Free‐Standing Phytantriol Q224 Cubic‐Phase Films: Resistivity Monitoring and Switching

Phytantriol Q224 cubic phase, as a bi-continuous meso-structured material stable in contact with aqueous electrolyte, has found applications in drug delivery and cosmetics and is employed here as a free-standing film separating two aqueous compartments in order to study (i) ion conductivity (at low potential bias within ±0.8 V), (ii) conductivity switching effects (at high potential bias beyond ±0.8 V), and (iii) phase switching effects (as a function of temperature). A microhole of approximately 20 microm diameter in a 6 microm thick poly-ethylene-terephthalate (PET) film is employed as support coated with phytantriol (on a single side or on both sides) in contact with aqueous electrolyte phase on both sides in a classic 4-electrode measurement cell. The conductivity of the phytantriol phase within the microhole is shown to be ionic strength, applied potential, time/history, and temperature dependent. The experimental data for asymmetric phytantriol deposits are indicative of a microhole resistance that can be switched between two states (high and low resistance associated with a filled or empty microhole, respectively). When heating symmetrically applied films of phytantriol, Q224 to HII phase transition linked to a jump to higher specific resistivity is observed consistent with differential scanning calorimetry (DSC) data for this phase transition.