PHASE-TRANSITIONS IN ENTANGLEMENT NETWORKS OF WORMLIKE MICELLES

The condition of isotopic to liquid Crystalline phase transitions in entanglement networks of a wormlike micellar system was examined. The system was aqueous solutions of cetyltrimethylammonium bromide and sodium salicylate and showed profound viscoelastic behavior. The plateau modulus, G(N)(0), was proportional to C-D(22), where C-D is the concentration of the surfactant, like semidilute polymer solutions. However, at C-D = 0.6 M the system showed a phase transition to liquid crystalline phase, and the proportionality in G(N)(0) did not hold any more above C-D congruent to 0.4 M. C-D dependence of the contour:length between entanglement points, L(e) (proportional to C-D(-1.1)), was also quite similar to that of semidilute polymer solutions below C-D congruent to 0.4 M. At the concentration of phase transition, L(e) was shorter than-the size of an equivalent random flight (Kuhn) segment of the micelle. When the micellar portion between entanglement points becomes shorter and loses characters of the random flight chains, the whole system exhibits a phase transition to the liquid crystalline state.