Binary Phase Diagram of Water/Brij58 Studied by SAXS

Abstract

The phase diagram of the binary water/Brij58 system has been studied at constant temperature T = 20• C first by simple optical observation and then by small angle X-ray scattering. The small angle X-ray scattering patterns in the isotropic diluted phase are analyzed in a quantitative way by refining the experimental measurements with a model assuming hard spherical micelles in interaction. The micelles are described by a poly dispersed core-shell model and the interaction by the Perkus-Yevick hard-sphere model. The fitted parameters are analyzed in detail to determine the way polyoxyethylene blocks are hydrated with respect to the volumic fraction of water. In the more concentrated regime, the crystalline phases that are identified are the F m3m cubic, the 2D hexagonal and the lamellar phases. The structural parameters that describe each phases are analyzed and commented. The small angle X-ray scattering study is complemented by the determination of the temperature dependent liquid-solid transition by rheology.PACS: 81.30.−t, 61.05.C−, 64.70.dg IntroductionThe full understanding of the properties of surfactants when added to oil and water is of considerable interest given their tremendous applications in many scientific fields such as the design of hybrid mesoporous materials, drug delivery, or more prosaically industrial applications of detergents. Among widely used surfactants one finds the non-ionic surfactant of the Brij family characterized by a hydrophilic head made of polyoxyethylene (PEO) and a hydrophobic tail made of an alkyl chain. Quite surprisingly very little information is found in the literature about the phase diagram of the Brij58 (polyoxyethylene(20) cetyl ether). Apart from a neutron study of Brij58 micelles made by Sheffer et al. [1] by small angle neutron scattering and the study done by Mitchell on the phase behavior of polyoxyethylene surfactants with water, no real analysis of the phase diagram is available to the best of our knowledge [1][2][3].Our objective in this paper is to present the small angle X-ray scattering (SAXS) determination of the structures developed by the Brij58 when mixed with water from 5% to 95% in weight at a constant temperature of 20

Path-Dependent Preparation of Complex Micelle Packings of a Hydrated Diblock Oligomer

“…Previous studies of the phase behavior of C 16 E 20 relied solely on optical microscopy and low resolution SAXS to identify the LLC mesophases formed, thus precluding definitive morphology assignments. 39,41,42…”

“…Previous studies of the phase behavior of C 16 E 20 relied solely on optical microscopy and low resolution SAXS to identify the LLC mesophases formed, thus precluding definitive morphology assignments. 39,41,42 Figure 1 presents representative SAXS data for a series of aqueous LLCs formed by centrifugation in the concentration range 30−65 wt % C 16 E 20 , from which a phase map was constructed using data obtained during the first heating cycle for each composition. Figure 1A heating the as-formed FCC structure instead drives an orderto-order transition (OOT) to a pure body-centered cubic (BCC) morphology at T ≥ 60 °C.…”

“…Detailed sample preparation and data acquisition protocols are provided in the Supporting Information. Previous studies of the phase behavior of C 16 E 20 relied solely on optical microscopy and low resolution SAXS to identify the LLC mesophases formed, thus precluding definitive morphology assignments. ,, …”

Pickering Emulsions Stabilized by Nanoparticle Surfactants

“…SAXS experiments are performed in an Anton Paar SAXSess instrument (Graz, Austria) with a line-collimation system using a Cu K α source with a wavelength of 1.54 Å. The data are placed on an absolute scale by referencing to the scattering of pure water, which is known to have an absolute scattering of 0.0162 cm –1 . The scattering curves are subsequently desmeared using the Lake iterative method prior to data fitting with Igor macros developed at NIST. , The smeared scattering curves are also fit directly using the DANSE SansView software, and both methods result in identical fit parameters .…”

Structures, Electronic Properties, and Interactions of Cetyl Alcohol with Cetomacrogol and Water: Insights from Quantum Chemical Calculations and Experimental Investigations

“…Depending on the level of ethoxylation performed, this product could be available with repeat units ( n ) of polyethylene glycol in the range of 2–20, e.g., when n = 20, the product is commercially marketed as Brij-58. Cetomacrogol-1000 has been investigated as a solubilizer and emulsifying agent in cosmetic and pharmaceutical products. − Moreover, the physicochemical properties of cetomacrogol-1000-containing mixtures have gained much attention so far, e.g., the molar excess Gibbs energy of the mixed micelle formation between ionic surfactants (sodium cholate, sodium deoxycholate) and Brij (S10 and 58) described by the first-order Margules function, the phase diagram of the binary water/Brij58 system studied at 20 °C by both simple optical observation and small-angle X-ray scattering, the phase diagrams of pseudo-quaternary systems of cetyltrimethylammonium bromide (CTAB)/Brij-58/water/1-butanol (or 1-pentanol)/ n -heptane (or n -decane) at a fixed ω ([water]/[surfactant]) of 55.6 constructed at different temperatures (293, 303, 313, and 323 K) and different mole fraction compositions of Brij-58 ( X Brij‑58 = 0.5 and 1.0 in CTAB + Brij-58 mixture), a synergistic interaction of a mixed CTAB/C 16 E 20 micellar system evidenced experimentally and also supported by theoretical calculations using density functional theory (DFT), and micellization studies on binary mixtures of methionine with Brij-56 ( n = 10) and Brij-58 …”