Existence and Stability of New Nanoreactors:  Highly Swollen Hexagonal Liquid Crystals

Abstract

We report the preparation of direct hexagonal liquid crystals, constituted of oil-swollen cylinders arranged on a triangular lattice in water. The volume ratio of oil over water, rho can be as large as 3.8. From the lattice parameter measured by small-angle X-ray scattering, we show that all the oil is indeed incorporated into the cylinders, thus allowing the diameter of the cylinders to be controlled over one decade range, provided that the ionic strength of the aqueous medium and rho are varied concomitantly. These hexagonal swollen liquid crystals (SLCs) have been first reported with sodium dodecyl sulfate as anionic surfactant, cyclohexane as solvent, 1-pentanol as co-surfactant, and sodium chloride as salt (Ramos, L.; Fabre, P. Langmuir 1997, 13, 13). The stability of these liquid crystals is investigated when the pH of the aqueous medium or the chemical nature of the components (salt and surfactant) is changed. We demonstrate that the range of stability is quite extended, rendering swollen hexagonal phases potentially useful for the fabrication of nanomaterials. As illustrations, we finally show that gelation of inorganic particles in the continuous aqueous medium of a SLC and polymerization within the oil-swollen cylinders of a SLC can be conducted without disrupting the hexagonal order of the system.

Facile synthesis of pristine graphene-palladium nanocomposites with extraordinary catalytic activities using swollen liquid crystals

“…S8c,d respectively. The SAXS patterns of the samples showed three peaks, whose positions were in the ratio of 1:√3:2 and correspond respectively to (1 0), (1 1) and (2 0) diffraction planes of the hexagonal mesophases formed by the compact packing of cylindrical surfactant tubes 20 .…”

“…This seems quite unlikely as the diameter of the surfactant tubes were found to be 16.5 nm. The position of the first peak, q 10 in the SAXS pattern of the mesophase, allows the direct determination of the center–center distance between adjacent tubes (d c ) = (2/√3)(2п/q 10 ) 20 . The d c values for SLC-Pd and SLC-G1 were 16.35 and 16.5 nm respectively.…”

Conducting polymer nanostructures for photocatalysis under visible light

“…of PDPB nanofibres in hexagonal mesophases composed of oilswollen surfactant tubes arranged on a triangular lattice in water under ultraviolet irradiation 17,18 . The hydrophobic domain of the mesophases can accommodate high concentrations (up to 20wt.%) of 1,4-diphenylbutadiyne (DPB) monomer, which can directly polymerize by photoirradiation in the presence of a free-radical initiator (benzoin methyl ether, BME, 1%) 19 .…”

Radical polymerization behavior and molecular weight development of homologous monoacrylate monomers in lyotropic liquid crystal phases

“…Another useful method involves polymerization of nonmesogenic monomers within LLC media. In this approach, the LLC phase may be thought of as a “nanoreactor,” confining polymerization within hydrophobic or hydrophilic domains of the aggregate structure depending on monomer solubility . In addition to allowing low cost, this method provides great versatility.…”