Biologically inspired polyoxometalate–surfactant composite materials. Investigations on the structures of discrete, surfactant-encapsulated clusters, monolayers, and Langmuir–Blodgett films of (DODA)40(NH4)2[(H2O)n ⊂ Mo132O372(CH3CO2)30(H2O)72] †

Abstract

A detailed analysis of the supramolecular architecture of the nanoporous surfactant-encapsulated cluster (SEC) with the empirical formula (DODA) 40 (NH 4 The open framework architecture of the Keplerate cluster is investigated by means of small angle neutron scattering (SANS) in CDCl 3 solutions containing discrete SECs. A simplifying core-shell model of 1 is developed, which describes the SEC as a solvent-filled nanocavity, surrounded by two concentric shells (a first polyoxometalate shell of 2.96 nm outer diameter, and a consecutive surfactant shell of 6.18 nm outer diameter, respectively). The model is successfully applied to probe the content of H 2 O/D 2 O guest molecules in the Keplerate host. Different surface analytical techniques are applied to characterize the hierarchical structures of monolayers and thin films of 1. Monolayers at the air-water interface are investigated by means of optical ellipsometry and Brewster angle microscopy. Electron density profiles of the monolayers of 1 are gained from synchrotron X-ray reflectance (XRR) measurements that provide further evidence for the supramolecular core-shell architecture of the SEC. Within the spatial resolution limits of these analytical methods, the current data support a monolayer model consisting of hexagonal close-packed arrays of discrete SECs, floating at the air-water interface. Langmuir-Blodgett (LB) transfer of compressed monolayers on to a solid substrate leads to homogeneous multilayers. In the XRR spectra of LB multilayers of 1 multiple Bragg reflections appear, thus indicating an intrinsic tendency of the SECs to adapt a 3-dimensional, highly ordered solid state structure. Considering the huge variety of structurally different polyoxometalates and the possibility to tailor the surfactant shell by means of classic organic synthesis, the selforganization of hierarchically structured thin films and solids based on SECs bears promising perspectives towards the engineering of functional materials. † Based on the presentation given at Dalton Discussion No. 3,

Investigation on Solvent Casting Films of Surfactant-Encapsulated Clusters

“…This value is much larger than layer thickness measured from SFM. The difference between them can naturally and rationally be understood to the strong distortion of the alkyl chains of SEC-1 on hydrophilic mica surface because of the unfavorable energies (20).…”

Linking Giant Molybdenum Oxide Based Nano‐Objects Based on Well‐Defined Surfaces in Different Phases

“…self-aggregation, surface adhesion, wetting behavior) in a predictable manner. Some related investigations [13,14] are reviewed here, also deliberately with respect to some details.…”

Metallo-supramolecular modules as a paradigm for materials science

“…This preparation scheme permits the characterization of the materials used in each step. This approach has also been successfully used to encapsulate POMs with dendritically branching amphiphiles [141][142][143][144]. These results show that surfactant encapsulation is widely applicable to different POM clusters and amphiphilic systems.…”