MEASUREMENT OF THE ORIENTATIONAL BINDING OF COUNTERIONS BY NUCLEAR-MAGNETIC-RESONANCE MEASUREMENTS TO PREDICT DRAG REDUCTION IN CATIONIC SURFACTANT MICELLE SOLUTIONS
Bc. Smith et al., MEASUREMENT OF THE ORIENTATIONAL BINDING OF COUNTERIONS BY NUCLEAR-MAGNETIC-RESONANCE MEASUREMENTS TO PREDICT DRAG REDUCTION IN CATIONIC SURFACTANT MICELLE SOLUTIONS, Journal of rheology, 38(1), 1994, pp. 73-83
Quaternary ammonium cationic surfactants with appropriate counterions
are viscoelastic friction reducers and can reduce pumping energy requi
rements, increase water throughput, or reduce pump size Or pipeline di
ameter in closed loop district heating and cooling systems. Drag reduc
tion occurs when rod-like micelles are present. Isomers of ortho-, met
a-, and para-hydroxy-benzoate and chloro-benzoate were investigated by
Fourier transform nuclear magnetic resonance (FT NMR). The orientatio
n of each counterion near the micellar surface was inferred using the
proton chemical shifts. NMR peak broadening was used to infer which co
unterions induce rod-like micellar aggregates and the occurrence of vi
scoelasticity. Drag reduction was only observed in the solutions which
demonstrated peak broadening. The NMR chemical shift data indicate th
at only those counterions whose structure permits orienting their hydr
ophobic and hydrophilic portions in their preferred environments can s
tabilize the micellar interface to facilitate the sphere-to-rod transi
tion and induce drag reduction. Thus, FT-NMR peak broadening and chemi
cal shift data can be used to predict the drag-reducing capability of
cationic surfactant-counterion systems.