| 1. |
- Alander, J, et al.
(författare)
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Model microemulsions containing vegetable oils Part 1: Nonionic surfactant systems
- 1989
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Ingår i: Journal of the American Oil Chemists Society. - 0003-021X .- 1558-9331. ; 66, s. 1656-1660
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Tidskriftsartikel (refereegranskat)abstract
- Nonionic microemulsions containing triglucerides and fatty acid esters as lipophilic components have been studied. The phase inversion temperature (PIT) of the systems was determined by a conductometric method. Partial phase diagrams were constructed in the phase inversion temperature range. Water solubilization capacity of the nonionic surfactant systems studied was dependent on surfactant and oil types in analogy to ordinary hydrocarbon systems. The PIT:s increased with increased molecular weight for both esters and triglycerides.
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| 2. |
- Alander, J, et al.
(författare)
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Model microemulsions containing vegetable oils Part 2: Ionic surfactant systems
- 1989
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Ingår i: Journal of the American Oil Chemists Society. - 0003-021X .- 1558-9331. ; 66, s. 1661-1665
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Tidskriftsartikel (refereegranskat)abstract
- The phase behavior and the structure of ionic microemulsions, stabilized by sodium oleate and different alcohol cosurfactants, containing fatty acid esters or triglycerides as lipophilic components, have been investigated. Microemulsions containing triglycerides display a smaller stability region than microemulsions containing hydrocarbons or fatty acid esters. From structural investigations, using the NMR FT pulsed gradient spin echo method for measuring self-diffusion coefficients, differences in the microstructure are revealed as well. Adding an ester (or a hydrocarbon) to a microemulsion containing sodium oleate/pentanol will at certain compositions lead to a gradual transition from a bicontinuous to an oilcontinuous system, while this behavior cannot be detected when adding a triglyceride. Instead, a phase-separation occurs, and it is suggested that the larger molecular size of the triglyceride is responsible for the diffirence.
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| 3. |
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| 4. |
- Backlund, S, et al.
(författare)
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Partial phase behavior of ionic microemulsions stabilized by sodium dodecylsulfate and alcohol cosurfactants
- 1992
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 88, s. 36-41
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Tidskriftsartikel (refereegranskat)abstract
- Ionic microemulsions, stabilized by sodium dodecylsulfate and alcohol cosurfactants, have been characterized with respect to phase behavior, particularly the composition of the different phases in Winsor type I, II and III systems. The system containing brine, octane, sodium dodecylsulfate and 1-butanol shows a regular phase behavior, in conformity with the anticipated behavior, i.e., 2-3-2 phases. The phase transitions with increasing 1-butanol concentration are analogous to those occurring with increasing salinity, when compared with previous investigations. For the system containing brine, cyclohexane, sodium dodecylsulfate and benzyl alcohol, the behavior becomes more complex, even at low surfactant contents. The transitions are 2-3-2-3-2 phases over a wide composition range. The compositions of the phases at equilibrium are discussed in relation to structural considerations, as determined by conductivity and NMR self-diffusion measurements.
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| 5. |
- Backlund, S, et al.
(författare)
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Partical phase equilibria and partition of alcohol cosurfactants in ionic microemulsions
- 1990
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 82, s. 290-295
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Tidskriftsartikel (refereegranskat)abstract
- The partial phase behaviour of quintinary microemulsions containing water (0.5 m NaCl), sodium dodecylfate, octane and alcohol, where the alcohol is a butanol or pentanol isomer, has been determined. In addition, the partition of the cosurfactant between the phases has been investigated, as well as in detail for the 1-butanol system. The efficiency of the cosurfactant for forming microemulsions is found to exhibit no simple relationship to its solubility properties. In addition, while branched alcohol cosurfactants promote the formation of solution phases at high surfactant contents.
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| 6. |
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| 7. |
- Blomberg, E, et al.
(författare)
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Surface interactions in emulsion and liposome solutions
- 1999
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Ingår i: Colloids and Surfaces A. - 0927-7757 .- 1873-4359. ; 159, s. 149-157
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Tidskriftsartikel (refereegranskat)abstract
- We have used two surface force techniques to investigate the interactions between hydrophilic and negatively charged mica and glass surfaces across concentrated and dilute oil-in-water emulsions, as well as across aqueous liposome solutions. It was observed with both the interferometric surface force apparatus, using mica surfaces, and with the non-interferometric MASIF technique, employing glass surfaces, that emulsion droplets adsorbed onto the surfaces. Under a high compressive force the adsorbed emulsion droplets were disintegrated and this resulted in a phase separation in the gap between the surfaces. The forces measured in the presence of the capillary condensate compared favourably with theoretical expectations. In contrast, no adsorption of large aggregates could be detected in the liposome solution. Instead it appears that upon adsorption the liposomes disintegrate and the surfaces become covered by a disordered layer of phospholipids. Measurements with the interferometric surface force apparatus, that allows absolute distances to be determined, allow us to draw the conclusion that some bilayer aggregates are adsorbed and that the inner layer consists of an intercalated monolayer.
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| 8. |
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| 9. |
- Friberg, SE, et al.
(författare)
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Hydrotropes – performance chemicals
- 2004
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Ingår i: Journal of Dispersion Science and Technology. - 0193-2691 .- 1532-2351. ; 25, s. 243-251
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Tidskriftsartikel (refereegranskat)abstract
- The action of hydrotropes is reviewed emphasizing their influence in the formation of microemulsions, vesicle solutions and other products involving surfactant association structures. It is demonstrated that the hydrotropes, the association structures of which, realistically, can only be described as trivial, actually, are powerful and sophisticated performance chemicals playing an essential role in complex applied formulations utilizing more composite amphiphilic association structures
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| 10. |
- Jonströmer, M, et al.
(författare)
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Aggregation and solvent interaction in nonionic surfactant systems with formamide
- 1990
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Ingår i: Journal of Physical Chemistry A. - 1089-5639 .- 1520-5215. ; 94, s. 7549-7555
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Tidskriftsartikel (refereegranskat)abstract
- The self-association and solvent interaction of some polyethylene glycol alkyl ether surfactants (CxEy) in fornamide have been studied via determinations of phase diagrams and NMR self-diffusion measurements. For C12E3 and C12 E4, small micelles but no liquid chrystalline phases form. Increasing the alkyl chain length to hexadecyl (C16E4, C16E6, and C16E8), mesophase formation occurs analogously to the corresponding aqueous system. No aggregate growth occurs in the micellar phase, neither at high temperatures and high surfactant concentrations nor when approaching the lower consolute temperature. The solvent diffusion was analyzed within the cell diffusion model, and a concentration-independent amount of 1-5 and probably not more than 3 formamide molecules was found to interact with each ethylene oxide group. Furthermore, the calculations indicated a ploymer-like state of the micellar headgroup shell, with a slight decrease of the formamide content therein at a raised temperature. In conclusion, the behaviour of CxEy/formamide systems is qualitatively similar to that of the corresponding aqueous sytem.
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| 11. |
- Jönsson, A, et al.
(författare)
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Preparation and characterization of surface active erucic acid derivatives
- 1990
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Ingår i: Journal of the American Oil Chemists Society. - 0003-021X .- 1558-9331. ; 67, s. 733-738
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Tidskriftsartikel (refereegranskat)abstract
- Nonionic, cationic and anionic surfactants, derivatives of cis-13-docosenoic acid (erucic acid) have been prepared and characterized, and their performance has been evaluated and compared with the corresponding derivatives of fatty acids with shorter alkyl chain length. Nonionic erucic acid ethoxylates give a solution behavior anticipated from the hydropholic-lipophilc balance of the molecule; however, the incresed molecular size as compared to ordinary surfactants results, eg., in higher temperature stability of the surfactants aggregates. Anomalous solution behavior was found and investigated for anionic surfactants, trithanolammonium salts of erucic acid, and some shorter homolouges. The effects are discussed in terms of the asidbase equilibra of the alkanolammonium counterion and the acid, together with effects due to the molecular size of the counterion.
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| 12. |
- Lindström, A, et al.
(författare)
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Interactions in phospholipid stabilized emulsion system
- 1999
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Ingår i: Journal of Dispersion Science and Technology. - 0193-2691 .- 1532-2351. ; 20, s. 247-256
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between a phospholipid stabilized triglyceride emulsion and a hydrophilic silica surface has been studied at varying pH and electrolyte content using ellipsometry. The adsorbed amount decreases with pH and increases with increasing electrolyte content in the emulsion, and this can be rationalized on the basis of the electrostatic interaction between the emulsion droplet and the surface. The layer thickness, however, is essentially independent of these parameters. In addition, the emulsion has been studied during turbulent shear conditions (applied mechanical stress), with the same variation of pH and electrolyte as in the adsorption experiments. A decrease in pH and an increase in electrolyte content, decreasing the repulsive interaction between the droplets, leads to a deterioration in emulsion stability with time.
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| 13. |
- Malmsten, M, et al.
(författare)
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Electrostatic effects on interfacial film formation in emulsion systems
- 1996
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 179, s. 537-543
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption at silica from dilute emulsion systems was studied with in situ ellipsometry. In particular, the effects of electrostatic interactions on the adsorption rate and the adsorbed layer structure and formation was investigated by varying the emulsion droplet and surface charge, as well as the electrostatic screening, accomplished by varying pH and the excess electrolyte concentration. Electrostatic interactions were found to markedly affect the adsorption rate, but not the adsorbed layer structure or the mechanism for the adsorbed layer formation. For all cases investigated, the adsorbed layer thickness corresponds to emulsion droplets or multilamellar liposomes, and the adsorbed layer formation proceeds through attachment of emulsion droplets and/or multilamellar liposomes at the surface without extensive droplet spreading or liposome collapse. When the droplets and the surface are similarly charged, the adsorption is facilitated by increasing the electrostatic screening or by decreasing the emulsion droplet and surface charge, accomplished by increasing the excess electrolyte concentration and decreasing pH, respectively. When the droplets and the surface are oppositely charged, the adsorption rate is much higher than that observed when the droplets and the surface are similarly charged, although the adsorbed layer structure and the mechanism for the adsorbed layer formation are similar. Qualitatively, these effects may be understood by considering only electrostatic and van der Waals interactions.
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| 14. |
- Malmsten, M, et al.
(författare)
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Ellipsometry studies of interfacial film formation in emulsion systems
- 1995
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 173, s. 297-303
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Tidskriftsartikel (refereegranskat)abstract
- The possibility of using in situ ellipsometry for studies of the formation of interfacial films in emulsion systems was investigated. It was found that ellipsometry studies on dilute emulsion can provide information on both the adsorption kinetics, the adsorbed layer structure and the mechanisms for the adsorbed layer formation. At high electrolyte concentrations, the adsorption from a model o/w emulsion stabilized by egg lecithin was found to be more pronounced at hydrophilic and negatively charged silica than at hydrophobic methylated silica. Furthermore, the adsorbed layer thickness at both surfaces is smaller than the average droplet size, corresponding to either small or ”flattened” droplets or liposomes. The adsorbed layer thickness is smaller at methylated silica than at silica, presumably due to a larger degree of emulsion droplet or liposome spreading at this surface. In both cases, the adsorbed layer thickness is independent of the adsorbed amount, i. e. the adsorbed layer formation proceeds by attachment of droplets, which pack more densly with an increasing adsorbed amount.
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| 15. |
- Rippner Blomqvist, B, et al.
(författare)
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Disruption of visco-elastic β-lactoglobulin surface layers at the air-water interface by non-Ionic polymeric surfactants
- 2004
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 20, s. 10150-10158
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Tidskriftsartikel (refereegranskat)abstract
- Non-equilibrium interfacial layers formed by competitive adsorption of β-lactoglobulin and the non-ionic triblock co-polymer PEO99-PPO65-PEO99 (F127) to the air-water interface were investigated in order to explain the influence of polymeric surfactants on protein film surface rheology and foam stability. Surface dilatational and shear rheological methods, surface tension measurements, dynamic thin-film measurements, diffusion measurements (from fluorescence recovery after photo bleaching) and determinations of foam stability were used as methods. The high surface visco-elasticity, both the shear and dilatational, of the protein films was significantly reduced by co-adsorption of polymeric surfactant. The drainage rate of single thin films, in presence of β-lactoglobulin, increased with the amount of added F127, but equilibrium F127 films were found to be thicker than β-lactoglobulin films, even at low concentration of the polymeric surfactant. It is concluded that the effect of the non-ionic triblock copolymer on the interfacial rheology of £]-lactoglobulin layers is similar to that of low molecular weight surfactants. They differ however in that F127 increase the thickness of thin liquid films. In addition, the significant destabilising effect of low molecular weight surfactants on protein foams is not found in the investigated system. This is explained as due to that long-range steric forces start to stabilise the foam films at low concentrations of F127.
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| 16. |
- Sjöberg, M, et al.
(författare)
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2H Nuclear magnetic relaxation of 1.1-2H hexadecyltrimethylammonium bromide in micellar solutions of nonaqueous polar solvents and their mixtures with water
- 1990
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 6, s. 1205-1211
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Tidskriftsartikel (refereegranskat)abstract
- The 2H spin-lattice and spin-spin nuclear magnetic relaxtion rates were measured at different frequencies for α-deuterated hexadecyltrimethylammonium bromide in micellar solutions of nonaqueous and mixed solvent systems. Three nonaqueous polar solvents, viz., formamide, ethylene glycol, and N-methylformamide, and their mixtures with water were used. The two-step model for magnetic relaxation of surfactant aggregates was fitted to the frequency-dependent relaxation rates for the surfactant, yielding a local order parameter and correlation times for a fast local motion and for a slow aggregate motion. The measurements show that the surfactant aggregates in formamide, ethylene glycol, and their mixtures with water. No aggregation occurs in N-methylformamide at water contents lower than 50 wt%. Approximate aggregate radii, obtained from the slow correlation times, show that the aggregates formed in formamide and in ethylene glycol are smaller than in water. The local order parameter, obtained from the relaxation measurements as well as from the quadrupolar splittings in the hexagonal phases, increases with increasing water content both in the formamide and in the ethylene glycol systems.
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| 17. |
- Sjöberg, M, et al.
(författare)
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Non-aqueous surfactant systems
- 1997
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Ingår i: Liquid Detergents. - : Marcel Dekker. ; , s. 179-205
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Bokkapitel (refereegranskat)abstract
- Introduction: The interest in studying surfactant aggregation in other polar solvents than water has increased quite recently; indeed, much of the advances in the field are less than ten years old and the majority of that has been published during the last years. The research can be motivated, mainly, with two different types of arguments. First, the basic consideration of amphiphile aggregation such as a description of the hydrophobic interaction leading to e.g. micelle and liquid crystal formation. What can be learned from comparing water with other polar solvents? Much work has been performed to elucidate what properties of the solvent that are essential in order to obtain a hydrophobic (or "solvophobic") interaction. Comparisons of critical micelle concentrations in different solvents with parameters characterizing the solvent are numerous in the literature Second, there are technical applications where amphiphile aggregates and structures are needed to promote a specific effect, while circumstances may prevent the particular use of water due to certain reactions, corrosion problems and so on. Of particular interest in this context is e.g. alcohol based systems for cleaning purposes; another interesting area is chemical reactions in an aprotic solvent such as formamide. This review will deal with the first, fundamental point, in particular the formation of micelles and the mapping of phase equilibria. This is a logical starting point, since a prerequisite for most applied work in the field is some knowledge of the relevant phase diagrams. Methodological questions have often been raised when studying non-aqueous systems, since many early studies on micellization were performed using indirect methods for detecting aggregation. This has caused considerable confusion due to apparently unreconcilable results. Also, recently, several studies have pointed out the difference between a proper micellization process and ordinary aggregation. As will be discussed later, depending on combination of solvent and surfactant, it is possible to have a cooperative aggregation (micelle formation) as well as a more gradual aggregation process.
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| 18. |
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| 19. |
- Solans, C, et al.
(författare)
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Phase behaviour of cationic lipoaminoacid surfactant systems
- 1989
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 79, s. 70-75
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Tidskriftsartikel (refereegranskat)abstract
- Alkyl esters of long chain basic aminoacids are know as cationic surfactants which have a very good solubility in water; many of them possess antimicrobial properties and are generally considered milder and less irritant than other surfactants. Long chain Nα-acyl-L- α-amino- ω-guanidine alkyl acid derivatives have recently been synthesized. Physico-chemical and antimicrobial studies of these compounds as a function of the alkyl ester or sodium salt (R), the straight chain length of the fatty acid residue (x) and the number of carbons between the ω-guanidine and α-carbxyl group (n) were carried out. Among the different aminoacid surfactant derivatives synthesized, the methyl ester of Nα-lauroyl arginine (LAM) showed higher activity of both surface and antimicrobial properties. In this study, some fundamental studies on LAM phase behavior in binary and multicomponent systems have been undertaken. The phase equilibria has been determined in the binary LAM/water and ternary LAM/water/alkanol systems. Solubilization of nonpolar compounds such as hydrocarbons has also been investigated.
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| 20. |
- Stålgren, J, et al.
(författare)
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Adsorption of liposomes and emulsions studied with a quartz crystal microbalance
- 2001
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Ingår i: Advances in Colloid and Interface Science. - 0001-8686 .- 1873-3727. ; 89, s. 383-394
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Tidskriftsartikel (refereegranskat)abstract
- The QCM (Quartz Crystal Microbalance) is an ultra sensitive weighing device based on the piezoelectric, electromechanical oscillator principle. It consists of a thin single-crystal quartz disk, with one metal electrode deposited on each side. When the electrodes are connected to an electric oscillator, the crystal can be made to oscillate in a very stable manner at its resonance frequency, f. When a mass is adsorbed on one or both of the electrodes, then this leads to a change in the resonance frequency of the quartz crystal. If the adsorbed mass is small compared to the mass of the quartz crystal and there is no slip or deformation due to the oscillatory motion, then the resonance frequency decreases proportionally to the mass of the adsorbed film. It is possible to determine very small changes of the resonance frequency and hence very small mass changes, since the QCM generally has very stable oscillations. However, there are situations where the change in resonance frequency is not linearly related to the change in deposited mass, for example, when the mass is not rigid, slipping on the surface, or not deposited evenly over the electrode(s). There are also other things besides an applied mass that can influence the resonant frequency of a QCM including electrical effects, pressure, and temperature. In this diploma work the interaction between hydrophilic potassium mica surface and hydrogen mica surface and airs of different humidities have been investigated. The resulting adsorption isotherms show how much water that is adsorbed on the two surfaces.
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| 21. |
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| 22. |
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| 23. |
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| 24. |
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| 25. |
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| 26. |
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| 27. |
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| 28. |
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| 29. |
- Wärnheim, T, et al.
(författare)
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NMR studies of aggregation in the octylamine/water system
- 1992
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Ingår i: Organized Solutions. - : Marcel Dekker. ; , s. 221-235
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Bokkapitel (refereegranskat)abstract
- INTRODUCTION; Short chain alkylamines, such as octylamine, constitute a technically important group of amphiphiles. They are used as hydrophobing agents, emulsifiers, and as flotation agents. Their solution chemistry, however, has received relatively little attention. In the case of octylamine, phase diagrams have been reported for the binary aqueous system [1,2] and for the ternary system with added pxylene [3-5]. For octylamine/water solutions a lower consolute temperature (LCT) occurs at 25°C for a critical concentration of 10 wt % surfactant. The presence of a LCT is caused by a complex interplay of temperature dependent interactions, the origins of which are poorly understood for the system presently under studz corresponding phenomena in surfactants of the poly(ethylene oxide) type are at present a subject of intense discussion [6]. We feel that an understanding of the clouding phenomena in the octylamine system is desirable, although we make little attempts in the present study to explain it. Rather, we report a study of the aggregate size/shape in the isotropic solution phase in the octylamine/water system, since these quantities are necessary starting points when discussing the clouding phenomenon. Thus we have investigated the octylamine system by means of NMR methods. From 2H multifield relaxation rate measurements of a deuterated octylamine, it is possible to deduce quantitative information on the reorientational dynamics of the surfactant molecules . We have used the two step model for the interpretation of the measured relaxation rates t7,8]. In this model the motion of the aggregated surfactant is separated into two time regimes: a fast regime corresponding to the local motion of the molecule within the aggregate, and a slow regime corresponding to the global motions of the aggregate and/or surfactant lateral diffusion over the curved aggregate surface. We have also used multicomponent selfdiffusion measurements, which give an opportunity to judge whether an individual component is confined to an aggregate or not [9]. They also serve as a critical test of the interpretation of the relaxation data, since the suggested structures and their dimensions must not be at variance with the selfdiffusion data.
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| 30. |
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| 31. |
- Wärnheim, T, et al.
(författare)
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Phase behaviour of alkanolammonium carboxylates
- 1992
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 88, s. 18-22
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Tidskriftsartikel (refereegranskat)abstract
- Partial binary phase diagrams for thirteen different alkanolammonium carboxylates with water have been determined. The alkanolamines employed were monoethanolamine, triethanolamine and triisopropanol--amine, while the fatty acid has been varied with respect to chain length (C8 - C22) and saturation. The phase diagrams show the features that distinguish them from ordinary soap-water phase diagrams. First, multi-phase regions and miscibility gaps occur at low concentrations of surfactant, in particular for triethanolammonium carboxylates. Secondly, the stability regions of the liquid crystalline phases are different, and in general smaller com--pared to those formed by the corresponding alkali carboxylates. It is suggested that the first feature is due to that alkanolamines are weak bases and thus, that any surfactant aggregate comprises a few percent of unhydrolyzed acid, while the second feature is attributed to the larger size of the counterion compared to alkali ions, which tends to destabilize ordered structures.
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| 32. |
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| 33. |
- Wärnheim, T, et al.
(författare)
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Phase diagrams for cationic surfactants in polar solvent systems
- 1990
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 82, s. 271-279
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Tidskriftsartikel (refereegranskat)abstract
- Phase diagrams are presented for cationic surfactants, and alkyltrimethyl ammonium bromide in polar solvent systems, such as ethylene glycol, formamide, glycerol, and their mixtures with water. Provided that the solvent is sufficiently lipophobic, and that the hydrocarbon moiety of the surfactant is sufficiently large, liquid crystalline phases form according to the normal association pattern for ionic surfactants. In, for example, ethylene glycol, liquid crystals are only formed with surfactants with a longer alkyl chain length than dodecyl.-The formation of didodecyldimethylammonium bromide microemulsions containing polar solvents- mainly formamide, water and their mixtures-and hydrocarbon has been studied. The extension of the solution phase region may decrease, although the mutual miscibility of polar solvent and the hydrocarbon increases. NMR self-diffusion measurements reveal that this is accompanied by a corresponding loss of structure, i.e., a smaller distinction between polar and apolar regions.
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| 34. |
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| 35. |
- Wärnheim, T, et al.
(författare)
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Surfactant aggregation in systems containing alkanol amines and fatty acids
- 1990
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 138, s. 314-323
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Tidskriftsartikel (refereegranskat)abstract
- The phase diagrams of six different alkanolammonium carboxylate-water systems have been determined. Their phase behavior differs from that of ordinary soaps, since there are large differences between the systems for varying alkyl chain lengths of the carboxylate. In addition, the chemical structure of the alkanolammonium counterion also affects the phase equilibria. For short alkyl chain carboxylates the liquid crystalline phases disappear (e.g., for triethanolammonium octanoate) or decrease in extension (e.g., for monoethanolammonium octanoate), although the surfactant readily aggregates in solution. In contrast, long alkyl chain carboxylates behave like swelling amphiphiles with a low aqueous solubility and the immediate formation of a lamellar phase (e.g., for tri-and monoethanolammonium oleate). It is shown that the distrubition between acid and soap causes these effects. The lower surface charge of the surfactant aggregates compared to that of orinary soap micelles is also reflected in a lowering of the critical micellization concentration.
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| 36. |
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| 37. |
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