Simultaneous rheological, polarized light imaging, and
small-angle X-ray scattering experiments (Rheo-PLI-SAXS) are developed [1].
We highlight how the method can be used to study  the multiscale orientation [2] of hierarchical
systems in simple shear with a specific case study on cellulose nanocrystals
[3].  Notably, it is observed that
mesoscale alignment in the flow direction does not develop simultaneously
across nano-micro lengthscales in sheared suspensions of rod-like
chiral-nematic (meso) phase forming cellulose nanocrystals. Rather, with
increasing shear rate, orientation is observed first at mesoscale and then
extends to the nanoscale, with influencing factors being the aggregation
state of the hierarchy and concentration. In biphasic systems, where an
isotropic phase co-exists with self-assembled liquid crystalline mesophase
domains, the onset of mesodomain alignment towards the flow direction can
occur at shear rates nearing one decade before a progressive increase in
preferential orientation at nanoscale is detected. If physical confinement
prevents the full formation of a cholesteric phase, mesoscale orientation
occurs in shear rate ranges that correspond to de-structuring at nanoscale.
Interestingly, nano- and mesoscale orientations appear to converge only for
biphasic suspensions with primary nanoparticles predominantly made up of
individual crystallites and in a high-aspect ratio nematic-forming thin-wall
nanotube system. The nano-micro orientation propagation is attributed to
differences in the elongation and breakage of mesophase domains.