Alkaline Lyotropic Silicate−Surfactant Liquid Crystals

Abstract

Multinuclear (2H, 13C, 29Si, 81Br) magnetic resonance spectroscopy, small-angle X-ray scattering, and polarized optical microscopy techniques have been used to investigate molecular and mesoscopic organization in silicate−surfactant lyotropic liquid crystals with hexagonal and lamellar morphologies under highly alkaline conditions. Such systems cooperatively self-assemble following the addition of a basic aqueous solution containing anionic silicate oligomers (e.g., double-four-ring species) to an isotropic micellar solution of cationic surfactant molecules (e.g., cetyltrimethylammonium bromide). Important similarities and differences are shown to exist between multicomponent silicate−surfactant and conventional binary lyotropic liquid crystals. Under highly alkaline conditions, the silicate−surfactant systems possess the characteristics of ordinary lyotropic liquid crystalline systems, though the balance of forces underlying their self-assembly is complicated by the richness of the aqueous silicate chemistry. This is the first comprehensive description of lyotropic silicate−surfactant liquid crystalline behavior, from which detailed insight is obtained into the molecular factors governing inorganic−organic mesophase formation in aqueous media.

One-Step Synthesis of Alkyltrimethylammonium-Intercalated Magadiite

“…Instead, the precursors transform to more organized MCM-41 (molecular sieve) structures. Also, when acetic, hydrochloric, or hydrofluoric acids are used, only MCM-41 mesophases are obtained, This result is probably related to the presence of silicon in the precursor as a cubic octamer, Qs 3, which is preferentially bound by the CTA + supramolecular arrangement (Firouzi et al, 1997;Pastore et al, 1999). This anion behaves as a chelate ligand, therefore bringing additional stability to the organic-inorganic composite.…”

Synthesis,Mechanisms and Different Applications of Mesoporous Materials Based on Silica and Alumina

“…Firouzi et al (45) showed that there is a preferential bonding of ammonium head group of alkyl trimethylammonim surfactant to D4R silicate anions at high pH. This was proved by the formation of D4R in solution of silicate anions which did not contain D4R species.…”

“…Apart from these two models, another model was proposed by Firouzi et al (45) , known as "silica tropic liquid crystals". They investigated the effect of electrolyte on miceller phase transitions through 1 H, 29 Si NMR spectroscopy and neutron scattering study of CTAB phase transition.…”

Sustained Drug Release on Temperature-responsive Polymer Hybrid Nanoporous Silica Composites

“…[1][2][3][4] Many investigations have been explored on the preparation of nanoporous materials with novel chemical composition, 5 on the fundamental understanding of the reaction processes, [6][7][8] and on the potential applications such as catalysis, [9][10][11] and separation technology 12,13 expected to open up further application possibilities. Interest in the structure of the pore network is necessarily concomitant with the formation of different structures including a hexagonal, cubic, and lamellar structure.…”

“…4,6 In a typical preparation of the nanoporous silica, 4.0 g of Pluronic P123 was dissolved in 30 g of water and 120 g of 2M-HCl, and then 8.5 g of tetraethyl orthosilicate (TEOS) was added into the solution at 40 °C. The mixture was aged in a bomb at 120 °C overnight without stirring.…”