Recent NMR studies on aqueous solutions of surfactants are reviewed. It is demonstrated that measurements of 13C and 2H NMR multifield relaxations and pulsed gradient FT-NMR are useful to investigate molecular dynamics of surfactant aggregates such as micelles. 17O NMR studies on hydration of micelles are also described.
Calorimetric studies have been applied for the solutions of (amphiphiles + r·H2O + hydrocarbons) to investigate the aggregation process of polyoxyethylene glycol monodecyl ether (C10En) and Aerosol OT (AOT) in nonaqueous media. From the heat capacity measurements the shifting processes in the equilibrium between monomeric solutes and aggregates which occur with increasing molality of amphiphiles were detected. From the measurements of enthalpy of dilution the stabilization due to the formation of aggregates were observed. The aggregation process of C10En depends on the length of oxyethylene and also on the solvents. On the other hand, AOT forms only small size of aggregates and the interaction energy of which is very small in cyclohexane. However, by adding small amount of water to those amphiphiles swollen micelles are formed, and passing through a critical molality microemultion is formed. Thermal properties and the aggregation process of amphiphiles which depends strongly on solvents and the addition of water are described.
Micellization of fluorocarbon and hydrocarbon surfactant mixtures in aqueous solution is reviewed. Simple fluorocarbon surfactant micelles can be characterized by growth from sphere to rod-and disk-like form, which is explained by packing constraint. Non-ideality of the mixed systems with head groups of same charge is summarized using interaction parameter calculated by Shinoda's equation. Examples of mixing of separate micelles in the concentrated solutions are given. The mixed systems with different head groups are described from the stand point of micellar growth and vesicle forming.
This review was introduced on the recent studies of thermodynamic arguments for equilibrium penetration. Two penetration systems, especially, which were composed of L-α, β-dimyristoyllecithinN-dodecyl-β-alanine (NDA) surfactant and α, α'-dilaurin NDA were described in detail. The characteristics in investigation of these systems was that adsorbed amount of surfactant was directly measured by a radiotracer technique using tritium-labeled compounds at solution surface with and without the spread monolayers. The molecular complex formation of lecithin and NDA was precisely explained how to be analyzed from the enthalpy changes of spread films and adsorbed surfactant in penetration at water surface.
Iridescent aqueous solutions of three types of surfactant have been studied. They are anionic alkenylsuccinic acid (ASA), cationic dimethyldioctadecylammonium chloride (DOAC), and nonionic dodecyl glyceryl itaconate (DGI) with small amount of ionic surface active substances. The structure of iridescent ASA solutions has been studied mainly by UV and X-ray diffraction techniques. The results indicate that the iridescent solutions of ASA consist of a lamellar liquid crystal having the spacing distance of submicrometer and the iridescent color appears by the interference of reflected light by single bilayer membranes. The drastic blue-shift in reflection spectra of DOAC can be observed when the iridescent liquid crystal transforms into the gel phase on cooling. The iridescent structure of polymerizable surfactant, DGI, can be immobilized inside the hydro-gel by copolymerization with acrylamide and N, N'-methylenebis (acrylamide).
Recent progress in emulsions and emulsion technology used in many fields is summarized. This paper deals mainly with definition, properties of microemulsion and macroemulsion, their applications in cosmetic, medical, and food fields, preparation of middle phase microemulsions, preparation and properties of multiple emulsions, zeta-potential of microemulsions, emulsionliquid membranes, and flotation separation of O/W type microemulsion.
The autoxidation of certain polyunsaturated triglycerides (PUFA-TG) such as fish oils was inhibited effectively by the addition of 5 % soybean phospholipids (PL) to PUFA-TG used as a substrate. The antioxidative effect of PL became greater with increase in phosphatidylcholine (PC) content in PL. The antioxidative effect of mixed tocopherol (Toc) also increased synergistically by adding 0.1 % Toc and 1 % PL to the substrate. The effects of each phospholipid class such as PC, phosphatidylethanolamine (PE) and phosphatidic acid (PA) were assessed, PC had antioxidative effect and PE, synergistic effect on Toc and PC, PA showed no effect on the autoxidation of PUFA-TG. The strongest antioxidative effect of PC and PE mixture was observed for PUFA-TG when PC was mixed with PE at a ratio of 20 : 1. Remarkable synergistic effects on Toc were observed at ratios of 4 : 1, 2 : 1 and 0 : 1 of PC and PE mixtures. Based on the present results, antioxidative behavior of PL would appear due to the nitrogen containing moiety and not to the phosphoric acid moiety of the PL structure.
Molecular interactions between dipalmitoylphosphatidylcholine (DPPC) and long polyoxylated nonionic surfactants in a lipid bilayer were investigated by dynamic light scattering, ultracentrifuge, differential scanning calorimetry (DSC), ζ-pontential and fluorescence. Particle size and encapsulation efficiency of the liposomes decreased rapidly with increasing concentrations of the nonionic surfactants possessing a long oxyethylene chain (C16POE20, and C16POE40), but showed virtually no change in the case of a short chain C16POE10. The cooperative effect on the physical properties of bilayer caused by interaction among DPPC molecules decreased with increasing concentration of the nonionic surfactants. Surface charge density of the liposomes also decreased following the addition of nonionic surfactants. Microviscosity of the liposome decreased with increasing concentrations of C16POE20 and C16POE40, but remained essentially unchanged in the case of C16POE10. The addition of a long polyoxylated nonionic surfactant to a solution containing DPPC molecules caused structural change of molecular aggregation and in particular, in the presence of large amounts of C16POE20 and C16POE40, the DPPC liposome with nonionic surfactants did not form. A molecular aggregate such as a micelle was obtained instead.
Mixed vesicles including phosphatidylcholine (PC), phosphatidyl serine (PS) and amphoteric crown ether compound (C18-crown-6) with different component fractions were prepared and their ion-complexing phenomena examined by measuring their electrophoretic mobilities in different salt solutions. The crown ether compounds retained their selectively ion-complexing ability for some special cations (K+ and Ba2+) even on the vesicle surfaces. The zeta-potentials of the mixed vesicles of PC+PS+crown were determined extensively by fraction of the PS component and variation in metal cations in aqueous solution. That is, this parameter shifted remarkably in a negative direction with increase in the PS-fraction only in salt solutions containing K+ or Ba2+. No shifting of zeta-potentials could be detected in the case of (i) PC+PS vesicles without crown ether or, (ii) salt solutions that did not complex with the crown ether (Li+ or Ca2+).
Leftover meals, have been used to make feed for domestic animals. This report describes fried garbage manufacturing with fat under reduced pressure and repeated runs. The level of saturated and mono-unsaturated fatty acid increased with usage, while polyunsaturated fatty acid level decreased. As for fatty acids of fried meal fat, this was not observed but under storage at 37°C, it was. The determination of chemical components, mineral and PCB of raw or fried garbage was conducted. A comparison with other data, indicated fried ones have as high qualities as the other guaranteed feeds for animals. Two meals were made for sea bream aquaculture. One was made of soluble fish, fish meal, dried Tofu cake (bean curd lees), wheat meal, crab-processing waste, corn meal and fish oil. The other one was made from dried garbage, crab shells, wheat meal, corn meal and crab-processing waste. These meals were examined for preservation with or without antioxidant. Preservative conditions were day-light irradiation, fixed 40°C (dark), cold-storage (-20°C, dark) for 20, 40, and 60 d. Acid, peroxide and fatty acid profile and carotenoidal coloring matters were determined. Under conditions of day-light irradiation or of a temperature of 40°C, feed containing garbage without antioxidant showed inferior fat quality (POV; 26.1 79. 7, 26. 1→ 42.3), but with antioxidant, improvement was noted (POV : 26. 1→ 30.1).
The unique rheological property, rheopexy, of O/W emulsions stabilized with fatty alcohol was investigated. A cone-and-plate viscometer, differential scanning calorimeter (DSC) and optical microscope were used to characterize the O/W emulsions. Flow curves of each emulsion sample were obtained using a cone-and-plate viscometer. Flow hysteresis curves for the emulsions could be distinguished on the basis of the four following patterns : (1) no hysteresis, (2) rheopexy, (3) mixed patterns of rheopexy and thixotropy, and (4) thixotropy. The flow curve of each emulsion showed transition from pattern (1) to (4) with increase in the fatty alcohol/surface active agent ratio.