Micelles. Structure and catalysis (original) (raw)
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Mixed micellization of octaoxyethylene monododecyl ether and n-alkyltrimethylammonium bromides
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2003
The micellization process of binary mixtures formed by octaoxyethylene monododecyl ether (C 12 E 8 ) and three different n -alkyltrimethylammonium bromides, including dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), and cetyltrimethylammonium bromide (CTAB), was examined by using the fluorescence probing method. The critical micelle concentration values were determined by the pyrene 1:3 ratio method. The experimental data were analyzed on the light of various mixing thermodynamic models within the framework of the pseudophase separation model. In all the cases, a negative deviation from the ideal behavior was found. However, the interaction parameter (b 12 ), as reported by the regular solution theory, was found to be dependent on the micellar composition. It was established that, in addition to the electrostatic interactions between the headgroups of the surfactants, secondary effects of steric character due to the different length of the alkyl chain of the nalkyltrimethylammonium bromides must be taken into account to justify the experimental data. The mixing thermodynamic functions for the C 12 E 8 Á/CTAB system were determined. The change in the micellization entropy was interpreted in connection with the hydration status of the mixed micelles. The increase observed in the micellar micropolarity with the content of the ionic component, which was consistent with the corresponding change in the micellization entropy, was attributed to the formation of more open micelles with a more hydrated structure. Data obtained in this study suggest that in the case of the C 12 E 8 Á/DTAB and C 12 E 8 Á/TTAB systems, with considerable differences in the critical micelle concentration values, pure non-ionic micelles are formed in the range of low proportion of the ionic component. #
Theory of micelle formation by amphiphilic side-chain polymers
Macromolecules, 1990
A microscopic model for the formation of micelles by amphiphilic side-chain polymers is developed. The model predicts the free energy, the size of the micelles, and the micellar phase composition. Characteristic values are calculated for the number of backbone segments and the length of the hydrophobic side chains beyond which only single molecule micelles form. The effects of salt concentration, polymer volume fraction, and polymer dimensions on the composition of the micellar phase and micelle size distribution are discussed,
Journal of Physical Organic Chemistry, 1991
Two amphiphilic oximes, 10-phenyl-10-hydroxyiminodecanoic acid (oxime 11) and 4-(9-carboxynonanyl)-l-(9-carhoxy-1-hydroxyimino nonany1)benzene (oxime 111) were synthesized. The pK. values of oximes I1 and I11 and acetophenoxime (oxime I) and the rates of oximolysis of p-nitrophenyl acetate (NPA) and p-nitrophenyl octanoate (NPO) were determined in the presence and absence of micellar hexadecyltrimethylammonium bromide (CTAB). The rates of oximolysis increased by up to 3 x 104-fold in the presence of CTAB. Quantitative analysis of micellar effects, using an ion-exchange pseudo-phase model, allowed the determination of the second-order rate constants for the reactions of oximes 1-111 with NPA and NPO in the micellar pseudo-phase. The calculated rate constants in the micellar pseudo-phase were lower than those in water, demonstrating that the rate enhancements were due to substrate concentration in the micelles. Comparison of the rate constants in micelles and water suggests that the sites of reaction of oximes 1-111 with NPO and NPA are similar to those in hulk aqueous solution. Micellar incorporation of the hydrophobic oximes I1 and I11 does not lead to a major change in the nucleophilicity of the oximate anion.
Influence of Alcohol on the Behavior of Sodium Dodecylsulfate Micelles
Journal of Colloid and Interface Science, 1998
ing neutral salt and a medium chain alcohol . There-The effect of medium chain alcohol molecules on the size and fore, these elements make the basic components in most shape of sodium dodecylsulfate micelles, and on the self-diffusion microemulsions. However, the intricate behavior of these coefficient of the surfactant and alcohol, has been investigated by mixed micellar aggregates makes it difficult to predict any means of small angle neutron scattering (SANS), and Fourier variation in the system upon variation in the composition of transform pulsed field gradient spin echo (FT-PGSE) nuclear the solution. This problem is caused by a delicate balance magnetic resonance measurements. All measurements were done of attractive and repulsive forces among the amphiphilic in D 2 O containing a sodium chloride concentration of 0.4 mol/kg, molecules in the micelles. and a surfactant concentration of 0.04 mol/kg. The alcohols used
Theoretical and Experimental Chemistry, 2007
The reactivity of co-micelles of functional/cationic surfactants [functional surfactants-1-cetyl-3-(2-hydroxyiminopropyl)-, 1-cetyl-3-(2-amino-2-hydroxyiminoethyl)-, and 1-cetyl-3-(2-hydroxyaminoethyl-2-onyl)imidazolium chlorides, cationic surfactants-1-cetyl-3-methylimidazolium and cetyltrimethyl-ammonium chlorides] toward the 4-nitrophenyl esters of diethylphosphoric, diethylphosphonic, and toluenesulfonic acids was investigated. It was shown that the nucleophilicity of the functional groups in the surfactant does not undergo substantial changes with variation in the nature of the head group of the cationic surfactant and the fraction of functional detergent in the co-micelle. This makes it possible to create systems that decompose organophosphorus substrates unusually quickly even with small contents of the functional surfactant.
Multicomponent Reactions Accelerated by Aqueous Micelles
Frontiers in Chemistry, 2018
Multicomponent reactions are powerful synthetic tools for the efficient creation of complex organic molecules in an one-pot one-step fashion. Moreover, the amount of solvents and energy needed for separation and purification of intermediates is significantly reduced what is beneficial from the green chemistry issues point of view. This review highlights the development of multicomponent reactions conducted using aqueous micelles systems during the last two decades.
2018
Classically, polymer micelles have been defined as aggregates formed by the self-association of amphiphilic polymers due to the hydrophobic interactions between polymer molecules in water. Practical applications of polymer micelles include as carriers in drug delivery systems, as solubilizers, and as associative thickeners. Polymer micelles that do not fall within the classical definition have recently been reported and reflect important developments in synthesis and analysis. For example, hydrophobic interactions are the classic force driving polymer association, whereas recently, micelles have been formed through interactions such as electrostatics, hydrogen bonds, and coordination bonds. Intermolecular association results in the formation of polymer micelles that are similar to micelles formed from low molecular weight surfactants, whereas unimolecular micelles formed by intramolecular association within a single polymer chain have also been reported, as have stimuli-responsive p...
A Review of Polymeric Micelles and Their Applications
Polymers
Self-assembly of amphiphilic polymers with hydrophilic and hydrophobic units results in micelles (polymeric nanoparticles), where polymer concentrations are above critical micelle concentrations (CMCs). Recently, micelles with metal nanoparticles (MNPs) have been utilized in many bio-applications because of their excellent biocompatibility, pharmacokinetics, adhesion to biosurfaces, targetability, and longevity. The size of the micelles is in the range of 10 to 100 nm, and different shapes of micelles have been developed for applications. Micelles have been focused recently on bio-applications because of their unique properties, size, shape, and biocompatibility, which enhance drug loading and target release in a controlled manner. This review focused on how CMC has been calculated using various techniques. Further, micelle importance is explained briefly, different types and shapes of micelles are discussed, and further extensions for the application of micelles are addressed. In t...
Polymeric Micelles: General Considerations and their Applications
Ind J Pharm Edu Res, 2011
One of the most widely studied subjects in nanoscience technology is related to the creation of supramolecular architectures with well-defined structures and functionalities. These supramolecular structures are generated as a result of self-assemblage of amphiphilic block polymers. Self-assembly of block polymers via hydrophobic and hydrophilic effects, electrostatic interactions, hydrogen bonding, and metal complexation has shown tremendous potential for creating such supramolecular structures with a wide array of applications. Polymeric micelles have gathered considerable attention in the field of drug and gene delivery due to their excellent biocompatibility, low toxicity, enhanced blood circulation time, and ability to solubilize a large number of drugs in their micellar core. In this article we have reviewed several aspects of polymeric micelles concerning their general properties, preparation and characterization techniques, and their applications in the areas of drug and gene delivery. Polymeric micelles can be used as 'smart drug carriers' for targeting certain areas of the body by making them stimuli-sensitive or by attachment of a specific ligand molecule onto their surface.