Peer Review Publications

Nanoparticles (1-6 nm) of transition metals (e.g., Pt, Pd), alloys, metal oxides (e.g., FeOOH, SiO2), and ceramics are prepd. by chem. reaction under mild conditions using precursor solns. of complex liqs. (e.g., microemulsions, liq. crystals) contg. surfactants and alkoxides. The resulting nanoparticles are dispersed in polymer solns. as fine colloids, and used to form transparent nanoparticle-contg. plastic films. The water is non freezing, the mild conditions are atm. pressure and a temp. range of room temp. to 70°C, and the reaction is selected among a hydrolysis, redn. and exchange process. In an example, a Pd colloidal dispersion was prepd. from a soln. contg. K2PdCl4, Aliquat 336, dichloroethane and water, which was reacted with NaHCO2 under Ar at 75°C for 1 h. The solvent was evapd. off, leaving a waxy residue which was washed and dried. The Pd nanoparticles were redispersed in polyvinylalc., and used for forming a transparent film coating on a glass plate. [on SciFinder(R)]
Nissim Garti and Martin E Leser. 1999. “Natural hydrocolloids as food emulsifiers.” Annual Surfactants Review, 2, Design and Selection of Performance Surfactants, Pp. 104–145. Abstract
A review with 83 refs. is given. Research activities carried out on various gums as emulsifiers are discussed and questions related to adsorption at interfaces of certain gums are clarified. Gum arabic, galactomannans (guar, locust bean, and fenugreek gum), xanthan gum, Portulaca oleracea and Opitus ficus gums, tragacanth gum, and pectins are included. Adsorption isotherms and the role of proteins in galactomannans, mechanistic considerations, protein-polysaccharide interactions, the stabilization by solid particles (colloidal microcryst. cellulose as emulsifier), and biosurfactants are discussed. [on SciFinder(R)]
Helga F Milhofer, Nissim Garti, and Alexey. Kamishny. 1999. “Process for preparation of novel aspartame crystals.”. Abstract
New crystal forms of aspartame were prepd. by using microemulsions comprising: (a) introducing aspartame into a microemulsion formed from an oil phase, an aq. phase and at least one emulsifier; (b) destabilizing the microemulsion to effect recrystn. of aspartame; (c) sepg. solid phase crystals from the liq. phase in which they are contained; and (d) cleaning the crystals to remove traces of the oil phase and surfactant. Thus, aspartame (22 g) was solubilized by mech. stirring in a microemulsion contg. 234 g (65%) of isooctane, 36 g (10%) of water and 90 g (25%) AOT at 65°. The microemulsion was then cooled at a rate of 1° per min with const. sirring to a final temp. of 5° and stirred at this temp. for an addnl. two hours to induce crystn. The crystal gave an X-ray pattern characteristic of form III aspartame. [on SciFinder(R)]
Shlomo Magdassi and Nissim. Garti. 1999. “Multiple emulsions.” Cosmetic Science and Technology Series, 19, Novel Cosmetic Delivery Systems, Pp. 145–167. Abstract
A review with 66 refs. Prepn. of multiple emulsions, evaluation of yield of prepn. and formulations are discussed. [on SciFinder(R)]
A Yaghmur, A Aserin, Y Mizrahi, A Nerd, and N Garti. 1999. “Argan oil-in-water emulsions: preparation and stabilization.” Journal of the American Oil Chemists' Society, 76, 1, Pp. 15–18. Abstract
We prepd. stable oil-in-water emulsions of argan oil with two different types of mixts. of nonionic emulsifiers. Three different types of oil (Israeli argon oil, Moroccan argan oil, and soybean oil) were emulsified with mixts. of Span 80 and Tween 80. The optimum HLB value for argan oil was 11.0 (±1.0). The argan oil-in-water emulsions were stable for more than 5 mo at 25°C. Synergistic effects were found in enhancing stability of emulsions prepd. with sucrose monostearate. The origin of the oil and the internal content of natural emulsifiers, such as monoglycerides and phospholipids, have a profound influence on its interfacial properties and on the stability of the argan oil-in-water emulsions. [on SciFinder(R)]
Abraham Aserin, Nissim Garti, and Arnon. Shani. 1998. “Lubricous coating compositions containing jojoba oil.”. Abstract
Coating compns. comprise natural or synthetic jojoba oil which is optionally partially or completely hydrogenated and/or isomerized, a solvent, or a dispersing system (an immiscible org. liq. and dispersing agent). The coating compns. are for polymers or plastics or naturally occurring macromols. with high hydrophobicity or with low or medium surface energy. Thus, a coating contained GKF 8-10 (octane-decane) 46.5%, pentane-hexane 46.5%, jojoba oil 5.8%, glycerol 0.5, and fragrances 0.7%. [on SciFinder(R)]
S Ezrahi, A Aserin, and N Garti. 1998. “An excursion into phase tetrahedra-where physical chemistry and geometry meet.” Journal of Chemical Education, 75, 12, Pp. 1648–1652. Abstract
The authors have shown how triangles and tetrahedra can be used to represent the compn. and phase behavior of three- and four-component systems. The relationship between such triangular representations and the full tetrahedron is explained by geometric considerations of the cross-sections through the tetrahedron. [on SciFinder(R)]
S Ezrahi, A Aserin, and N Garti. 1998. “Structural evolution along water dilution lines in nonionic systems.” Journal of Colloid and Interface Science, 203, 1, Pp. 222–224. Abstract
The authors studied the nonionic system water/dodecane/butanol/ polyoxyethylene (10) oleyl alc., and water/dodecane/pentanol/ polyoxyethylene (8) lauryl alc. A pronounced increase in cond. may be the result of a microstructural change, not an inversion from W/O to O/W. Microstructural evolutions of two model systems along two different diln. lines, where the wt. ratios of surfactant/alc./oil are 2:1:1 and 4:3:3, resp., are similar. The inversion from W/O to O/W microemulsion should occur at a water content much higher than 20-30 wt%. (c) 1998 Academic Press. [on SciFinder(R)]
VD Fedotov, Natalija N Vylegzhanina, AE Altshuler, VI Shlenkin, Yu. F Zuev, and N Garti. 1998. “An electron spin resonance study of the soy bean phosphatidylcholine-based reversed micelles.” Applied Magnetic Resonance, 14, 4, Pp. 497–512. Abstract
The ESR spectra of 1-palmitoyl-2-stearoyl-(n-doxyl)-glycero-3-phosphocholine spin label positional isomers (n = 5, 7, 10, 12 and 16) were studied in soy bean phosphatidylcholine (SPC)-based microemulsions with various vol. fractions of disperse phase over the wide temp. range. The max. hyperfine splitting 2Amax and the order parameters S were taken as indexes of the rotational mobility and the motion spatial restrictions of the labeled lipid chain segments. The temps. Ttr at which sharp enhancements of 2Amax and S occur depend on concn. and size of the reversed micelles in solns. To explain this, a plausible model, taking into account capability of the SPC mol. hydrocarbon chains to change a tilt angle with respect to the surface of a polar head group as temp. varies, is proposed. The estns. of the correlation times $\tau$sl obtained from the lineshape characteristics of the ESR spectra provided the possibility to suggest that these correlation times characterize the reorientations of the SPC chain axis about the normal to the surface of a polar head group of a reversed micelle. [on SciFinder(R)]
N Garti. 1998. “New trends in double emulsions for controlled release.” Progress in Colloid & Polymer Science, 108, Pp. 83–92. Abstract
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)]
A review, with 38 refs. Double emulsions are emulsion-within-emulsion systems with promising applications. Attempts were made to find new amphiphiles to improve their thermodn. stability and to control the release of active matter or markers from double emulsions. The efforts to study the mechanisms of stabilization and release of water-sol. markers from W/O/W double emulsions are summarized, and the achievements in designing an ultimate synthetic graft-comb copolymeric amphiphile for the internal water-oil interface (the W/O emulsion) as well as for the external oil-water interface (the O/W emulsion) are presented. The amphiphilic polymers allow formation of small multicompartment emulsion droplets of W/O/W that are shear (homogenization) and mech. (centrifugation) resistant. The interface is covered with thick emulsifier layers that impart long-term stability. Addn. of controlled amts. of monomeric emulsifiers (Spans) will form reverse micelles in the oil phase, which are capable of transporting the markers via a diffusion-controlled mechanism from the inner to the outer interface. The tailor-made polymers are an excellent soln. to the 2 key problems that, so far, have prevented the use of double emulsions in certain industrial applications: stability and release. Agricultural formulations, based on stabilization by these polymers, have shown considerable advantages over other common techniques of encapsulating or entrapping active matter. [on SciFinder(R)]
N Garti, A Aserin, I Tiunova, and S Ezrahi. 1998. “Sub-zero temperature behavior of water in non-ionic microemulsions.” Journal of Thermal Analysis and Calorimetry, 51, 1, Pp. 63–78. Abstract
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)]
N Garti, H Binyamin, and A Aserin. 1998. “Stabilization of water-in-oil emulsions by submicrocrystalline à-form fat particles.” Journal of the American Oil Chemists' Society, 75, 12, Pp. 1825–1831. Abstract
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)]
Nissim. Garti. 1998. “Preface.” Journal of Thermal Analysis and Calorimetry, 51, 1, Pp. 7–8.