Investigation on solvent casting films of surfactant-encapsulated clusters.
The surfactant-encapsulated cluster (SEC) composed of a hydrophobic dimethyl dioctadecyl ammonium (DODA) shell and an encapsulated hydrophilic polyoxoanion core can form casting films. The structure of the casting film is influenced by evaporation rates of organic solvent. When the casting films are prepared by slow evaporation of chloroform, the alkyl chains are considered to possess a partial interdigitation, and the interdigitated length is 1.6 nm. The casting film structure is characterized by scanning force microscopy (SFM), Fourier transformation infrared (FT-IR), wide-angle X-ray diffraction, and differential scanning calorimetry (DSC).
Surfactant-encapsulated clusters (SECs): (DODA)20(NH4)[H3Mo57V6(NO)6O183(H2O)18], a case study.
We present a comprehensive study of the partially reduced polyoxomolybdate [H3-Mo57V6(NO)6O183(H2O)18]21-encapsulated in a shell of dimethyldioctadecylammonium (DODA) surfacmolecules. Treatment of an aqueous solution of (NH4)21[H3Mo57V6-(NO)6O183(H2O)18] . 65H2O (1a) with a trichloromethane solution of the surfactant leads to instant transfer of the encapsulated complex anion into the organic phase. Results from vibrational spectroscopy. analytical ultracentrifugation, small-angle X-ray scattering, transmission electron microscopy, elemental analysis, and Langmuir compression isotherms are consistent with a single polyoxometalate core encapsulated within a shell of 20 DODA molecules. The molar mass of the supramolecular assembly is 20249 gmol(-1) and the diameter is 3.5 nm. A material with the empirical formula (DODA)20(NH4)[H3-Mo57V6NO)6O183(H2O)18] (2) was isolated as a dark violet solid, which readily dissolves in organic solvents. Slow evaporation of solutions of 2 on solid substrates forces the hydrophobic particles to aggregate into a cubic lattice. Annealing these so-formed films at elevated temperature causes de-wetting with terrace formation similar to liquid crystals and block copolymers. Compound 2 forms a stable Langmuir monolayer at the air-water interface; Langmuir-Blodgett multilayers are readily prepared by repeated transfer of monolayers on solid substrates. The films were characterized by optical ellipsometry, Brewster angle microscopy, transmission electron microscopy, and X-ray reflectance.
Tube-like Nanostructures Composed of Networks of Complementary Hydrogen Bonds
In the present study we prepared amphiphilic supramolecular architectures that are dispersible in organic media by employing a hydrogen-bond-mediated aromatic sheet as the strongly interacting (solvophobic) unit and alkyl chains as the solvophilic unit. The general strategy described in this paper would be extended to the design and synthesis of a wide range of mesoscopic superstructures with specified internal organizations and surface characteristics. 12 refs., 3 figs.