Study on conductivity property and microstructure of TritonX-100/alkanol/n-heptane/water microemulsion

The validity of percolation theories on TritonX-100/heptane/alkanol/water W/O (water-in-oil) microemulsion has been investigated based on conductivity analysis. The experiment results have proved that the microemulsion follows both Bernasconi–Weismann (BW) and effective medium theory with dipole–dipole interaction (EMTDD, clusters) theories in the water content range from W0 = 1 to W0 = 7. The results here are different from the reported microemulsions with CTAB, AOT or SDS as ionic surfactant and alkanols as cosurfactants, and those microemulsions always follow effective medium theory (EMT) perfectly. This suggests that nonspherical surfactant aggregates and droplet clusters exist in the microemulsion solution due to the dipolar interaction between the dispersed droplets. The size of water pool, the hydrodynamic diameter of droplet, and the number of surfactant and cosurfactant per droplet have been evaluated according to the two validated theories. The dynamic state and the calculated size distribution of droplets are agreed with the results detected by dynamic light scattering technique. The research has indicated that the percolation theories are also adaptable to nonionic surfactant microemulsions with low water content and the structure parameters of droplets can be calculated by the effective theories.