PHASE-TRANSITIONS IN ENTANGLEMENT NETWORKS OF WORMLIKE MICELLES

The condition of isotopic to liquid Crystalline phase transitions in e ntanglement networks of a wormlike micellar system was examined. The s ystem was aqueous solutions of cetyltrimethylammonium bromide and sodi um salicylate and showed profound viscoelastic behavior. The plateau m odulus, G(N)(0), was proportional to C-D(22), where C-D is the concent ration of the surfactant, like semidilute polymer solutions. However, at C-D = 0.6 M the system showed a phase transition to liquid crystall ine phase, and the proportionality in G(N)(0) did not hold any more ab ove C-D congruent to 0.4 M. C-D dependence of the contour:length betwe en entanglement points, L(e) (proportional to C-D(-1.1)), was also qui te 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 mic elle. When the micellar portion between entanglement points becomes sh orter and loses characters of the random flight chains, the whole syst em exhibits a phase transition to the liquid crystalline state.