Entanglements in a Threadlike Micellar System As Studied by Dielectric Relaxation

The presence of contact (or entanglement) points in an aqueous threadlike micellar system consisting of equimolar cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) was confirmed using a dielectric relaxation measurement covering the frequency (ω) range from 6.3 × 10 6 to 6.3 × 10 9 rad s - 1 . The rotational relaxation mode of an ionic pair formed by CTA + and Sal - in a threadlike micelle was around ω ∼ 10 9 rad s - 1 . The magnitude of concentration-normalized relaxation strength for the rotational relaxation mode decreased, while that of a relaxation mode around ω ∼ 2 × 10 8 rad s - 1 increased with the concentration ( c D-S ) of CTAB and NaSal at c D-S > 30 m mol kg - 1 . However, the concentration-normalized relaxation strength for other relaxation modes did not change. These findings suggest that the rotational motion of the ionic pair is strictly interrupted and slowed at contact points between threadlike micelles owing to interaction between two portions constructed by ionic pairs on the micellar surface.