THE MICROSTURCTURE AND LINEAR VISCOELASTICITY OF OTAC/NASAL WORMLIKE MICELLES

The formation, microstructure and linear viscoelasticity of wormlike micelles with octadecyl trimetryl ammoium chloride (OTAC)/sodium salicylate (NaSal) were analyzed with the method of rheology and freeze-fracture transmission electron microscopy (FF-TEM). It is shown that the long wormlike micelles with several micrometers are obtained if the mass ratio of the OTAC master solution to NaSal is 5:1. The linear micelle is dominated when the OTAC master solution weight content is 1.4%. The micelles begin to entangle with the increase of the OTAC solution concentration. When the weight content of OTAC master solution is 4% at a constant mass ratio, 5:1 of OTAC to NaSal, the minimum of entanglement length, l_e, may occur and the solution shows good viscoelasticity with a longer relaxtion time, 2.86 second. The entanglement wormlike micelles show the Maxwellian behavior at low frequency and the deviation occurs at high oscillation frequency. The deviation shows that the "breathing" and "Rouse-like" motions of wormlike micelles will dominate the stress relaxation process for the entanglements of micelles. It is a solely characteristic stress relaxation mechanism of wormlike micelles at high oscillation frequency.