Microstructure Of Microemulsion Research Articles

Phase equilibria and microemulsion structure for a triple-chained soap: Sodium di-2-butyldecanoate

An alkyl carboxylate with a very voluminous hydrophobic part, sodium di-2-butyldecanoate, was prepared and its phase behavior investigated in mixtures with water (25–100°C) and in mixtures with both water and decane (25°C). Furthermore, the homogeneous phases formed were characterized on the basis of NMR and self-diffusion studies. In the two-component water-surfactant system there is an extensive lamellar liquid crystalline phase region as well as two isotropic solution regions, one at lower and one at higher surfactant concentrations than the lamellar liquid crystalline region. The latter solution phase has unusual features in respect to location in the phase diagram, solution structure, and the formation of metastable lamellar phase, transforming slowly into isotropic solution. Sodium di-2-butyldecanoate can mix equal amounts of water and hydrocarbon into homogeneous solution and the water-to-hydrocarbon ratio of the microemulsions can be varied over very large ranges. Depending on composition, the microemulsion microstructure is of the water droplet-in-oil type or bicontinuous.

Microstructure of microemulsions by freeze fracture electron microscopy

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMicrostructure of microemulsions by freeze fracture electron microscopyW. Jahn and R. StreyCite this: J. Phys. Chem. 1988, 92, 8, 2294–2301Publication Date (Print):April 1, 1988Publication History Published online1 May 2002Published inissue 1 April 1988https://doi.org/10.1021/j100319a039RIGHTS & PERMISSIONSArticle Views1307Altmetric-Citations274LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (4 MB) Get e-Alerts

Microstructure of formamide microemulsions from NMR self-diffusion measurements

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMicrostructure of formamide microemulsions from NMR self-diffusion measurementsK. P. Das, A. Ceglie, and B. LindmanCite this: J. Phys. Chem. 1987, 91, 11, 2938–2946Publication Date (Print):May 1, 1987Publication History Published online1 May 2002Published inissue 1 May 1987https://doi.org/10.1021/j100295a058RIGHTS & PERMISSIONSArticle Views252Altmetric-Citations54LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts

Gaussian curvature in an Ising model of microemulsions

We extend Widom’s Ising-like model of microemulsions on a simple cubic lattice by a new term which accounts for the Gaussian curvature energy of the oil–water interfaces. The new term distinguishes between different topologies of the interfaces and plays an important role in determining the microstructure of microemulsions on a scale larger or comparable to the persistence length provided that the microemulsion is dominated at all by curvature energies. We also speculate on its possible role for the breakdown of curvature energies in microemulsions.

Interfacial tensions and phase behavior of alcohol-hydrocarbon-water-sodium chloride systems

The phase behavior and interfacial tensions of mixtures of alcohol, alkane, water, and sodium chloride that split into two or three liquid phases at 25/sup 0/C are reported as a function of type of alcohol and alkane and sodium chloride concentration. The patterns of phase and tension behavior are similar to those observed with surfactant-based microemulsion systems but in a higher tension regime. The qualitative patterns of phase and tension behavior in the alcohol systems appear to be characteristic of all amphiphile-oil-brine systems, although the magnitudes of the interfacial tensions of microemulsion against oil-rich or water-rich phases can be some hundredfold smaller than the corresponding tensions of the alcohol-rich phase against oil-rich or water-rich phases. This difference appears to be a distinguishing feature of microemulsions and presumably arises from the relatively large scale of microemulsion microstructure. Microemulsions in multiphase equilibria incorporate tenfold or more water or oil than do corresponding alcohol solutions, and this argues for the topology and persistence of that microstructure.

Microemulsion structure in four-component systems for different surfactants

The microstructure of four-component microemulsions composed of ionic surfactant, cosurfactant hydrocarbon and water was studied as a function of surfactant polar head group and alkyl chain length using the multi-component self-diffusion approach, the self-diffusion coefficients being measured by the Fourier transform pulsed-gradient spin-echo 1H-NMR technique. The study concerned both cationic and anionic surfactants and was performed for two cosurfactants, i.e. pentanol and octanol, and a number of hydrocarbons (aliphatic and aromatic). The results obtained demonstrate that in every case the structure is very strongly influenced by the chain length of the alcohol, a longer cosurfactant favouring a droplet-type structure and a shorter one a bicontinuous structure; this occurs irrespectively of the chemical structure of the surfactant and the nature of the oil used. The main effect of the hydrocarbon and surfactant chain lenghts is to influence the distribution of molecules between different domains. The hydrocarbon chain length determines the distribution of oil and alcohol between the medium and the surfactant layers through a competition process that is not affected by the surfactant chemical structure. Furthermore, in a water-in-oil droplet situation, in addition to the larger degree of penetration for shorter alkanes between the surfactant molecules in comparison with the corresponding bicontinuous situation, we have an increased interfacial location of the alcohol with an increase of the surfactant tail length.

Microstructure of microemulsions of the system water-n-tetradecane-alkyl polyglycol ether (C12E5)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMicrostructure of microemulsions of the system water-n-tetradecane-alkyl polyglycol ether (C12E5)F. Lichterfeld, T. Schmeling, and R. StreyCite this: J. Phys. Chem. 1986, 90, 22, 5762–5766Publication Date (Print):October 1, 1986Publication History Published online1 May 2002Published inissue 1 October 1986https://doi.org/10.1021/j100280a058RIGHTS & PERMISSIONSArticle Views416Altmetric-Citations113LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts

Viscoelasticity and microstructure of non-ionic microemulsions

Non-ionic microemulsions were investigated by viscoelastic measurements in the kHz region. We found that in some parts of the phase diagram our systems consisted of a dispersion of spherical oil doplets, stabilized by a non-ionic surfactant, in a continuous phase of almost pure water. Because of the simplicity of the system used it was relatively easy to interpret our measurements in terms of two rheological models developed by Oldroyd. Using these models, we could calculate the interfacial tension between the continuous and the dispersed phase. In other parts of the phase diagram, however, our results indicate the presence of a fluctuating network of oil-swollen cylindrical micelles.

Formation of a middle-phase from a lower or upper-phase microemulsion

The equilibrium theory of lower- and upper-phase microemulsions earlier derived is extended to obtain the conditions for the stability of such microemulsions. Consideration of stability is aimed at understanding how lower- and upper-phse microemulsions separate into a middle-phase and an excess phase, and what are the requirements for the compatibility between a lower-phase microemulsion and a polymer added to it. Under the assumption that the microstructure of microemulsion remains as spherical drops of constant radius, the lower- and upper-phase microemulsions are shown to become unstable and separate into a “middle-phase” and an “excess” phase, as the optimal salinity is approached from either a low or a high salinity. This happens due to the increase in the van der Waals attraction among the drops. The presence of polymer is shown to enhance the phase separation, when the steric repulsion between the microemulsion drops and polymer molecules occurs.

Toward understanding microemulsion microstructure. II

Many equilibrium microemulsion phases can solubilize hydrocarbon and water in all proportions in a continuous progression of states without any visibly abrupt transition. At the extremes are solutions of swollen micelles and swollen inverted micelles. Contending pictures of the midprogression microstructures are (1) crowded swollen micelles and crowded swollen inverted micelles, which cannot coexist alone, and (2) bicontinuous structures, parts of which can be micellar. Which is correct? The most extensive published evidence is electrical conductivity, small-angle x-ray scattering (SAXS), and viscosity data on microemulsions made in our laboratory with an alkylaryl sulfonate mixture that is a commercial type of surfactant. We report here complementary data with a comparable pure surfactant and analyze at length the SAXS evidence. We note that the pure surfactant appears to narrow the ranges over which swollen disjoint interacting micelles exist. We conclude that the continuous progression through buildup and breakdown of bicontinuous structures more readily explains all of our data and a number of findings by other investigators.

Toward understanding microemulsion microstructure: A small-angle x-ray scattering study

The microemulsion phases formed in solutions of octane, commercial surfactant, and alcohol with various brines are examined with small-angle x-ray scattering (SAXS), electrical conductivity, and viscosity techniques. Models based on monodisperse populations of swollen micelles or microemulsion ‘‘droplets’’ adequately represent the SAXS data at low volume fractions of brine. Introduction of hard-sphere interactions with the Percus–Yevick approximation allows us to model the composition dependence of the radius of gyration and isothermal compressibility up to volume fractions of brine near a percolation threshold for electrical conductivity. For brine volume fractions above the percolation threshold, a mean field attractive interaction term is needed to model the variation of isothermal compressibility; however, the same theory fails to model the composition dependence of the apparent radius of gyration. But predictions from a model for a bicontinuous microemulsion structure that is geometrically irregular yet topologically ordered and that evolves continuously into swollen (inverted) micellar solutions at low volume fraction of water (oil) are in good agreement with the SAXS and electrical conductivity data over a wide range of brine volume fractions.