Rheo-NMR phenomena of wormlike micelles

Abstract

Using a combination of rheology and nuclear magnetic resonance (NMR) spectroscopy/velocimetry we demonstrate the existence of shear banding fluctuations under Couette flow of the micellar system 10% w/v cetylpyridinium chloride and sodium salicylate (CPyCl–NaSal) molar ratio 2 : 1 in 0.5 M NaCl in either ¹H₂O or ²H₂O, using both time-averaged and real-time measurements. These shear banding fluctuations are consistent not only with the shear stress fluctuations observed in rheological measurements but also with fluctuations in the change of the constrained fraction of the amphiphile chain (Δf_c) observed in ¹H-NMR spectroscopy experiments. Using ²H-NMR spectroscopy on a deuterated probe molecule (n-decane) located in the wormlike micellar interior, direct measurement of the shear-induced nematic phase transition is reported.