A Study of the Microstructure of a Four-Component Nonionic Microemulsion by Cryo-TEM, NMR, SAXS, and SANS

Abstract

One recently reported application of microemulsions is as a fire-resistant hydraulic fluid where efficacy and stability depend among other factors upon the water-solubilizing capacity of the microemulsion and on the relative concentration of the surfactant. A model for such a microemulsion system has been studied using cryo-transmission electron microscopy (cryo-TEM), 1 H NMR self-diffusion, and small angle X-ray (SAXS) and neutron scattering (SANS). The phase behavior of the system containing a 1:1:2 oil:alcohol: surfactant weight ratio is characterized by a single continuous microemulsion region starting from a solution containing no water and approaching the water corner. Along this dilution line, a structural transition sequence: oil drops f short range, noncontinuous lamellar microstructure f weakly hydrated aggregates is inferred as the water concentration is decreased. The local lamellar microstructure, i.e., stacks of surfactant sheets, oil, and water, randomly oriented in space without the long range correlations that characterize a lamellar liquid crystal is imaged for the first time.

Water Solubilization in Nonionic Microemulsions Stabilized by Grafted Siliconic Emulsifiers

“…Such a unidimensional expansion was also detected in our previous studies on concentrated microemulsions stabilized with ethoxylated surfactants (14,22). It suggests that the aggregate has a quasi-lamellar structure of surfactant and water, randomly oriented in the continuous oil phase.…”

“…• C with instrumentation described previously (14). Scattering profiles of microemulsions, in which there is a particular repeating distance, contain a single broad peak at q = 0 (where q = 4π sin θ/λ; 2θ is the scattering angle and λ = 1.54Å).…”

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.…”

Oxidation Catalysis by Enzymes in Microemulsions

“…This is due to the microemulsion's transparency allowing the application of photometric methods, which gives to these formulations a big advantage over other non-conventional systems. Since the late 1980s microemulsions have been extensively studied, on account of their microstructure properties, using different methods such as NMR (Nuclear Magnetic Resonance) [10], TEM (Transmission Electron Microscopy) [11], SAXS (Small-angle X-ray scattering) [12], SANS (Small-angle neutron scattering) [13], DLS (Dynamic Light Scattering) [14], and EPR (Electron Paramagnetic Resonance) [15].…”