Determining Full Sample Structure

This article describes how to establish the full structure of samples in SAXS/WAXS experiments without altering the sample-to-detector distance.

Prior to performing a new SAXS/WAXS experiment to determine the structure of an unknown sample, it is good practice to obtain data about its properties such that the study can focus on the q-ranges of interest. Obtaining this background information on a sample, from either the complementary methods or literature, can be tedious and is sometimes not possible.

The Discovery Mode with Pilatus3 R 1M combined with a SWAXS module can cover a large, continuous q-range from 0.037 to up to 30.53 nm-1. This unique ability allows researchers to identify relevant domains to do sample screening. The angular coverage is realized through a single measurement, which saves valuable time that is otherwise spent on detector motion along the beam axis.

Measurements and Results

A sample of block copolymer was studied with a SAXS/WAXS acquisition by using the Xeuss 2.0 SAXS/WAXS system. This experimental set-up integrates two types of DECTRIS detectors: a PILATUS3 R 1M detector and a proprietary hybrid pixel SWAXS module.

The SAXS sample-to-detector distance dSD SAXS is equivalent to 569 mm. A 10 minute exposure time was performed and the 2D patterns acquired are depicted in Figure 1.

2D SAXS and WAXS patterns

Figure 1. 2D SAXS (left - PILATUS3 R 1M detector) and WAXS (right - SWAXS module) patterns from a block copolymer sample obtained at dSD SAXS = 569 mm. Exposure time = 10 min. Axis unit = q [nm-1].

The matching scattering curve is shown in Figure 2, revealing the characteristic peaks in intensity across a large q-range (Table 1).

Scattering curve from a block copolymer sample

Figure 2. Scattering curve from a block copolymer sample resulting from simultaneous SAXS/WAXS measurement at dSD SAXS = 569 mm. Exposure time = 10 min.

Table 1. q-range and corresponding 2θ range. The Discovery Mode of the Xeuss 2.0 provides structural information about unknown samples nearly 3 decades in q (typical d_spacing [0.2 - 170] nm) with a single measurement.

q [nm-1] 2θ [°]
min 0.037 0.052
max 30.53 44.00

Such data allows simultaneous determination of a sample’s structures from the nanoscale to the crystalline scale. The scattered intensity covers over 5 magnitudes; emphasizing the capability to locate both strong and weak scattering signals.

If needed, a certain q-range of interest can be defined for further studies. A better angular resolution and flux/q-min compromise can be achieved if measurements are carried out at a longer sample-to-detector distance, while a larger azimuthal angle of detection can be realized if measurements are performed at a shorter detector distance.

To Go Further

The continuous extended data collection area of the Discovery Mode allows the exploration of a large number of samples. This high sampling volume considerably enhances the throughput of the Xeuss 2.0 SAXS/WAXS system.

To cite a few examples, the Discovery Mode also helps when comparing different types of processing conditions, exposing a completely disordered state or establishing structural organizations at different length scales.

Besides, on-site multi-scale dynamic analyzes and phase transitions studies can be carried out as a function of magnetic or electric fields, temperature and stretching forces.

Xenocs

This information has been sourced, reviewed and adapted from materials provided by Xenocs.

For more information on this source, please visit Xenocs.

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