Impact of Molecular Structure on Assembly of Microemulsions in Porous Electrodes

Microemulsions (ME) have applications in a variety of sectors from food products to pharmaceuticals and healthcare to energy materials, with recent interest in their electrochemical functionality for use in energy-related devices. MEs consist of oil, water, and surfactants that comprise of a hydrophilic head and a hydrophobic tail. From a molecular perspective, their functionality is dependent on the ordering and packing of the surfactant at the oil-water interface. For instance, our recent studies of Tween-20/water/toluene MEs probed the ternary phase diagram with cyclic voltammetry, conductivity, SANS, and NMR. The electrochemical techniques have shown there is facile electron transfer from ferrocene in the oil phase and the electrochemical kinetics are sufficient for use in an energy storage device. Similar studies are underway for the Brij-35/water/toluene system, as both Brij-35 and Tween-20 are non-ionic surfactants with similar structure, except Brij-35 is a linear molecule, while Tween-20 is branched. Thus, the local packing and ordering of Tween-20 at the oil-water interface will differ from that of Brij-35, which in turn may impact ionic transport across the interface. We are interested in understanding how this variation in molecular structure and local packing will impact the mesoscale structure and assembly of the ME and correlate this to its performance in an energy storage device.