Transition from a nonionic to an ionic micelle

Kelkar, V. K.; Mishra, Bijaya Kumar; Rao, K. Srinivasa; Goyal, P. S.; Manohar, C.

doi:10.1103/physreva.44.8421

Cited by 14 publications

(8 citation statements)

References 15 publications

(22 reference statements)

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“…As τ c (the value at which the stickiness parameter becomes sufficiently large to cause the micelles to flocculate) was approached, the system went directly from a single phase of micelles dominated by repulsive interactions to a flocculant. Using this approach, we were able to reproduce the results of earlier studies, 51,55,56 which predicted micelle growth at much higher volume fractions by aggregation of hard, sticky spheres and of charged, sticky spheres. Thus, we were not successful in using the Baxter approach to understand aggregation and growth in the conjugated bile saltfatty lipid systems at these relatively low concentrations.…”

Section: Discussionmentioning

confidence: 65%

Structure of Conjugated Bile Salt−Fatty Acid−Monoglyceride Mixed Colloids: Studies by Small-Angle Neutron Scattering

et al. 1999

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The structures of particles found in isotropic phases of mixed surfactant systems consisting of conjugated bile salts and fatty lipids were assessed using small-angle neutron scattering. The conjugated bile salts were either cholylglycine or chenodeoxycholylglycine. The fatty lipids were mixtures of oleate and oleic acid either alone or with monoolein. The scattering data suggested that both particle interactions and polydispersity must be modeled in these systems. Particle interactions were modeled using the reduced mean spherical approximation and the decoupling approximation. Maximum entropy was used to characterize the polydispersity. A self-consistent analysis of the scattering was arrived at by making an initial estimate of particle size and shape using derivative−log and Guinier analysis and refining the estimates by analyzing the particle interactions and polydispersity and iterating. The scattering at high total lipid concentrations was consistent with globular mixed micelles with repulsive electrostatic interactions. The globular mixed micelles in these systems were similar in size and shape to those observed previously in conjugated bile salt mixtures with either egg yolk phosphatidylcholine or monoolein. Solutions of cholylglycine with monoolein and oleate/oleic acid underwent a transition to vesicles at lower concentrations. This behavior was similar to those observed in conjugated bile salts with either egg yolk phosphatidylcholine or monoolein. Cholylglycine mixtures with oleate/oleic showed somewhat different behavior at lower concentrations, since there was also evidence for coexistence of elongated and tabletlike micelles. Despite these differences, there were sufficient similarities in the particle morphologies of these and other conjugated bile salt−fatty lipid systems to suggest a common mode of self-assembly. These solutions are models for bile in the bilary system and intestine content during triglyceride digestion; the common themes of self-assembly have implications for the physiology of lipid solubilization in bile as well as intestinal absorption of dietary lipids.

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Section: Discussionmentioning

confidence: 65%

Structure of Conjugated Bile Salt−Fatty Acid−Monoglyceride Mixed Colloids: Studies by Small-Angle Neutron Scattering

et al. 1999

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“…Addition of Bu 4 N + , Bu 4 P + , or Am 4 N + to solutions of TX-100 increases the CP (Figure A), which may be due to the fact that the hydrophobic nature of these counterions would enable them to interact favorably with TX-100 micelles while a positive charge on them would introduce electrostatic repulsion between the micelles (due to adsorption at the micellar surface). CP increase has been observed in nonionic surfactant solutions on the addition of different organic acids/salts and also a few ionic surfactants. − The increase in CP by quaternary ions is generally considered to be due to the more favorable interaction between water and the poly(ethylene oxide) (PEO) chains . It is further suggested that such salts affect the solvation capacity of water in relation to the PEO units, especially at higher temperatures .…”

Section: Resultsmentioning

confidence: 99%

Temperature−[Salt] Compensation for Clouding in Ionic Micellar Systems Containing Sodium Dodecyl Sulfate and Symmetrical Quaternary Bromides

2003

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“…CP increase has been observed in nonionic micellar solutions on the addition of different organic acids/salts and also a few ionic surfactants. [16][17][18][19][26][27][28][29][30] As shown by Valaulikar and Manohar, 19 addition of the latter to solutions of nonionic surfactants increased the CP by introducing electrostatic repulsion between the resultant mixed ionic micelles. They further demonstrated that the increase in CP could be described in terms of the surface charge per micelle.…”

Section: Resultsmentioning

confidence: 99%

Salt−Induced Cloud Point in Anionic Surfactant Solutions: Role of the Headgroup and Additives

et al. 2002

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Anionic surfactants are not known to show a clouding phenomenon in aqueous solutions. On the other hand, this is a general feature for nonionic surfactants. Here the effect of addition of tetra-n-butylammonium bromide (Bu4NBr) on the clouding phenomenon in sodium dodecylbenzenesulfonate (SDBS) has been studied by measuring cloud points (CP) for each combination. Similar type of studies were also performed with poly(ethylene glycol) t-octylphenyl ether (TX-100). The CP varies in an opposite manner for the two classes of surfactants, which is explained in terms of charge variation in each type of micelles by the addition of Bu4NBr. A relationship between [SDBS] vs [Bu4NBr] has been worked out for getting the CP − phenomenon in SDBS solutions: nearly one Bu4NBr molecule is needed for each two SDBS monomers for getting the CP in the system. With 10-mM SDBS, the addition of Bu4NBr shows an interesting phase behavior, where a stable colloidal phase with bluish − white appearance (preclouded) appears preceded by conventional clouding. Effects of the addition of ureas (urea and tetramethylurea), thioureas (thiourea and tetramethylthiourea), amino acids (glycine, alanine, leucine and phenylalanine), and sugars (xylose, arabinose and dextrose) have also been seen on the 50-mM SDBS + 35-mM Bu4NBr system (this system was chosen because its CP has a wider window available for variations below and above the CP). Ureas and thioureas affect the CP in different manners, which are explained in the light of indirect and direct interactions with micelles. CP variation in the presence of amino acids depends on their polar and hydrophobic nature. On the other hand, sugars behave in a manner similar to their effect on solubility of hydrophobic compounds in aqueous solutions.

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Transition from a nonionic to an ionic micelle

Cited by 14 publications

References 15 publications

Structure of Conjugated Bile Salt−Fatty Acid−Monoglyceride Mixed Colloids: Studies by Small-Angle Neutron Scattering

Structure of Conjugated Bile Salt−Fatty Acid−Monoglyceride Mixed Colloids: Studies by Small-Angle Neutron Scattering

Temperature−[Salt] Compensation for Clouding in Ionic Micellar Systems Containing Sodium Dodecyl Sulfate and Symmetrical Quaternary Bromides

Salt−Induced Cloud Point in Anionic Surfactant Solutions: Role of the Headgroup and Additives

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