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).

Redox-active organic–inorganic hybrid polyoxometalate micelles

“…12 In this covalent approach, the inorganic POMs are functionalised with organic groups, such as long aliphatic alkyl chains, to form organicinorganic hybrid molecules which can assemble to form micellar, vesicular and liquid crystal-like states. Polarz, Song, Cronin, Liu and their co-workers have pioneered the field of covalently functionalized polyoxometalate-surfactants, and shed light on their complex architectures and self-assembly, [13][14][15][16][17][18][19][20][21][22][23][24] _ENREF_15 however, relatively little is known about the physicochemical properties of the nanoscale hybrid assemblies, and in particular the translation of POM functionality across the scales, from molecular to supramolecular and bulk.…”

Aggregation‐Induced Improvement of Catalytic Activity by Inner‐Aggregate Electronic Communication of Metal‐Fullerene‐Based Surfactants

“…Recently, more and more papers describe advanced surfactants with properties beyond simple amphiphilic properties . Our group has specialized in the synthesis of surfactants equipped with functional, metal‐containing head groups, and several examples of catalytically active surfactants have already been published by us . Important preliminary work of relevance to the current work is centered on fullerene‐based surfactants that evaluated their self‐assembly behavior and the related beneficial effect of self‐assembly on their properties …”

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“…If such patients need to be given medication, the stents can be a good source for drug release. Drug-eluting stents have been long investigated for the treatment of lesions and other cardiovascular problems 35 . Drug-loaded micelles can potentially be coated on stents to achieve sustained drug release in patients.…”