scholarly journals A small-angle neutron scattering investigation of rigid polyelectrolytes under shear

2003 ◽  
Vol 36 (4) ◽  
pp. 1000-1005 ◽  
Author(s):  
E. Mendes ◽  
S. Viale ◽  
O. Santin ◽  
M. Heinrich ◽  
S. J. Picken
Keyword(s):  
Neutron Scattering ◽  
Cross Sections ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Deuterated Water ◽  
Shear Rates ◽  
Scattering Spectrum ◽  
High Shear Rates ◽  
Low Concentrations ◽  
Small Shear

Solutions of a rigid polyelectrolyte molecule, sulfo-poly(phenyleneterephthalamide) (SPTTA), in deuterated water have been investigated using small-angle neutron scattering. At low concentrations (1 wt%) the scattering spectrum presents a soft maximum similar to that of the interaction of rod-like objects. Two counterions are used, H+and Li+, and it is shown that aggregation is favoured as the proportion of Li+counterions increases. When kept at rest at room temperature, the solutions exhibit spontaneous birefringence. A 1 wt% solution was investigated under shear and it is shown that a very small shear rate is needed to produce a very strong alignment of rod-like objects. Such alignment saturates at high shear rates. Upon cessation of shear, a very long relaxation time is observed. The set of results strongly suggest aggregation of rigid polyelectrolyte molecules into long needles exhibiting very small cross sections.

Capillary RheoSANS: measuring the rheology and nanostructure of complex fluids at high shear rates

Soft Matter ◽  
2020 ◽  
Vol 16 (27) ◽  
pp. 6285-6293
Author(s):  
Ryan P. Murphy ◽  
Zachary W. Riedel ◽  
Marshall A. Nakatani ◽  
Paul F. Salipante ◽  
Javen S. Weston ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Complex Fluids ◽  
Inorganic Nanoparticles ◽  
High Shear ◽  
Capillary Rheometry ◽  
Shear Rates ◽  
High Shear Rates

Capillary rheometry is combined with small-angle neutron scattering to simultaneously measure the viscosity and nanostructure of complex fluids containing proteins, surfactants, polymers, and inorganic nanoparticles at shear rates up to 106 s−1.

Shear Induced Phase Behavior of Polymer Blends by Small Angle Neutron Scattering

1989 ◽  
Vol 166 ◽  
Author(s):  
Alan I. Nakatani ◽  
Hongdoo Kim ◽  
Charles C. Han
Keyword(s):  
Neutron Scattering ◽  
Polymer Blends ◽  
Phase Behavior ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Large Body ◽  
Concentric Cylinder ◽  
Shear Rates ◽  
Lower Shear ◽  
High Shear Rates

ABSTRACTThe phase behavior of polymer blends and solutions can be changed dramatically by a flow field using a variety of flow geometries. Unlike simple binary fluids which require extremely high shear rates to produce only small shifts in the phase boundary, polymer phase behavior may be influenced by as much as 10 degrees with the application of much lower shear rates. However, there is a large body of conflicting data concerning the nature of these shear effects in polymers.Here we report on the effects of shear on the phase behavior of polymer blends by small angle neutron scattering (SANS). Experiments were conducted using a specially constructed, concentric cylinder apparatus for in situ studies of concentrated polymer solutions and melts. Two separate systems will be discussed: 1) a blend of polystyrene and polybutadiene. 2) a blend of polystyrene and poly(vinylmethylether). Both systems exhibit shifts in the phase behavior which indicate shear induced mixing in agreement with previous results obtained by other techniques. These results will be interpreted within the context of existing theories of shear induced phase behavior.

Correction method for the asymmetry of the tangential beam in Couette (or Searle) geometry used in rheo-small-angle neutron scattering

2004 ◽  
Vol 37 (3) ◽  
pp. 438-444 ◽  
Author(s):  
Florian Nettesheim ◽  
Ulf Olsson ◽  
Peter Lindner ◽  
Walter Richtering
Keyword(s):  
Neutron Scattering ◽  
Cross Sections ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Correction Method ◽  
Shear Cell ◽  
The Asymmetry ◽  
The Difference ◽  
Scattering Cross Sections ◽  
Final Expression

A method of correcting the asymmetry in the scattering of the tangential beam configuration in a rheo-small-angle neutron scattering experiment is proposed. The asymmetry of the scattering in the tangential beam configuration can be attributed to the difference in pathlength for neutrons that are scattered toward compared with those which are scattered away from the axis of rotation of the shear cell. The pathlength problem is solved and a final expression for the two-dimensional scattering intensity is given. The results from these calculations are compared with experimental data, which offer a different option to correct this asymmetry, namely by just measuring the scattering of H2O/D2O mixtures with absolute scattering cross sections identical to those of the respective samples. However, the situation for anisotropic media is more complex and the correction procedure described here is less effective.

Small-angle neutron scattering study of shear-induced phase separation in aqueous poly(N-isopropylacrylamide) solutions

e-Polymers ◽  
2004 ◽  
Vol 4 (1) ◽  
Author(s):  
Markus Stieger ◽  
Peter Lindner ◽  
Walter Richtering
Keyword(s):  
Phase Separation ◽  
Shear Flow ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Separation Process ◽  
High Shear ◽  
Shear Rates ◽  
High Shear Rates ◽  
Strong Shear ◽  
Phase Separation Process

Abstract The influence of shear flow on the structure of concentrated aqueous poly(N-isopropylacrylamide) solutions near the lower critical solution temperature was investigated by means of small-angle neutron scattering. Two samples, both in the semi-dilute regime above the overlap concentration, were studied. The scattering curve of the less concentrated sample was not influenced by shear flow, although high shear rates were reached. The more concentrated 4 wt.-% sample, however, displayed shear-induced demixing under strong shear flow conditions. Experiments at different shear stresses indicated the existence of a threshold shear stress and the phase separation process became faster with increasing stress. The two-dimensional scattering patterns remained isotropic even during the phase separation process and the correlation length as obtained from an Ornstein- Zernike plot increased. The influence of shear flow on the phase separation process is thus similar to a temperature increase. The results are in excellent agreement with data from recent rheo-optical experiments where shear-induced phase separation was also observed for the concentrated solution at high shear rates. Apparently, strong shear flow exerts an effect analogous to a temperature increase.

Small-Angle Neutron Scattering from YBa2Cu3O7 and Bi2Sr2CaCu2O8 Near the Critical Temperature

1994 ◽  
Vol 376 ◽  
Author(s):  
C. D. Frost ◽  
G.L. Squires
Keyword(s):  
Critical Temperature ◽  
Sample Preparation ◽  
Neutron Scattering ◽  
Cross Sections ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Crystalline Defects ◽  
Scattering Potential ◽  
The Difference ◽  
Scattering Cross Sections

ABSTRACTOne of the 30 meter small-angle neutron scattering spectrometers at NIST has been used to measure the scattering from YBa2Cu3O7 and Bi2Sr2CaCu2O8 at a range of temperatures from 35 K to 135 K with wavevector transfers Q from 0.01 Å-1 to 0.08 Å-1. Considerable attention was paid to sample preparation in order to reduce the background scattering from crystalline defects and stoichiometric variations in the sample. For both materials, the difference in the differential scattering cross-sections at the critical temperature Tc and at temperatures of Tc ± 20 K showed considerable structure in Q, corresponding to spatial variations in the neutron scattering potential with Fourier components of wavelength of the order of 100 Å.

Absolute Calibration of Small-Angle Neutron Scattering Data of a Double-Crystal Diffractometer

1997 ◽  
Vol 30 (5) ◽  
pp. 857-861 ◽  
Author(s):  
F. Carsughi ◽  
D. Bellmann ◽  
J. Kulda ◽  
M. Magnani ◽  
M. Stefanon
Keyword(s):  
Neutron Scattering ◽  
Cross Section ◽  
Cross Sections ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Scattering Data ◽  
Absolute Calibration ◽  
Double Crystal ◽  
Similar Materials ◽  
Double Crystal Diffractometer

Small-angle neutron scattering (SANS) experiments generally provide the absolute SANS cross sections and this allows quantitative results to be obtained; however, data collected at double-crystal diffractometers are frequently not normalized to absolute cross sections and they are used only for qualitative analysis. In point-geometry diffractometers, the normalization is done by comparing the scattered intensities to those of samples of known cross sections or by measuring the direct-beam intensity; in the double-crystal diffractometer, the incident flux information is contained in the rocking curve measured without a sample and this feature can therefore be used to normalize the scattered intensities to the SANS cross sections. A sample of thickness 1 mm of the Ni-based superalloy UDIMET 520 was analyzed at a double-crystal diffractometer; the SANS cross section obtained by the proposed procedure compares well with the SANS cross section found for similar materials by using conventional point-geometry diffractometers and calibrated by light water.

scholarly journals Magnetic Small-Angle Neutron Scattering

2021 ◽  
Author(s):  
Andreas Michels
Keyword(s):  
Neutron Scattering ◽  
Cross Sections ◽  
Small Angle ◽  
Spin Glasses ◽  
Small Angle Neutron Scattering ◽  
Continuum Theory ◽  
Real Space ◽  
Theoretical Background ◽  
Magnetic Interactions ◽  
Comprehensive Treatment

This book provides the first extensive treatment of magnetic small-angle neutron scattering (SANS). The theoretical background required to compute magnetic SANS cross sections and correlation functions related to long-wavelength magnetization structures is laid out; and these concepts are scrutinized based on the discussion of experimental neutron data. Regarding prior background knowledge, some familiarity with the basic magnetic interactions and phenomena, as well as scattering theory, is desired. The target audience comprises Ph.D. students and researchers working in the field of magnetism and magnetic materials who wish to make efficient use of the magnetic SANS method. Besides revealing the origins of magnetic SANS (Chapter 1), and furnishing the basics of the magnetic SANS technique (Chapter 2), much of the book is devoted to a comprehensive treatment of the continuum theory of micromagnetics (Chapter 3), as it is relevant for the study of the elastic magnetic SANS cross section. Analytical expressions for the magnetization Fourier components allow one to highlight the essential features of magnetic SANS and to analyze experimental data both in reciprocal (Chapter 4) and real space (Chapter 6). Chapter 5 provides an overview of the magnetic SANS of nanoparticles and so-called complex systems (e.g., ferrofluids, magnetic steels, spin glasses, and amorphous magnets). It is this subfield where major progress is expected to be made in the coming years, mainly via the increased use of numerical micromagnetic simulations (Chapter 7), which is a very promising approach for the understanding of the magnetic SANS from systems exhibiting nanoscale spin inhomogeneity.

Small-Angle Neutron Scattering Study of Poly(oxyethylene)-block-poly(oxypropylene)-block-poly(oxyethylene) in Aqueous Solutions

1993 ◽  
Vol 58 (10) ◽  
pp. 2428-2436 ◽  
Author(s):  
Herman Pospíšil ◽  
Josef Pleštil ◽  
Zdeněk Tuzar
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Structural Parameters ◽  
Second Virial Coefficient ◽  
Scattering Data ◽  
Radius Of Gyration ◽  
Deuterated Water ◽  
Neutron Scattering Study ◽  
Copolymer Poly

Solutions of a triblock copolymer, poly(oxyethylene)-block-poly(oxypropylene)-block-poly(oxyethylene) (POE-POP-POE), in deuterated water were studied by small-angle neutron scattering (SANS) in the temperature range from 20 to 45 °C. Radius of gyration, molecular weight, second virial coefficient for both unimers and micelles, critical micelle concentration and unimer concentration were determined from the scattering data. Under assumption of the spherical core/shell micellar model structural parameters were estimated. Degree of swelling of the micellar core was evaluated from the mean-square fluctuation of scattering density.

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