Comment on the concentration dependence of isotropic-nematic transition temperatures in micellar systems

Recent magnetic birefringence experiments have measured the temperature difference $T_0$-$T^{\mathrm{*}}$=ΔT as a function of concentration (amphiphile volume fraction φ) for the micellar system cesium perfluoro-octanoate–water. Here $T_0$ is the isotropic-nematic transition temperature and $T^{\mathrm{*}}$ is the ‘‘Landau’’ temperature at which the birefringence (and light scattering intensity, etc.) would diverge if the first-order phase transformation did not intervene. By treating explicitly the competing roles of attractive and repulsive forces, we account for ΔT being much smaller than that in thermotropic liquids and for its strong increase with φ.