Shear-Induced Structural Evolution by SAXS/WAXS

Under shear, nanostructures undergo orientation, deformation, or phase reorganization. SAXS/WAXS detects these changes through the evolution of 2D scattering patterns as a function of shear rate.

From these measurements, SAXS/WAXS provides:

Orientation of nanodomains, derived from azimuthal intensity distributions
Degree of alignment, quantified through orientation factors or tensor-based analyses
Shear-induced phase transitions, indicated by the appearance, disappearance, or displacement of scattering peaks
Changes in characteristic length scales, such as domain spacing, correlation length, or aggregate dimensions
Coupled nanoscale and atomic-scale responses, when SAXS and WAXS are acquired simultaneously

Researchers can perform shear studies continuously (steady shear) or stepwise (oscillatory or transient shear) to directly correlate mechanical conditions with nanostructural evolution.

Figure 1. Quantitative analysis of shear-induced structural evolution in cellulose nanocrystals. Orientation factors extracted from radial and tangential SAXS geometries reveal three distinct regimes: an initial isotropic state at low shear rates, a strongly anisotropic alignment regime as shear increases, and a return toward isotropy at high shear due to flow-induced reorganization. The alignment trends mirror rheo-SAXS results, confirming the accuracy of laboratory-based shearSAXS in capturing flow-driven transitions.

SAXS/WAXS shear studies are applicable to a broad class of soft and complex materials, including: