Passing Current through Electrically Conducting Lyotropic Liquid Crystals and Micelles Assembled from Hybrid Surfactants with π-Conjugated Tail and Polyoxometalate Head

Abstract

The solvent-mediated ability for molecularly encoded self-assembly into states of higher order (micelles, lyotropic liquid crystals) embodies the basis for many applications of surfactants in science and society. Surfactants are used frequently in recipes for nanoparticle synthesis. Because ordinary surfactants comprise insulating constituents (alkyl groups as side-chains and charged organic heads), such nanostructures are wrapped in an electrically inactive barrier, and this is a large disadvantage for future developments in nanotechnology. Implications of micelles with electrically conducting walls made from either "metallic" or "semiconducting" surfactants are huge, also in other areas such as nanoelectrocatalysis or micellar energy storage. We cross this frontier by replacing not only the hydrophilic chain but also the hydrophilic head by electronically conducting entities. We report the synthesis of surfactants with oligo para-phenylene-ethynylene as a π-conjugated side-chain attached to a redox-active, inorganic polyoxometalate cluster as charged head. It is proven that electronic communication between head and tail takes place. Hybridization on the molecular level leads to the emergence of advanced surfactant features such as semiconductor properties (Egap = 2.6 eV) in soft lyotropic systems (micelles, liquid crystals).