Electric Conductivity near the Percolation Transition of a Nonionic Water-in-Oil Microemulsion

The electric conductivity of a nonionic water-in-oil microemulsion has been measured in the presence of small amounts of carrier electrolyte. Two distinct regimes can be distinguished: the conductivity increases linearly for small nanodroplet concentration, while it decreases above a critical value. The qualitative change occurs close to a concentration where the system is known to have formed a system-spanning nonconducting cluster of nanodroplets. This behaviour of the conductivity is shown to agree well with predictions of percolation theory for aggregating charged nanodroplets.