Poiseuille and extensional flow small-angle scattering for developing structure–rheology relationships in soft matter systems

Small-angle scattering methods have become routine techniques for the structural characterization of macromolecules and macromolecular assemblies like polymers, (block) copolymers or micelles in the spatial range from a few to hundreds of nanometres. Neutrons are valuable scattering probes, because they offer freedom with respect to scattering length density contrast and isotopic labelling of samples. In order to gain maximum benefit from the allotted experiment time, the instrumental setup must be optimized in terms of statistics of scattered intensity, resolution and accessible range in momentum transferQ. The new small-angle neutron scattering instrument V16/VSANS at the Helmholtz-Zentrum in Berlin, Germany, augments neutron guide collimation and pinhole optics with time-of-flight data recording and flexible chopper configuration. Thus, the availableQrange and the respective instrumental resolution in the intermediate and high momentum transfer regions can be adjusted and balanced to the individual experimental requirements. This renders V16/VSANS a flexible and versatile instrument for soft-matter research.

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Small-angle scattering on soft matter with dynamical asymmetry

Journal of Applied Crystallography ◽

10.1107/s0021889803006216 ◽

2003 ◽

Vol 36 (3) ◽

pp. 381-388 ◽

Cited By ~ 3

Author(s):

Satoshi Koizumi

Keyword(s):

Small Angle ◽

Soft Matter ◽

Small Angle Scattering ◽

Angle Scattering

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Contrast matching of an Si substrate with polymer films by anomalous dispersion at the SiKabsorption edge

Journal of Applied Crystallography ◽

10.1107/s002188981105206x ◽

2011 ◽

Vol 45 (1) ◽

pp. 119-121 ◽

Cited By ~ 7

Author(s):

Hiroshi Okuda ◽

Kohki Takeshita ◽

Shojiro Ochiai ◽

Yoshinori Kitajima ◽

Shinichi Sakurai ◽

...

Keyword(s):

Small Angle ◽

Triblock Copolymer ◽

Soft Matter ◽

Grazing Incidence ◽

Small Angle Scattering ◽

Anomalous Dispersion ◽

Two Dimensional ◽

Si Substrate ◽

Angle Scattering ◽

Contrast Matching

Anomalous dispersion at the SiKabsorption edge has been used to control the reflection from the interface between a film and an Si substrate, which otherwise complicates the nanostructure analysis of such a film, particularly for the soft-matter case, in grazing-incidence small-angle scattering. Such a reflectionless condition has been chosen for a triblock copolymer thin film, and two-dimensional grazing-incidence small-angle scattering patterns were obtained without the effect of the reflection. The present approach is useful for analysing nanostructures without introducing complicated corrections arising from the reflection.

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Experimental noise in small-angle scattering can be assessed using the Bayesian indirect Fourier transformation

Journal of Applied Crystallography ◽

10.1107/s1600576721006877 ◽

2021 ◽

Vol 54 (5) ◽

pp. 1281-1289 ◽

Cited By ~ 2

Author(s):

Andreas Haahr Larsen ◽

Martin Cramer Pedersen

Keyword(s):

Small Angle ◽

Fourier Transformation ◽

Soft Matter ◽

Small Angle Scattering ◽

Scattering Data ◽

Data Set ◽

Angle Scattering ◽

Experimental Errors ◽

Multiple Data Sets ◽

Model Fits

Small-angle X-ray and neutron scattering are widely used to investigate soft matter and biophysical systems. The experimental errors are essential when assessing how well a hypothesized model fits the data. Likewise, they are important when weights are assigned to multiple data sets used to refine the same model. Therefore, it is problematic when experimental errors are over- or underestimated. A method is presented, using Bayesian indirect Fourier transformation for small-angle scattering data, to assess whether or not a given small-angle scattering data set has over- or underestimated experimental errors. The method is effective on both simulated and experimental data, and can be used to assess and rescale the errors accordingly. Even if the estimated experimental errors are appropriate, it is ambiguous whether or not a model fits sufficiently well, as the `true' reduced χ2 of the data is not necessarily unity. This is particularly relevant for approaches where overfitting is an inherent challenge, such as reweighting of a simulated molecular dynamics trajectory against small-angle scattering data or ab initio modelling. Using the outlined method, it is shown that one can determine what reduced χ2 to aim for when fitting a model against small-angle scattering data. The method is easily accessible via the web interface BayesApp.

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