Shear-induced macroscopic "Siamese" twins in soft colloidal crystals
Stephan Förster, Sara Schröder (Mehdizadeh Taheri), Sabine Rosenfeldt, S. Fischer, P. Bösecke, T. Narayanan, P. Lindner:
Soft Matter, 9, 8464-8475: Soft Matter (2013).
doi: 10.1039/c3sm51075a


Soft colloidal crystals are inherently highly susceptible to shear. We find by
using scanning rheo-SANS and scanning synchrotron-rheo-SAXS experiments
that high shear strains cause macroscopic Siamese twinning in lyotropic
FCC-crystals formed by block copolymer micelles or polymer-coated nanoparticles.
The twins extend over the whole gap of the shear cell with one twin always
located in the outer region of the gap, and the other twin always located in the
inner region of the gap. We could visualize twin boundary surfaces by using transmission
electron microscopy. In analogy to the plastic deformation of nanocrystalline metals under
high shear stress and high deformation rates we propose a deformation
twining mechanism for the formation of such macroscopic twins.