Rheo-NMR of unusual shear banded flow in wormlike micelles

Friday, September 18, 2009 - 9:00am - 9:45am
EE/CS 3-180
Paul Callaghan (Victoria University of Wellington)
In the study of shear banding phenomena in wormlike micelles, Rheo-NMR has
proven of especial value, not only indicating the clear existence of shear
bands, but also that they are associated with fluctuations, and sometimes,
with molecular alignment. The subtlety of the correspondence (or lack of
correspondence) between birefringence effects and shear banded flow has also
been revealed. Recent measurements of shear-banded flow under Couette flow
of the micellar system cetylpyridinium chloride and sodium salicylate
(CPyCl/NaSal) indicate that shear banding fluctuations that are inconsistent
with the usual lever rule picture. We have also used Rheo-NMR to investigate
the flow and alignment properties of worm-like micelles formed by a 5% w/w
solution of the BASF difunctional block copolymer non-ionic surfactant,
Pluronic P105 in water along with 4.3% w/v 1-phenylethanol-d5. A variety of
bizarre shear-banding and alignment behaviours are observed, along with both
stable and fluctuating flows.
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