Search results for "Microemulsion"
showing 10 items of 99 documents
A simple method to prepare solid nanoparticles of water-soluble salts using water-in-oil microemulsions
2000
A new and simple method to prepare solid nanoparticles of water-soluble salts using water-in-oil microemulsions is described. In particular, starting from water/sodium bis(2-ethylhexyl)sulfosuccinate/n-heptane microemulsions carrying inside the aqueous core of the reversed micelles some water-soluble salts [CaCl2, Na2HPO4, Cu(NO3)2], after evaporation of the volatile components (water and apolar organic solvent), the resulting inorganic salt/surfactant composites were found to be totally dispersible in pure n-heptane. The presence of nanoparticles in these resuspended composites was ascertained by transmission electron microscopy observation of samples obtained by gentle evaporation of the …
Efficiency Boosting of Surfactants with Poly(ethylene oxide)-Poly(alkyl glycidyl ether)s: A New Class of Amphiphilic Polymers
2020
Twenty years ago, it was found that adding small amounts of amphiphilic block copolymers like poly(ethylene propylene)-co-poly(ethylene oxide) (PEP-b-PEO) to microemulsion systems strongly increases the efficiency of medium-chain surfactants to solubilize water and oil. Although being predestined to serve as a milestone in microemulsion research, the effect has only scarcely found its way into applications. In this work, we propose new types of efficiency boosters, namely, poly(ethylene oxide)-poly(alkyl glycidyl ether carbonate)s (PEO-b-PAlkGE) and their "carbonated" poly(ethylene oxide)-poly(carbonate alkyl glycidyl ether) analogs. Their synthesis via anionic ring-opening polymerization (…
Rheological properties of progesterone microemulsions: Influence of xanthan and chitosan biopolymer concentration
2008
In this preformulations study, rheological properties of microemulsions with progesterone (1%) were studied to analyze the effect of xanthan and chitosan at different concentrations (0.5–3%). Steady shear and oscillatory rheological properties were analyzed using a controlled stress rheometer. Steady shear data were satisfactorily adjusted to the Carreau model. For all preparations, shear-thinning behavior was observed. Zero shear viscosity (η0) increased with the biopolymer concentration. The results from dynamic experiments showed the behavior of all preparations with xanthan gum and those of chitosan to be characteristic of weak gels and liquid-like solutions, respectively. The correlati…
Interaction between a water-in-oil microemulsion and a linear-dendritic poly(propylene oxide)–polyglycerol block copolymer
2011
We present small angle scattering and dielectric spectroscopy results on the influence of an amphiphilic diblock copolymer on the structure and dynamics of a microemulsion. We use a water-in-oil (w/o) droplet microemulsion based on the anionic surfactant AOT (sodium bis(2-ethylhexyl) sulfosuccinate), that forms spherical water droplets coated by a monolayer of AOT dispersed in the continuous oil matrix. The studied polymer consists of a hydrophobic poly(propylene oxide) (PPO) block and a hydrophilic hyperbranched polyglycerol with 74 glycerol units (NG74). Combining small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) we find that the droplet structure is preserved …
Physicochemical Properties of Copper(II) Bis(2-ethylhexyl) Sulfosuccinate Reversed Micelles
1998
Abstract Measurements of some physicochemical properties (density, viscosity, conductance, UV–vis spectra, IR spectra) of the water/copper(II) bis(2-ethylhexyl) sulfosuccinate (Cu(DEHSS) 2 )/CCl 4 microemulsions, at a fixed surfactant molal concentration ([Cu (DEHSS) 2 ] = 0.05003 mol kg −1 ), as function of the molar ratio R ( R = [water]/[DEHSS − ]) have been performed at 25°C. Information on some structural and dynamical properties of the water-containing Cu(DEHSS) 2 reversed micelles and of their evolution with R are derived from the experimental results. The comparison with the same properties of water-containing sodium bis(2-ethylhexyl) sulfosuccinate reversed micelles allows to evide…
Electrical conductivity and permittivity of water-AOT-n-heptane microemulsions
1995
Measurements of the electrical conductivity and of the complex permittivity of water-sodium bis(2-ethylhexyl) sulfosuccinate (AOT)-n-heptane microemulsions are reported. The experimental results are rationalized in terms of a hopping mechanism of AOT anions within clusters of reversed micelles. The dependence of the hopping rate and of the cluster dimensions upon the ratio [water]/[AOT] and temperature is discussed.
PolyAT chemical denaturation in w/o microemulsion
2004
CD and UV spectroscopies have been used to investigate the effects caused by the addition of either strong acid-or base-containing microemulsions on the behaviour of the synthetic polynucleotide polyAT entrapped in the aqueous core of a cationic quaternary water-in-oil microemulsion (μE). The titrations were performed in the presence of variable concentrations of NaCl, in the range 0.00 to 0.60 M. In both cases, the primary effect was the reversible transition from B-double helix to random coil of the guest polynucleotide. However, in the microemulsive medium, the number of moles of protons (RH) and hydroxide ions (ROH) per mole of titrable sites are independent of the salt concentration bu…
Phospholipid-based reverse micelles.
1990
Physicochemical investigations on the aggregation of phospholipids (mainly phosphatidylcholines) in organic solvents are reviewed and compared with the aggregation behaviour of phospholipids in aqueous medium. In particular we review the data showing that phosphatidylcholines (lecithins) form reverse micellar structures in certain apolar solvents. In these systems not only low molecular weight compounds but also catalytically active enzymes and entire cells can be solubilized. In addition, highly viscous phosphatidylcholine gels can be obtained in organic solvents upon solubilizing a critical amount of water. Generally, phospholipid-based reverse micelles can be regarded as thermodynamicall…
Structural Investigation of Water/Lecithin/Cyclohexane Microemulsions by FT-IR Spectroscopy
1995
Abstract FT-IR spectra of water/lecithin/deuterated cyclohexane microemulsions as a function of water/lecithin molar ratio R ( R = [water]/[lecithin]) at various volume fractions ( O ) of the micellar phase have been recorded at 25°C. After elimination of the small spectral contributions due to deuterated cyclohexane and normalization, the shape of the C–H stretching band due to lecithin has been found dependent upon R and O whereas that of the O–H stretching band has been found dependent only upon R . The change in shape of the C–H band was interpreted in terms of a modification of the lecithin alkyl chain packing order. The analysis of the O–H band provides evidence that the hydroxylic gr…
Spectroscopic study of polynucleotides in cationic W/O microemulsions
2007
Water has an active and key role in determining the structure of DNA. Entrapment of DNA and of synthetic model polynucleotides in reverse micelles, where the water activity can easily be modulated, may be a useful way of assessing the influence of water on DNA characteristics; it may also offer useful ideas on the problem of how the giant DNA molecule can be confined in the limited space of cell nuclei. The quaternary microemulsion CTAB n-hexane|n-pentanol| water was used to entrap calf thymus DNA, and the model polynucleotides single-strand polyA, single-strand polyT and duplex polyAT. Ultraviolet spectros-copy, specifically the band at 260 nm, was used to compare the pairing of complement…