ANOMALOUS ORDERING IN WORMLIKE MICELLES UNDER ELECTRIC-FIELD

The rotational dynamics of cetyltrimethylammonium tosylate (CTAT) mice llar solutions using transient electric birefringence (TEB) are report ed. The birefringence signal is resolved into three components-a norma l one, related to the alignment of free or partially free cylindrical micelles with the field, an anomalous one of opposite sign, observed f or concentrations around the overlap concentration, c, and a third on e of same sign as the normal one observed for c > c. The effects of s urfactant concentration and temperature on these components are studie d. The origin of the anomalous signal is analyzed by combining recentl y proposed pictures by Hoffmann and by Cates. In the latter case, disk like clusters are suggested to exist around c. The dimensions of thes e clusters are estimated in two different ways: using the rotational d iffusion of disklike clusters and considering the polarization of a ch arge cloud of the counterions. They are found to agree reasonably. The anomalous birefringence exhibits a maximum when plotted against the s quare of the electric field. It obeys a master curve, independent of c oncentration, when data are normalized by the maximum values.