Determining Full Sample Structure in SAXS/WAXS Experiments Without Changing the Sample to Detector Distance

Table of Contents

Introduction
Measurements and Results
To go further

Introduction

This article shows how to determine the full structure of samples in SAXS/WAXS experiments without modifying the sample-to-detector distance.

When a new SAXS/WAXS experiment is being considered to determine the structure of an unknown sample, it is good practice to get prior data about its properties in order to focus the study on the q-ranges of interest. Getting this background information on a sample, from either the literature or complementary methods, can be tedious and is not always possible.

The Discovery Mode with Pilatus3 R 1M and a SWAXS module is capable of covering a large, continuous q_range from 0.037 to up to 30.53 nm-1. This unique capability allows and enables researchers to identify relevant domains to perform sample screening. As the angular coverage is realized through a single measurement there is also no need to spend valuable time on detector motion along the beam axis.

Measurements and Results

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

The SAXS sample-to-detector distance dSD SAXS is equivalent to 569 mm. An exposure time of 10 minutes was carried out and the 2D patterns acquired are shown in Figure 1.

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

Figure 2 shows the matching scattering curve, which reveals characteristic peaks in intensity across a large q_range (Table 1).

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

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 enable to determine the structures of a sample from the nanoscale to the crystalline scale at the same time. The scattered intensity covers over 5 magnitudes; highlighting the capability to locate strong as well as weak scattering signals.

If required, a certain q_range of interest can be defined for additional studies. A better angular resolution as well as flux/q_min compromise can be realized if measurements are performed at a longer sample-to-detector distance, while a larger azimuthal angle of detection can be realized if measurements are carried out at a shorter detector distance.

To go further

With its continuous extended data collection area,  the Discovery Mode enables the exploration of a large number of samples. This high sampling volume significantly improves the throughput of the Xeuss 2.0 SAXS/WAXS system.

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

In addition, on-site multi-scale dynamic analyses and phase transitions studies can be performed as a function of stretching forces, temperature, and magnetic or electric fields.

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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