vesicles. The validity of the model was checked by comparison to the model of hollow sphere. The model of separated form factors and hollow sphere model give reasonable agreement in the evaluation of vesicle parameters.

A geometrical Ewald construction for small-angle neutron scattering experiments from line-like objects with a preferential orientation of the lines, such as flux-line lattices in type-II superconductors, is described. The Ewald construction offers a straightforward way to interpret rocking-curve experiments. It allows calculation of the resolution function in rocking-curve measurements. The resolution function for a given instrumental geometry can be readily computed by performing two numerical integrations.

- by Ivo Dimitrov
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- Engineering, Mathematical Sciences, Physical sciences, Applied Crystallography

Thermal ageing of Cu-alloyed steels is a result of Cu-precipitates which arise above 300°C. Recently small angle neutron scattering was applied in order to analyse these precipitates in a defined initial state as well as in a thermally aged state. Atomistic computer simulations of the formation of precipitates can contribute to a deeper understanding of the mechanical behaviour of Cu-alloyed steels. A model is presented which is able to simulate the 'diffusion' of atoms by vacancy jumps . The underlying Monte Carlo method is presented and a binary system with components A and B is considered. Starting with a random distribution of atoms, the formation and growth of precipitates is simulated at a constant temperature of 600°C. In a second simulation, an initial temperature of 700°C is lowered to 400°C. At 700°C precipitates of radii between 1.1 and 1.7 nm are formed within seconds. At 400°C a part of the still dissolved atoms forms smaller precipitates while other atoms increase the size of the larger precipitates. At longer simulation times a significant decrease of the number of small precipitates and an increase of the averaged precipitate radius is found. The Russel-Brown theory is applied on the simulation results in order to calculate the increase of the yield stress in the thermally aged state. Ó

The structure of C 60 fullerene aqueous solution in dependence on the C 60 fullerene concentration in the water was studied and analyzed in detail using various spectroscopic techniques such as UV-VIS, Raman and IR-spectroscopy and small-angle neutron scattering (SANS). The obtained experimental results were confirmed by theoretical quantum-chemical calculations of the C 60 fullerene structure in water.

- by Peter Scharff
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- Engineering, Carbon, Physical sciences, CHEMICAL SCIENCES

A series of eight thermoplastic polyurethane elastomers were synthesized from 4,4-methylene diphenyl diisocyanate (MDI) and 1,4-butanediol (BDO) chain extender, with poly(hexamethylene oxide) (PHMO) macrodiol soft segments. The PHMO molecular weights employed ranged from 433 g/mol to 1180 g/mol. All materials contained 60% (w/w) of the macrodiol. The materials were characterized by differential scanning calorimetry (DSC) following up to nine different thermal treatments. In addition, three of the materials were selected for characterization by small-angle x-ray scattering (SAXS) following similar thermal treatments. The DSC experiments showed the existence of five hard segment melting regions (labelled T1-T5), which were postulated to result from the disordering or melting of sequences containing one to five MDIderived units, respectively. Evidence for urethane linkage dissociation and reassociation during annealing at temperatures above 150ЊC is presented. This process aids in the formation of higher melting structures. Annealing temperatures of 80-100ЊC provided the maximum SAXS scattering intensity values. Materials containing longer soft segments (and, therefore, longer hard segments) were observed to develop and sustain higher melting hard domain structures and also develop maximum average interdomain spacing values at higher annealing temperatures. Another additional series of three PHMO-based polyurethanes having narrower hard segment length distributions, was synthesized and characterized by DSC in the as-synthesized and annealed states. The resulting DSC endotherms provided further evidence to suggest that the T1-T5 endotherms were possibly due to melting of various hard segment length populations.

- by Simon J McCarthy
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- Engineering, Polymer science, Morphology, Nanoparticles

The elastic and tensile behavior of high-density, high-purity nanocrystalline Cu and Pd was determined. Samples with grain sizes of 10-l 10 nm and densities of greater than 98% of theoretical were produced by inert-gas condensation and warm compaction. Small decrements from coarse-grained values observed in the Young's modulus are caused primarily by the slight amount of porosity in the samples. The yield strength of nanocrystalline Cu and Pd was 10-15 times that of the annealed, coarse-grained metal. Total elongations of 14% were observed in samples with grain sizes less than 50 nm, while a sample with a grain size of 110 nm exhibited > 8% elongation, perhaps signifying a change in deformation mechanism with grain size. Hardness measurements followed the predictions of the Hall-Petch relationship for the coarse-grained copper down to x 15 nm, and then plateaued. Hardness values (divided by 3) were 2-3 times greater than the tensile yield strengths. Processing flaws may cause premature tensile failure and lower yield strengths. The size and distribution of processing flaws was determined by small-angle neutron scattering. Tensile strength increased with decreasing porosity, and may be significantly affected by a few large processing flaws. VI 1997 Acta Metallurgica Inc.

- by Jeffrey Eastman
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- Materials Engineering, Mechanical Engineering, Density, Elasticity

Small angle scattering of polarised neutron (SANSPOL) is a powerful technique for the determination of magnetisation, density and compositional profiles of nanostructured particles. We present here some examples of the magnetic profile determination using the SANSPOL technique and we discuss in detail its advantage with respect to the conventional small angle neutron scattering approach. r

The magnetic ordering of a single crystal of the cubic polymorph of FeGe has been studied by small-angle neutron scattering. The compound orders magnetically at TN = 278.7 K into a long-range spiral (period -683-700 A) propagating along equivalent directions at high temperatures and along equivalent (111) directions at low temperatures. The length of the spiral wavevector is nearly independent of temperature. The transition at TN is first order with very little hysteresis. The transition at which the direction of the spiral turns is rather sluggish. It takes place in a temperature interval of -40 K and shows pronounced temperature hysteresis ( T , = 211 K, T2 + = 245 K). Applied magnetic fields of 20-40 mT, depending on the temperature and the field direction, cause the spiral axis to turn into the direction of the applied field. As the field is further increased, the amplitude of the antiferromagnetic spiral decreases and the ferromagnetic component increases until at fields above -200-300 mT cubic FeGe becomes magnetically saturated. The magnetic ordering in cubic FeGe is a Dzyaloshinskii spiral similar to the structure observed in the isostructural compound MnSi. However, in MnSi the spiral propagates along equivalent (111) directions at all temperatures below TN = 29.5 K.

- by Jonte Bernhard
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- Materials Engineering, Condensed Matter Physics, Polymorphism, Nanotechnology

This paper examines the application of the statistical mechanics to the analysis of various physical properties of the elastomeric networks. The equilibrium properties of rubber-like networks are discussed, and also some dynamic properties, such as the relaxation spectrum of Gaussian networks. The paper covers a large spectrum of properties of polymer networks such as:¯uctuations and chain dimensions in unimodal and bimodal network, effects of entanglements and constraints on the elastic properties of the network, segmental orientation, liquid-crystalline networks, small angle neutron scattering from networks, strain birefringence, elastic properties of ®lled networks, strain induced crystallization etc. The paper shows that the statistical mechanics can be successfully used to the analysis of almost all physical properties of rubber-like networks. q

- by Andrzej Kloczkowski
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- Engineering, Statistical Mechanics, Polymer, CHEMICAL SCIENCES

In this article we report the physicochemical characterization of cationic liposomes loaded with orthocarborane and two of its sugar-containing derivatives. Carboranes are efficient boron delivery agents in boron neutron capture therapy, an anti-cancer treatment based on neutron absorption by 10B nuclei. Cationic liposomes were prepared using the positively charged DOTAP and the zwitterionic DOPE, as a helper lipid. These liposomes are currently used in gene therapy for their ability in targeting the cell nucleus; therefore they can be considered appropriate vectors for boron neutron capture therapy, in the quest of reducing the high boron amount that is necessary for successful cancer treatment. Boron uptake was determined by an original in situ method, based on neutron absorption. The structural properties of the loaded liposomes were studied in detail by the combined use of small angle x-ray scattering and small angle neutron scattering. These techniques established the global shape and size of liposomes and their bilayer composition. The results were discussed in term of molecular properties of the hosted drugs. Differences found in the insertion modality were correlated with the preparation procedure or with the specific shape and lipophilic-hydrophilic balance of each carborane.

- by Isabelle Grillo and +1
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- Gene Therapy, Small Angle X Ray Scattering, Biophysical Chemistry, Cancer treatment

Modified 9Cr-1Mo ferritic steel (T91/P91) has been subjected to a series of heat treatments consisting of soaking for 5 minutes at the selected temperatures, starting from the α-phase region (1073 K) to the γ + δ-phase region (1623 K), followed by oil quenching. Hardness measurements, microstructural features, and grain-size measurements by the linear-intercept method have been used for correlating them with the ultrasonic parameters. Ultrasonic velocity and attenuation measurements, and spectral analysis of the first backwall echo have been used for characterization of the microstructures obtained by various heat treatments. As the soaking temperature increased above Ac 1, the ultrasonic velocity decreased because of the increase in the volume fraction of martensite in the structure. There were sharp changes in the ultrasonic velocities corresponding to the two critical temperatures, Ac 1 and Ac 3. Ultrasonic longitudinal- and shear-wave velocities were found to be useful in identifying the Ac 1 and Ac 3 temperatures and for the determination of hardness in the intercritical region. However, ultrasonic attenuation and spectral analysis of the first backwall echo were found to be useful to characterize the variation in the prior-austenitic grain size and formation of δ ferrite above the Ac 4 temperature. The scattering coefficients have been experimentally determined for various microstructures and compared with the theoretically calculated value of the scattering coefficients for iron reported in literature.

Mixtures of a hydrophobic triblock copolymer (L121, PEO 5 PPO 68 PEO 5 ) and a hydrophobic anionic surfactant (AOT, Sodium bis(2-ethylhexyl)sulfosuccinate), each alone forming turbid vesicular solutions in water, aggregate to produce a thermodynamically stable, transparent and isotropic solution. Mixed AOT/L121 aggregates could be confirmed by fluorescence, surface tension, differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC). In an isotropic region, where mixed aggregates are formed, there is a synergistic interaction between monomers of AOT and L121 in the mixture. In addition, Small Angle Neutron Scattering (SANS) experiments provided evidence that mixed aggregates have the shape of either spheres (with a certain polydispersity) or very short ellipsoids (axial ratio below 2), confirming a transition from giant multilamellar vesicles to small aggregates upon mixing the two hydrophobic amphiphiles. Upon dilution, the morphology changes to disk-like. From an examination of the results of all the methods the peculiar behavior of the mixed AOT/L121 system is explained.

- by Rekha Shrestha
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- Materials Engineering, Thermodynamics, Block Copolymer, Micelles

We present experimental and theoretical results on the electrorheological response and microstructure of colloidal suspensions composed of silica nanoparticles dispersed in a silicon oil, as a function of electric field strength and silica water content. Using small-angle neutrons scattering experiments, we determined the evolution of the static structure factor of the suspensions when an electric field is applied. Experimental data were fitted with model calculations using the Percus-Yevick solution for Baxter's hard-sphere adhesive potential. The obtained stickiness parameter is directly related to the polarization interactions that depend on the water content of silica particles. The influence of the polarization interparticle potential on the rheology of the silica dispersions was investigated in a second time. A microscopic theory for the shear viscosity of adhesive hard-sphere suspensions was successfully used which describes the steady shear viscosity of suspension in terms of the fractal concept.  2004 Elsevier Inc. All rights reserved.

- by Jacques Persello
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- Engineering, Silica, Physical sciences, CHEMICAL SCIENCES

The aqueous solutions of sodium cumene sulphonate (NaCS) and its mixtures with each of cetyl trimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS) are characterized by small angle neutron scattering (SANS). NaCS when added to CTAB solution leads to the formation of long rod-shaped micelles with a dramatic increase in the CTAB aggregation number. Its addition to SDS on the other hand results in the formation of smaller mixed micelles where part of SDS molecules in the micelle is replaced by NaCS molecules.

- by Vilas Gaikar
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- Nuclear Magnetic Resonance, FTIR spectroscopy, NMR Spectroscopy, Chemical Shift

The aqueous solutions of sodium cumene sulfonate (NaCS) and its mixtures with cetyl trimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) are studied by Small Angle Neutron Scattering (SANS), Fourier Transform Infrared (FTIR) spectroscopy and Nuclear Magnetic Resonance (NMR) spectroscopy. The compositions of mixed micelles are determined using Rubingh's Regular Solution Theory. NaCS when added to CTAB solution leads to the formation of long rod shaped micelles with dramatic increase in the CTAB aggregation number. Its addition to SDS on the other hand results in the formation of smaller mixed micelles where parts of SDS molecules in the micelle are replaced by NaCS molecules. NaCS-SDS mixed micelles prefer elongated ellipsoidal geometry in order to accommodate short NaCS molecules. The FTIR spectroscopy results indicate enhanced ordering of CTAB tails inside the NaCS-CTAB mixed micelles with reduction in the gauche/trans conformer ratio. Addition of NaCS to SDS on the other hand results in decreased ordering of SDS tails, as compared to SDS micelles alone. The chemical shifts observed in 1 H NMR spectra of NaCS-SDS and NaCS-CTAB mixture indicate that NaCS resides near the surface of the SDS micelle.

- by Vilas Gaikar
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- Nuclear Magnetic Resonance, FTIR spectroscopy, NMR Spectroscopy, Chemical Shift

Micelle/water partition coefficients for three dialkyl phthalate esters -dimethyl phthalate ester (DMP), diethyl phthalate ester (DEP) and dipropyl phthalate ester (DPP) were obtained by micellar liquid chromatography (MLC). Experiments were conducted over a temperature range which led to calculation of a Gibbs free energy, enthalpy and entropy of transfer for the phthalate esters. In addition, small angle neutron scattering (SANS) experiments were conducted with no substantial change observed in micelle size before and after phthalate ester incorporation.

- by Marina Gallarate
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- Thermodynamics, Analytical Chemistry, Gibbs Free Energy, Thermal

Measurements on small angle neutron scattering (SANS) instruments are typically characterized by a large number of samples, short measurement times for the individual samples, and a frequent change of visiting scientist groups. Besides this, recent advances in instrumentation have led to more frequent measurements of kinetic sequences and a growing interest in analyzing two-dimensional scattering data, these requiring special software tools that enable the users to extract physically relevant information from the scattering data with a minimum of effort. The new 'BerSANS-PC' data-processing software has been developed at the Hahn-Meitner-Institut (HMI) in Berlin, Germany, to meet these requirements and to support an efficiently working guest-user service. Comprising some basic functions of the 'BerSANS' program available at the HMI and other institutes in the past, BerSANS-PC is a completely new development for network-independent use on local PCs with a full-feature graphical interface.

- by U. Keiderling
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- Condensed Matter Physics, Kinetics, Data Processing, Software Tool

Small-angle neutron scattering technique was used to study the effects of the microstructural change on the miscibility and the effective segmental interaction parameter (x) of deuterated polysulfone (d-PSU) and protonated PSU (PSU) blends. For the studies of the end-group effects on the miscibility and the x parameter, we prepared the three kinds of blends of d-PSU with PSU terminated with mostly Cl endgroup (PSU-Cl), PSU terminated with mostly OH end-group (PSU-OH) and PSU terminated with phthalic anhydride group (PSU-PhAh). For the studies of copolymerization effects, we prepared a copolymer of a sulfone unit and a monomer unit with COOH group (DPA unit) (PSU-COOH). The x parameters were estimated from the SANS profiles as a function of temperature for the blends of d-PSU with various modified PSUs and summarized in a figure in the text. Further, in the blends of d-PSU and PSU-PhAh, the x parameter was found to be very sensitive to the molecular weight of PSU-PhAh: if the molecular weight of PSU-PhAh is small, the blend was shown to be phase-separated, i.e. the effect of the end-group of PhAh on the miscibility and the x parameter was found to be very large. In the blend of d-PSU and PSU-COOH, the phase behavior was found to strongly depend upon the content of DPA unit included in PSU-COOH. The larger the content of DPA unit, the larger the x parameter. If the content was larger than a critical value, the blend was found to phase-separate. ᭧

- by Takeji Hashimoto
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- Engineering, Polymer, CHEMICAL SCIENCES, Phase Separation

The g9-g0 co-precipitates have a g9 particle at the core covered with a mantel of g0. When all six faces of a cubic g9 particle are coated with a shell of g0, this morphology is referred to as compact; however, when a disc-shaped g9... more

Basic principles and applications of different scattering techniques (including static and dynamic light scattering (SLS and DLS), small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD) and small-angle neutron scattering (SANS)) on the characterization of nanoparticles are reviewed in this paper. By choosing a suitable scattering technique or a combination of different techniques for nanoparticle characterization, the particles' molecular weight, radius of gyration, hydrodynamic radius, size distribution, shape and internal structure as well as interparticle interactions of nanoparticles, can be determined. Examples, including some sophisticated colloidal systems, are presented.

- by Tianbo Liu
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- Materials Engineering, Light Scattering, Nanoparticle, Small Angle X Ray Scattering

Building on previous work that considered spherical scatterers and randomly oriented spheroidal scatterers, we describe a multiple small-angle neutron scattering (MSANS) analysis for nonrandomly oriented spheroids. We illustrate this with... more

Evolution of magnetic excitations from purely magnetostatic modes to dipole-exchange spin waves in the Damon-Eshbach geometry in nanocomposite ͑SiO 2 ͒ 100−x Co x ͑50 at. % Ͻ x Ͻ 80 at. %͒ films during a transition from superparamagnetic to superferromagnetic state has been studied by Brillouin light scattering. It has been shown that removal of the degeneracy of backward volume magnetostatic waves due to nonzero exchange constant manifests itself in more pronounced Stokes/ anti-Stokes asymmetry. Accompanying static characterization by means of magnetic force microscopy imaging and grazing incidence small angle neutron scattering has demonstrated the presence of weak stripe domains in the superferromagnetic phase.

- by Vladimir Belotelov
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- Engineering, Light Scattering, Applied Physics, Magnetic Force Microscopy

of the original manuscript: Zavisova, V.; Koneracka, M.; Muckova, M.; Lazova, J.; Jurikova, A.; Lancz, G.; Tomasovicova, N.; Timko, M.; Kovac, J.; Vavra, I.; Fabian, M.; Feoktystov, A.V.; Haramus, V.M.; Avdeev, M.V.; Kopcansky, P.:

We have carried out several measurements in order to understand the process of metal nanoparticle (MNP) film sintering. Small angle neutron scattering has been used to reveal the average diameters of silver and gold nanoparticles (Ag-NPs and Au-NPs) used in this study to be 4.6 and 3.8 nm, respectively, with a size distribution of ca. 20%. Spuncast Ag-NP and Au-NP films have been sintered at temperature ranges of 80 -160°C and 180 -210°C, respectively, for various times.

Electrostatic interactions between synthetic polyelectrolytes and proteins can lead to the formation of dense, macroion-rich liquid phases, with equilibrium microheterogeneities on length scales up to hundreds of nanometers. The effects of pH and ionic strength on the rheological and optical properties of these coacervates indicate microstructures sensitive to protein-polyelectrolyte interactions. We report here on the properties of coacervates obtained for bovine serum albumin (BSA) with the biopolyelectrolyte chitosan and find remarkable differences relative to coacervates obtained for BSA with poly(diallyldimethylammonium chloride) (PDADMAC). Coacervation with chitosan occurs more readily than with PDADMAC. Viscosities of coacervates obtained with chitosan are more than an order of magnitude larger and, unlike those with PDADMAC, show temperature and shear rate dependence. For the coacervates with chitosan, a fast relaxation time in dynamic light scattering, attributable to relatively unrestricted protein diffusion in both systems, is diminished in intensity by a factor of 3-4, and the consequent dominance by slow modes is accompanied by a more heterogeneous array of slow apparent diffusivities. In place of a small-angle neutron scattering Guinier region in the vicinity of 0.004 Å -1 , a 10-fold increase in scattering intensity is observed at lower q. Taken together, these results confirm the presence of dense domains on length scales of hundreds of nanometers to micrometers, which in coacervates prepared with chitosan are less solidlike, more interconnected, and occupy a larger volume fraction. The differences in properties are thus correlated with differences in mesophase structure.

- by Sabina Strand
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- Engineering, Rheology, Chitosan, Transmission Electron Microscopy

Herein, we present the first unambiguous evidence for hydrated reverse micelles (RMs) in dense or supercritical carbon dioxide (scCO2). These RMs are formed with a low cost designer triple hydrocarbon chain surfactant, sodium... more

Silk–elastinlike protein polymer, SELP-815K, with eight silk and fifteen elastin units and a lysine (K) modified elastin, was genetically engineered with longer silk and elastin units compared to existing hydrogel forming analogs (SELP-415K and SELP-47K). Hydrogels of the three SELPs (with similar MWs) were investigated for their structure–function relationships. Results indicate that equilibrium swelling ratio in these hydrogels is a function of polymer structure, concentration, cure time and ionic strength of media. Swelling was not influenced by the changes in pH. Storage moduli observed by dynamic mechanical analysis and the Debye–Bueche correlation length obtained from small-angle neutron scattering provided structural insight that suggests the cross-linking densities in these hydrogels follow the order SELP-47K > SELP-815K > SELP-415K. These results allude to the importance of the length of elastin blocks in governing the spacing of the cross-linked hydrogel network and that of silk in governing the stiffness of their 3-dimensional structures.

- by Von Cresce
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- Engineering, Hydrogels, Genetic Engineering, DNA

Therefore the entropy change of transition, from the compact to the extended coil form, of (MA-DSt), may be more negative than that of (MA-St), due to a more extensive hydration of (MA-DSt), in the coil form. Also, the transition enthalpy AH,' of (MA-DSt), can be expected to be somewhat larger than that of (MA-St),, because the increase in size of the phenyl residue on deuteration results in weak van der Waals interactions in the compact form. Thus the compact form of the deuterated polymer is suggested to be more stable than that of the nondeuterated one.

- by B. Crist
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- Engineering, Macromolecules, CHEMICAL SCIENCES, Small Angle Neutron Scattering

We measured the shape and the internal dynamics of starlike dendrimers under good solvent conditions with small-angle neutron scattering and neutron spin-echo ͑NSE͒ spectroscopy, respectively. Architectural parameters such as the spacer length and generation were varied in a systematic manner. Structural changes occurring in the dendrimers as a function of these parameters are discussed, i.e., in terms of the fractal dimension and deviations of the radius of gyration from the Gaussian value. A first cumulant evaluation of the NSE spectra for each scattering vector q separately yields the length scale dependent relaxation rates. We observe a local minimum in the normalized relaxation rates ⍀͑q͒ / q 3 on length scales corresponding to the overall dendrimer dimension. The dynamics is discussed within a Rouse-Zimm approach generalized to the case of starlike dendrimers of arbitrary geometry. The model allows an identification of the modes contributing to the relaxation of the dendrimer in the q and time range of the NSE experiment. The local minimum is due to collective breathing motions of ͑parts of͒ the dendrons relative to each other. Shape fluctuations are not observed.

- by Mikael Trollsas
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- Engineering, Chemical Physics, Physical sciences, Structural Change

The lamellar structure of a symmetric diblock copolymer was studied as a function of temperature. We used dPEP-PDMS with a molecular weight of 8.3 kgrmol as model system. The polymer was dissolved in chloroform and spin-casted on silicon wafers into thin uniform films. The degree and direction of lamellar ordering in the thin films was measured by small angle neutron scattering. Neutron reflectivity was used to measure the detailed lamellar structure in the thin films. For the temperature scans only the first order Bragg peak was measured to determine the lamellar period in the film. Our experimental results are compared to theoretical predictions on the scaling behavior of the lamella period as a function of temperature. The morphology of the surface was investigated by atomic force microscopy. Holes were found around defects in the films. The cross-section of the holes revealed the lamellar structure with a periodicity comparable to what was found by neutron reflectivity. q

- by Nikolaj Gadegaard
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- Atomic Force Microscopy, Multidisciplinary, Thin Films, Pl

When exposed for long time at elevated temperatures of 430 and 650 • C the nickel base superalloy EI 698 VD can experience a significant decrease in creep resistance. The cause of the creep degradation of nickel base superalloy is generally attributed to the microstructural instability at prolonged high temperature exposure. In this article, the creep-life data, generated on long thermally exposed nickel base superalloy EI698 VD were related to the local microstructural changes observed using SEM and TEM analysing techniques. While structure analysis provided supporting evidence concerning the changes associated with grain boundary carbide precipitation, no persuasive evidence of a morphological and/or dimensional gamma prime change was showed. For clarifying of the role of gamma prime precipitates on alloy on creep degradation, the SANS (small angle neutron scattering) experiment was crucial in the characterization of the bulk-averaged gamma prime morphology and its size distribution with respect to the period of thermal exposure.

- by Jozef Zrnik
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- Materials Engineering, Mechanical Engineering, Structure Analysis, High Temperature

We have studied by Small Angle Neutron Scattering the structure of beta-casein in aqueous solutions in a wide range of temperatures and denaturant concentrations. For higher temperatures and low denaturant concentrations, we find micelles. These may be described by using a two shell model with constant concentration in every shell. When either temperature is lowered or denaturant concentration is raised, the aggregation number of the micelles decreases, until it reaches unity at a critical temperature or a critical concentration. Beyond this threshold, single isolated casein molecules are present. For both cases, the results are interpreted in terms of synthetic polymers, by a copolymer model. We introduce an excluded volume parameter describing the hydrophobic sequences. We assume that it depends on both temperature and denaturant concentration, that varies and eventually changes sign as either of these parameters is varied. This leads to some power law variations that are in reasonable agreement with the experiments.

- by Mohamed Taoufik Daoud
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- Engineering, Micelle, Polymer, Power Law

We report on measurements of spatial beam modulation of a polarized neutron beam induced by triangular precession regions in time-of-flight mode and the application of this novel technique spin-echo modulated small-angle neutron scattering (SEMSANS) to small-angle neutron scattering in the very small angle range. It is shown that this method can be implemented straight-forwardly in order to extend the accessible size range of structures to be investigated by SANS towards a microscopic scale by applying a divergent beam and measuring the real space correlation function. The novel approach of SEMSANS enables the application of sophisticated sample environment and measurements of magnetic samples (in contrast to the analogue method SESANS). V C 2012 American Institute of Physics. [http://dx.

- by A. Tremsin
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- Engineering, Materials Engineering, Mechanical Engineering, Applied Physics

Small-angle neutron scattering (SANS) measurements are reported on a sterically stabilized, coreshell colloidal system using contrast variation. Aqueous dispersions of polystyrene particles bearing grafted poly(ethylene glycol) (PEG) have been studied over a large range of particle concentrations and two different solvent conditions for the PEG polymer. SANS data are analyzed quantitatively by modeling the particles as core-shell colloids. In a good solvent and under particle contrast conditions, an effective hard-sphere interaction captures excluded-volume interactions up to high concentrations. Contrast variation, through isotopic substitution of both the core and solvent, expedite a detailed study of the PEG layer, both in the dilute limit and as a function of the particle concentration. Upon diminishing the solvent quality, subtle changes in the PEG layer translate into attractions among particles of moderate magnitude.

We report Mossbauer source experiments on disordered ' CoPdsoCo2o, and ask if there is any evidence for weak ferromagnetic random anisotropy (RA) near the critical point. In making this search we are encouraged by the fact that Co has an unquenched orbital angular momentum, and that there is evidence of local-moment disalignment in small-angle neutron scattering. Spectra taken over the temperature range 89 & T & 507 K were well fitted by a continuous magnetic hyperfine field distribution which can be described by a modal field, Hhf(T), and a full width at half maximum (FWHM) bH"t(T). Hht(T) was used to deduce P=0.38(3) for the range 10 (1-T/Tc &2X10. Though insuSciently asymptotic for a strict test of theory, this value is in agreement with predictions for the random-exchange Heisenberg model. EHhf(T) is found to increase above 320 K, a behavior that can be described via a local-moment mean-field theory which assumes the "Fe Mossbauer site has a 17% FWHM distribution in the exchange constant and a 10% FWHM distribution in Hhf(0). Neither the deduced critical behavior nor the observed hyperfine-field broadening requires the attribution of RA effects. The only evidence of the possible presence of RA in our experiments is the fact that cold working substantially broadens both T& and the hyperfinefield distribution near T&.