Switching electrical conductivity in an AOT–isooctane–water microemulsion through photodimerization of solubilized N-methyl-2-quinolone

Abstract

The electrical conductivity of microemulsions composed of Aerosol OT (AOT), isooctane and water as a function of temperature was studied in the absence and presence of N-methyl-2-quinolone (NMQ), and consequences of an in situ photodimerization of NMQ were investigated. A conductivity increase upon raising the temperature of a water-in-oil microemulsion indicates percolation. Percolation temperatures (T_p) can be influenced specifically by the addition of certain substances. Small amounts of solubilized N-methyl-2-quinolone induce lower T_p (by up to 9 K), and photodimerization of NMQ shifts T_p back to higher values. Consequently, the microemulsion can be switched from conducting to non-conducting without varying temperature or composition by exposing samples to UV light at λ > 310 nm. The effect can be reverted in part by irradiation at λ = 250 nm. Coumarin derivatives—structurally related to NMQ—show much slighter effects.