X-ray diffraction study of mesophases of cetyltrimethylammonium bromide in water, formamide, and glycerol

Abstract

In this work we investigated phase diagrams of CTAB and different polar solvents such as water, formamide, and glycerol in order to compare the effects of a nonaqueous solvent on the existence of intermediate phases. A small-angle X-ray scattering setup was used to observe the diffraction peak corresponding to the high values of the phase parameters and their transformations. We developed a method for rapid and continuous observation of the surfactant-solvent system over their transitions from the micellar to the lamellar phase. The following sequence of intermediate phases was identified in the CTAB/water system: hexagonal-monoclinic (close to a centered rectangular phase)-cubic-lamellar. Comparison with the results from CTAB/formamide and CTAB/glycerol systems showed the same sequence (except that the monoclinic phase existence was only found with water), but the existence regions of these phases are different and the parameters are smaller.

Control of the Long-axis Length of Gold Nanorods through Temperature Variation

“…Next, we discuss the effects of the self-assembled structure of the surfactant molecules on the elongation of the gold nanorods. According to the phase diagram for an aqueous HTAB solution, 10 the phase boundary between the isotropic micelles and hydrated solid phase, i.e., a lamellar structure, exists at around 20°C at this concentration. In other words, above 20°C, the selfassembly of surfactants forms the micellar structure, whereas below 20°C, the hydrated solid structure appears.…”

Template-mediated ontogenesis: A novel approach to mesomorphic materials

“…The liquid crystalline surfactant template actually forms during the reaction, the phase transition from a micellar phase being driven by the production of multidentate silica ligands produced from the hydrolysis of silica alkoxides. The periodicity in these materials is - [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] A and the pore size in the hexagonal phase is -25-30 A. Zeolites have pore sizes generally smaller than 8 A so these materials fill a size range that cannot be achieved by other techniques. After the silica-surfactant system assembles into the liquid crystalline phase, (-4 s at ambient temperature) condensation of the silica occurs to form a nearly fully bonded framework in a few minutes.…”

“…The samples were aged 5 days. reported for the protic donor solvents glycerol, ethylene glycol, formamide, and N-methylformamide [48,49].…”

Preparation and Crystal Structure Determination of Sulphur Dioxide Solvate Crystals with Cetyl- and Dodecyltrimethylammonium Bromide

“…The main purpose for the use of ionic surfactants such as quaternary ammonium salts, e. g. cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB) or cetyltrimethylammonium chloride (CTAC), is to form spherical micelles in water, formamide, glycerol, or ammonia at concentrations above a critical micelle concentration [1,2]. The compounds contain a long hydrocarbon chain and a lyophilic head, which induce the formation of micelle structures.…”

“…In addition, ionic surfactants can form complexes with different aromatic hydrocarbons [3], phenol derivates [4 -6], guaiacol, 2-methylindole, skatole [7], and perchlorates [8] in aqueous solutions. In this paper, we report two new crystal structures of molecular complexes containing the common surfactants DTAB and CTAB and sulphur dioxide as the only solvate molecule: C n H 2n+1 N(CH 3 ) 3 · Br · SO 2 with n = 12 (1), and n = 16 (2). Due to the fact that single crystals of sufficient size and quality for single crystal diffraction could not be obtained, the crystal structures of 1 and 2 were determined from high-resolution powder diffraction on in situ synthesised microcrystalline samples.…”