The influence of the cationic polyelectrolyte poly(diallyldimethylammonium chloride) on structure formation in the inverse micellar region (L2 phase) of the ternary system 3 (N,N-dimethyldodecylammonio)propanesulfonate/alcohol/water has been investigated. Up to a polymer concentration in the aqueous phase of 10 wt %, an isotropic phase still exists. As the chain length of the alcohol component increases, the isotropic phase region is reduced and shifted in direction to the water corner. The isotropic polyelectrolyte-modified L2 phase of the heptanol-based microemulsion has been studied in much more detail by means of conductometric, rheological, and differential scanning calorimetry measurements. The polyelectrolyte-modified microemulsion phase shows a characteristic low shear viscosity and Newtonian flow behavior. The characteristic features of the nonpercolated microemulsion droplets are the low conductivity and the disappearance of bulk water. One can conclude from the experimental data that the individual nonpercolated polyelectrolyte-stuffed microemulsion droplets are approximately uniform in size. In addition, the area of the polyelectrolyte-modified inverse microemulsion phase with heptanol and octanol depends on the temperature. This means that the area of the L2 region can be increased by the temperature being increased from room temperature to 40degreesC. This behavior can be explained by a change in the bending elasticity of the surface film induced by Coulombic interactions between the functional groups of the polyelectrolyte and the surfactant head groups. (C) 2003 Wiley Periodicals, Inc.