Small angle neutron scattering investigation of structural inversion in a three-component ionic micro-emulsion

Abstract

We have made an extensive investigation of the phase diagrams and the associated mierastructure of a pseudo-temary system AOT/water (0.6 wt% NaCl)/ decane. This micro-emulsion system shows, for a surfactant concentration in excess of 6 wt%, acharacterkticphase progressionfrom a water-in-oil(w/o) micro-emulsion in coexistence with excess water at low temperatures to an oil-in-water (OlW) microemulsion in coexistence with excess oil at high temperatures through a onephase micro-emulsion in the intermediate temperatures. Thus, one expects a StNcturd invusion to occur somewhere in the one-phase &d.We haw performed extensive small angle neutron scattering (SANS) measurements to study the pathway of such a structural inversion in this micro-emulsionsystem when there are comparable a m o u t s of oil and water in the system, and when the volume fraction of water is much higher than that of oil. In the former ease, we observed the inversion of the w/o to the olw micro-emulsions tlmugh an intermediate bicontinuous one-phase mi-emulsion.In the latter case, we show that the inversion takes pkce through a pathway of L3-Lo-L1 as temperature increaser. Particular emphasis is put on analyses of the interfacial structure in different mic-emulsion p h a s .

Magnetic microemulsions based on magnetic ionic liquids

“…The high scattering intensity, especially for about equal contents of oil and MRTIL, and the moving of the scattering curves to lower q prove the existence of relatively large, microphase seperated, domains, as typically observed for microemulsions. Similar scattering patterns have been observed for conventional microemulsions 41,42 and also for ones containing RTIL. [2][3][4]32 It is interesting to note that the degree of ordering is substantially lower for the MRTIL rich region as evidenced by the absence of a correlation peak.…”

1H NMR Study of a U-Type Nonionic Microemulsion

“…Additional information may be inferred from the rapid decay of the f [3] with the increase in water content (Fig. 7).…”

“…For a fast exchange condition existing where i stands for bulk (neat) water or free water in the between the bound and bulk regions, the following relation microemulsion sample, N i is the number of protons per cm 3 , holds (32), and D i is similarly the appropriate self-diffusion coefficient. K is a known constant and b is the distance of the closest approach between protons belonging to two different water 1 emulsions, N should be calculated from the actual water content of the microemulsion multiplied by f F from Eq.…”

“…nol and the surfactant to D obs must be taken into account No conceivable major conformational change like intramo-and the corrected D w values are calculated from Eq. [3] by substituting the measured D obs as well as the appropriate lecular folding of the hydrophobic chain into the vicinity of the hydrophilic EO groups seems likely to occur in our D p and D s values of Eq. [2].…”

“…methods (1,3,4), conductivity (5), electron microscopy (6), and fluorescence quenching (7,8), have been used to To gain additional information about the behavior of this clarify the phase behavior and the structure of microemulcomplicated model system upon dilution with water, we consions. All of these methods have their merits and drawbacks.…”