A review, with 47 refs. Double emulsions have significant potential in many applications since, at least in theory, they can serve as an entrapping reservoir for active ingredients that can be released by a controlled and sustained transport mechanism. Many of the potential applications are in pharmaceuticals, cosmetics, and food. In practice, double emulsions are thermodynamically unstable systems with a strong tendency for coalescence, flocculation, and creaming. During the last decade much work was carried out to improve the stability and to control the release rates from double emulsions. The review will mention some of the more interesting studies making use of almost any possible combination and blend of monomeric emulsifiers, oils and stabilizers, polymerizable emulsifiers, macromol. surfactants both natural occurring and synthetic, increase viscosity of each of the phases, microspheres and microemulsions in the internal emulsions, etc. The presentation will stress also the most recent achievements in this area including: (i) the use of specially tailor-made polymeric emulsifiers to improve interface coverage and to better anchor into the dispersed phases; (ii) droplet size redn. by forming microemulsions or vesicles in the internal phase; (iii) an improvement in the understanding of the release mechanisms; (iv) the use of different filtration techniques to improve the monodispersibility of the droplets; and (v) use of various additives (carriers, complexing agents) to control the release via the reverse micellar mechanism. [on SciFinder(R)]

Sub-zero temp. DSC measurements were conducted to evaluate the behavior of water in non-ionic microemulsions. Two surfactant systems were studied. The first, based on ethoxylated fatty alc., octaethylene glycol mono n-dodecylether and also contg. water, pentanol and dodecane at a fixed wt. ratio of 1:1. The second system, based on oligomeric ethoxylated siloxanes, water and dodecanol as oil phase. In both systems it was found that in up to 30 wt.% of the total water content, all water mols. solubilize in the amphiphilic phase and are bound to the ethylene oxide (hereafter referred to as EO) head-groups. No free water exists in the surfactant aggregates' core. Up to three mols. of water are bound to each EO group. In the first system, the behavior changes significantly upon adding more water. The added pentanol allows further swelling and the water penetrates into the amphiphile structures and forms a reservoir of free water. Structures are deformed and grow from elongated channels (up to 15-20 wt.% water), via ill-defined (one-dimensional growth) local lamellar structures (up to ca. 60 wt.% water) to spherical normal, O/W micelles (at ≥85 wt.% water). In contrast, the oligomeric systems, due to geometrical restrictions of the amphiphiles and the nature of their curvature that prevents inversion, cannot further solubilize water in the surfactant aggregates' core, causing phase sepn. to occur. [on SciFinder(R)]

Both hydrophobic emulsifiers and submicronial fat particles are needed to stabilize water-in-vegetable oil emulsions. Polyglycerol polyricinoleate (PGPR) is superior to glycerol monooleate and/or lecithin, but is incapable of stabilizing fluid emulsions for sufficient storage periods. Fluid emulsions, unlike margarine, exhibit high droplet mobility and are susceptible to flocculation and coalescence. Submicronial $\alpha$-form crystals of hydrogenated fat can be obtained in the oil phase by the flash-cooling process. The crystals are homogeneously almost mono-dispersed and exhibit insufficient stability against flocculation and phase sepn. The use of an emulsifier (PGPR) in the fat crystn. process was very helpful in decreasing the aggregation and flocculation processes. The $\alpha$-form (mixed with $\beta$'-form) submicronial crystals can stabilize water-in-oil emulsions only in the presence of food emulsifiers, provided the concn. of tristearin is limited to 1.0-2.0 wt% (to prevent phase sepn. and high viscosity) and the PGPR is added at sufficient concns. (PGPR/tristearin ratio of 2.0 or more). Ideally stable (for over 6-8 wk) fluid emulsions can be formed in systems composed of fat submicrocryst. hydrophilic particles and food-grade emulsifiers. These water-in-oil emulsions can serve as the basic prepn. for any food-grade water-in-oil-in-water double emulsion. [on SciFinder(R)]

A review with 58 refs. discusses formation and stability of double emulsions employing polymeric and macromol. surfactants. Controlled release and transport mechanisms are discussed. [on SciFinder(R)]

A review with 75 refs. Research work and progress on several major issues related to double emulsions have taken place recently. Such developments include the intrinsic thermodn. instability derived from the droplets size of the double emulsion; how the release of active ingredients entrapped within the inner phase can be prolonged and controlled; new advanced methods for studying the structure and nature of double emulsion droplets and their interfaces; new possible applications of double emulsions for sustained and prolonged release of active ingredients in cosmetics, food, agriculture and pharmaceuticals; double emulsions as intermediate systems in the prepn. of microspheres or nanospheres; and the scope and limitations of possible new applications of multicompartment microspheres prepd. from double emulsions. [on SciFinder(R)]

A hydrocolloid, extd. from Portulaca Oleracea, comprises the compn. as shown: humidity 10-11%, fat 0. 5-0.6%, proteins 2.5-3.2%, nutritionable water sol. fibers 60-62%, nutritional non water sol. fibers 7.5-8.5% and total nutritional fibers 68-70%. To be more specific, the sugar contents in the fibers are as shown D-galactose: L-arabinose: L-rhamnose: D-xylose: D-galacturonic acid (40: 20: 5: 1: 31); and the compn. of the ash portion is as given with the unity mg/kg: 1400 Ca, 20,000 Mg, 60,000 K; 2,000 Na, 900 Fe, 460 S, 720 P, 60 Al. The mol. wt. of the fraction of the hydrocolloid has a distribution as shown: up to10000 daltons 34%; 10,000-100,000 daltons 12%; 100000-10000000 daltons 33%; 10,000,000-100,000,000 daltons 11%; \textgreater100,000,000 daltons 10%. In addn., the soly. in water, the viscosity, the surface tension and the interface tension of the hydrocolloid have been analyzed. The prepn. of hydrocolloid includes the steps of crushing Portulaca Oleracea in the presence of ethanol in a ratio of 1: 1 (wet plant: ethanol); drying the solid fraction and extg. with acetone; extg. the remainder with a mixt. of toluene: ethanol in a ratio of 1: 2; extg. the remainder with water; centrifuging the aq. fraction in order to remove the rest of the plant; adding ethanol to the aq. fraction in a ratio of ethanol: aq. soln. 3: 1; pptg. hydrocolloid. The prepn. of said emulsion comprises the steps of: dissolving the hydrocolloid in water at room temp. with stirring overnight; dripping the oil into the soln. and stirring in a homogenizer for 5 min for all the oil being dripped into the emulsion; continuing to stir for another 10 min. The hydrocolloid can be used in the following ways: being part of an emulsion; being part of a pharmaceutical prepn. which has effects on reducing the sugar level in the blood and the blood pressure. Further, the pharmaceutical compn. may be an emulsion. However, it may be any suitable tablet, capsule, soln., etc. [on SciFinder(R)]

A system of coating comprises applying a primary coating having a surface energy 22-28 dynes/cm2 of polymeric material having nonstick and hardness properties and applying a top coating having surface energy ∼18-21 dynes/cm2 of a silicon polymer, and in between a bi- or polyfunctional org. compd. to wet the surface of the primary coating and chem. or phys. bond and couple the primary coating and top coating together. The coated substrates are resistant to marking by graffiti, to marine fouling organisms, and adhesion by ice. Steel substrates were coated with a primary coating of epoxy-siloxane emulsion compn., and top coated with poly(di-Me siloxane) contg. Tween 80 coupling agent. [on SciFinder(R)]

The adsorption of diisooctyl sulfosuccinate (AOT) from high ionic strength soln. onto well-defined calcium oxalate monohydrate (COM) and dihydrate (COD) crystals was studied. Adsorption at the COM/soln. interface is characterized by a two-step (LS type) isotherm, starting at low equil. concns. (5 mg dm-3). At ceq = 15-30 mg dm-3 it reaches a plateau which is followed by a relatively steep inflection (ceq = 30-50 mg dm-3) and a further slow increase of the adsorption as a function of increasing AOT concn. In suspensions without surfactant the particles were neg. charged. Upon adsorption an initial slight decrease of the neg. $\zeta$-potential, coinciding with the first plateau, occurred which was followed by a sharp increase in concordance with the increasing surface concn. of the surfactant. In contrast, adsorption onto COD is characterized by a sigmoid isotherm. It commenced at 14 mg dm-3 of AOT and increased abruptly up to a plateau. The max. adsorbed amt. was about half the max. amt. adsorbed on COM, the corresponding adsorption densities in mols. per square nanometer being 7.45 for COD and 14.22 for COM, resp. COD crystals suspended in electrolyte soln. without surfactant were almost uncharged, and the neg. $\zeta$-potential increased in concordance with AOT adsorption. The results are discussed in accordance with literature data and by considering the ionic structure of the different crystal faces. It is assumed that the first adsorption step in the COM/surfactant system is due to electrostatic interactions causing head-on adsorption of the surfactant mols. at high-energy sites, while in the second step a bilayer is formed. In the COD/surfactant system the hydration layers covering the COD crystal faces are shielding them from electrostatic interactions. Consequently AOT adsorption at the COD/soln. interface proceeds only through surface aggregation, resulting in a bilayer of intertwined surfactant mols. [on SciFinder(R)]