Polymers and fibers
SAXS can complement wide angle X-ray scattering (WAXS) X-ray diffraction measurements for a better understanding of the relationship of processing to material properties. The angular region examined in a SAXS experiment is typically from several hundredths of a degree to a few degrees 2θ. This small-angle region contains information about structures having large d-spacings (up to ~600 Å with pinhole optics).
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Figure 1: Small-angle scattering pattern of a polymer sheet cross-section showing a hexagonal columnar structure. This pattern can yield the arrangement of a column structure, its diameter, and the distances between columns. |
Small-angle X-ray scattering measurements can provide the following information:
- Lamellar repeat distance: The distance from the center of one bilayer to the center of its neighbor, which includes the thickness of associated water layers.
- Radius of gyration: The first moment of the scattering center distribution function.
- Particle size and shape: from Guinier's and Porod's Laws.
- Large-scale structure and long-range order: distances between similar structures.
This technique has been used extensively in polymer industries to characterize the morphological effects of drawing, rolling, and annealing on mechanical properties.
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Figure 2: Small-angle scattering pattern of a single polypropylene fiber. The fiber is oriented vertically. |
Samples for small-angle X-ray scattering include:
- Polymers and fibers (e.g. textile yarns)
- Wood products
- Detergents and surfactants
- Lipids and membranes
- Liquid crystals
- Glasses
- Catalysts