MEASUREMENT OF THE ORIENTATIONAL BINDING OF COUNTERIONS BY NUCLEAR-MAGNETIC-RESONANCE MEASUREMENTS TO PREDICT DRAG REDUCTION IN CATIONIC SURFACTANT MICELLE SOLUTIONS

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.