Kozo Shinoda

Evaluation of the hydrophile-lipophile balance (HLB) of nonionic surfactants. I. Multisurfactant systems

Since the hydrophile-lipophile property of nonionic surfactant for a given system is just balanced in a three-phase region of a phase diagram which is a stack of three-phase triangles consisting of an aqueous, a surfactant, and an oil phase, we defined the hydrophile-lipophile balance (HLB) plane on which the three-phase triangle is positioned in the midst of the three-phase region. In a three-component system of nonionic surfactant/water/oil, the HLB plane is located at fixed temperature (THLB). Accordingly, the equation of the HLB plane is represented by T = THLB in this system, and, hence, the phase inversion temperature of emulsion (PIT) is independent of a surfactant concentration. Correlation between THLB and the Griffins HLB number was investigated and a linear relationship between them was obtained. In a multisurfactant system, a set of the HLB planes exists in a temperature range between THLB of the most hydrophilic surfactant and that of the most lipophilic surfactant. The equation of the plane is obtained by a geometrical calculation in a space of temperature and compositions, assuming that the equilibrium concentration of surfactant in the aqueous phase is negligible. The effect of the temperature, the oil/water ratio, the weight ratio between the surfactants, and the surfactant concentration on the phase behavior of a mixed surfactant system is explained very well by the equation. The correlation between the THLB of the surfactant mixture and Griffins HLB number is also substantiated.

PHASE BEHAVIOR IN SYSTEMS OF NONIONIC SURFACTANT/ WATER/ OIL AROUND THE HYDROPHILE-LIPOPHILE-BALANCE-TEMPERATURE (HLB-TEMPERATURE)

ABSTRACT The phase diagram of the C12H25(OCH2CH2)5OH/water/tetradecane system was studied around the critical solution temperatures of surfactant-water and surfactant-oil phases. Although the phase behavior is very complicated due to the formation of liquid crystalline phase, basic phase-changes around the three-phase region, consisted of a water, a surfactant and an oil phases, are the same as those in a short-chain nonionic surfactant system.

The interaction between polymer and surfactant: The composition of the complex between polyvinylpyrrolidone and sodium alkyl sulfate as revealed by surface tension, dialysis, and solubilization

Abstract The interaction between polyvinylpyrrolidone (PVP) and sodium alkyl sulfate (RSO 4 Na) in 0.1 N NaCl solution has been studied by surface tension, dialysis equilibrium, and solubilization. Two transition points were clearly found on the surface tension vs. concentration curves of RSO 4 Na in the presence of PVP. The first transition point is considered as the concentration at which the adsorption of RSO 4 Na on PVP begins, and the second transition point is considered as that at which the adsorption of RSO 4 Na on PVP is complete. This reasoning was confirmed from the results of dialysis equilibrium and solubilization. The weight ratio of PVP to sodium dodecyl sulfate (R 42 SO 4 Na) consumed for the complete adsorption was constant, i.e. , 1: 2.3 regardless of the amount of PVP in solution. The concentration of RSO 4 Na above which the adsorption of RSO 4 Na on PVP begins was about 40% lower than the respective critical micelle concentration (CMC). The relationship between the logarithm of the CMCs or of the concentration of RSO 4 Na at first transition points and the hydrocarbon chain length of RSO 4 Na was linear. The slope of the first transition point vs. the hydrocarbon chain length agreed with that of the CMC, that is, the free energy of transferring a CH 2 from aqueous solution to the aggregate (complex) or to the micelle is in both cases 1.1 kT . It can be deduced from these results that RSO 4 Na molecules adsorbed on PVP seem to contact each other and not to be uniformly distributed on the PVP molecules right from the initial stages of adsorption.

Solution behavior of aerosol ot/water/oil system

Abstract The phase diagrams of water-cyclohexane containing 5, 10, and 20 wt% sodium 1,2-bis(2-ethylhexyloxycarbonyl)-1-ethanesulfonate (Aerosol OT, AOT) as a function of temperature were studied. There is the water phase in which AOT is dissolved and a large amount of oil is solubilized at higher temperature, and the oil phase in which AOT is dissolved and a large amount of water is solubilized at lower temperature. It is evident from the phase behavior that the hydrophile-lipophile property of AOT is well balanced. Accordingly, the phase diagram and properties of AOT solution are affected rather sensitively by the addition of a small amount of hydrophilic or lipophilic additive or by temperature. Careful elimination of inorganic salts also influences markedly the solution properties of AOT. Thus, the addition or removal of known amounts of inorganic salts, such as Na2SO4 is also very important to control the solution properties related to practical applications. In this context phase diagrams of both carefully purified and commercial AOT with or without additives have been determined.

Microemulsions and phase equilibria. Mechanism of the formation of so-called microemulsions studied in connection with phase diagram

Abstract The relation between the phase diagrams and the formation of so-called microemulsions (swollen micellar solutions) have been studied. The relation of the amount of oil, water, ionic surfactant, and cosurfactant necessary to obtain transparent one-phase solutions is clearly understood from the phase diagrams. The changes of interfacial tension in hydrocarbon-water systems containing ionic surfactants as a function of added pentanol or octylamine were also studied in connection with phase diagrams. The interfacial tension is very small, and solubilization is maximal when the mixing ratio of ionic (hydrophilic) surfactant and (lipophilic) cosurfactant is optimum.

EVALUATION OF EMULSIFIER BLENDING

ABSTRACT The mechanism of emulsifier blending of different hydrophile-lipophile balance has been studied by the measurements of 1) the phase inversion temperature ( PIT) in emulsions, 2) the size distribution of droplets and the stability of emulsions, and 3) the cloud points of aqueous solutions. The PIT was slowly depressed with the replacement of lipophilic emulsifier at first and then suddenly and discontinuously dropped when the difference in HLB of two emulsifiers is too large. These results imply 1) the HLB number of emulsifier blend markedly deviates from weight average of two emulsifiers and 2) the PIT of certain temperature range, i. e., HLB of certain range cannot be prepared by blending, provided the difference in HLB (or PIT) of two emulsifiers is too large. The emulsion droplets were smaller and the emulsion was more stable when the difference of HLB of emulsifiers to be blended is smaller in the mixture of Tween and Span type emulsifiers. There was, however, an optimum difference in HLB in ...

Some observations on phase diagrams and structure in binary and ternary systems of sodium and calcium dodecyl(monooxyethylene) sulfate

Abstract The phase equilibria of sodium (SDE 1 S) and calcium (CDE 1 S) dodecylmonooxyethylene sulfate in two- and three-component systems are studied by water deuteron NMR and polarizing microscopy methods. In the binary systems with water both SDE 1 S and CDE 1 S give micellar solutions, followed by the normal hexagonal liquid crystalline phases at 293 K. At high temperatures and with low water content, the lamellar liquid crystalline phases are also formed. The micellar aggregates with Ca 2+ as counterion start to grow at very low concentration whereas with Na + counterion, the micellar growth is observed only at very high surfactant concentration. The micellar solution and hexagonal liquid crystalline phases solubilize very small amounts of decanol which also increases the stability of the liquid crystalline phases toward the water corner. In the ternary system at 293 K, the coexistence of two lamellar liquid crystalline phases, one at high water content and the other at low water content, is detected with Ca 2+ as counterion whereas with Na + ion, there exists only one lamellar liquid crystalline phase with an extensive stability range. The lyotropic nematic liquid crystalline phases are found to form in the ternary systems with high water and very low decanol contents, and the structure of the phases are of lamellar-nematic type with Na + and hexagonal-nematic type with Ca 2+ as counterion. The calcium system also yields reverse hexagonal liquid crystalline phase with high both surfactant and decanol contents. The micellar growth and the coexistence of two lamellar liquid crystalline phases are explained qualitatively by recent theoretical models of attractive double-layer forces and image-charge interactions.

Characteristic properties of lecithin as a surfactant

Abstract Characteristic solution properties of lecithin were studied in 1) water+propanol/lecithin/hexadecane and 2) ethanol/lecithin/ hexadecane systems. 1) Solvent property of water changes by added alcohol and the hydrophile-lipophile property of lecithin is balanced in 13 wt% propanol aq.-hexadecane system. Three liquid phases, i.e. aqueous alcohol, lecithin and hexadecane are found. The volume fraction of the lecithin phase increases with its concentration and at 2.3 wt%/system, all solvent molecules are swelled and one microemulsion phase is obtained. 2) In ethanol/ lecithin/hexadecane system, lecithin is also insoluble in the solvent, and swells a large amount of hexadecane.

Similarity in phase diagrams between ionic and nonionic surfactant solutions at constant temperature

The nonionic surfactants of the polyoxyethylene alkyl (aryl) ether type show hydrophilic properties at low temperatures and gradually change to lipophilic properties at high temperatures. The reason for this is found in a reduced interaction between the hydrophilic moiety of nonionic surfactant and water with increased temperature. This means that the hydrophile-lipophile properties of nonionic surfactants will be balanced at a certain temperature for a given system. Above this temperature the surfactant is oleophilic and soluble in the given oil and below it hydrophilic and mainly soluble in water. Emulsion type changes from an O/W to a W/O type at this temperature. The temperature is called phase inversion temperature (PIT) in emulsion of HLB temperature, because the hydrophile-lipophile balance (HBL) of a nonionic surfactant in the given system just balances at this temperature. The solubilization of oil (or water) in aqueous (or nonaqueous) surfactant solution is large close to the PIT.

Solubilization of cyclohexane in aqueous solutions of sodium a-alkyl alkanoates

The effect of branched alkyl chain length and the position of the COONa group on the solubilizing power of n-alkane sodium carboxylates was studied. The lipophilic property and the amount of solubilized cyclohexane increased with the branched chain length of branched soaps, and with the change of the position of the -COONa group from 3 to 7 in the alkyl chain of pentadecane -3, -5, and -7 sodium carboxylates. Alpha-branched soaps having proper branched alkyl chains were better solubilizers for cyclohexane than straight chain compounds. The amount of cyclohexane solublized by C/sub 10/ H/sub 21/ CH(C/sub 6/H/sub 13/) COONa was about three times greater than the amount solubilized by C/sub 17/ H/sub 35/ COONa. There was a marked increase in the solubilization of cyclohexane replacing ..cap alpha..-branched fatty acid soaps with optimum amount of cosurfactants such as C/sub 8/H/sub 17/ (OCH/sub 2/CH/sub 2/)/sub 2/OH. Namely, solubilization increased markedly at the optimum hydrophile-lipophile balance of mixed surfactant. 21 references.