Micelle shape spherical

They are repulsive and work perpendicular to the interface. Repulsive interactions induce micelle ordering at values of the surfactant volume fraction and with symmetry that depend on the micelle shape.Spherical micelles close pack into a cubic array, forming the discontinuous cubic phase I. Rodlike micelles pack into a hexagonal array, forming the hexagonal phase H. Bilayers pack into the lamellar phase An important point is that this simple approach leads one to predict for a surfactant that forms spherical micelles (P < 1/3) the following sequence of phases as the surfactant concentration is increased ... 

Between 5 and 23 minutes, a continuous evolution is observed, characterised by the increase of the intensity at low q and by the q"1 slope in a log-log plot that is the signature of ID objects (figure 3). This corresponds to the transformation of the shape of the micelles from spherical to cylindrical and their continuous growth in length up to few tens of nanometers. The increase of turbidity in solution is related to the growth of the micelles, and coincides with the beginning of the condensation of silica. 

The micelles are spherical, but when the concentration of surfactant increases, the shape of the ionic micelles changes following the spherical sequence cylindrical-hexagonal-laminar [22], In the case of nonionic micelles the shape... 

Miller et al have reported that in bile salt solutions in the presence of EL, if the EL concentration is less thcin half of that of the bile salts, the mixed micelle shape beccmes spherical, but, otherwise, the shape is a disk as shown in Figure 2. All solutions used here inclixie 32 mM lecithin and 100 mM total bile salts, therefore the micelle shape in all systems here must be spherical. Edward et al... 

In aqueous solution, amphiphilic molecules aggregate into micelles above the critical micelle concentration. Such solutions have been the object of research for many years, with special interest in shape and size of these micellar aggregates [37]. Size and shape (spherical, wormlike, or disklike micelles) depend strongly on the molecular structure of the amphiphilic molecule. 

The vast majority of polymer micelles have spherical shape in dilute or semidilute solutions, whereas low-molecular-weight surfactants form structures that are strongly concentration dependent lamellae, sheets, rods, and spheres. 

In Fig. 2, a variety of micelle structures are shown. Typical shapes of micelles are spherical, rod-like, and worm-like. At high concentrations of surfactant or at high concentrations of counterions, liquid crystals are usually formed. Hexagonal, cubic, and lamellar are common liquid crystal phases that occupy much of a... 

The initial publications did not emphasize the specific action of the hydrotrope molecules in different applications. Instead they considered the structural modification of aqueous micelles by the addition of hydrotrope. Assessing the results from this point of view [61-64] the conclusion was that the reduction of electrostatic repulsion is the main cause of the modification of surfactant micelles from spherical to cylindrical shape after addition of a hydrotrope with opposite charge. 

The value of o varies not only with the structure of the hydrophilic head group, but also with changes in the electrolyte content, temperature, pH, and the presence of additives in the solution. Additives, such as medium-chain alcohols that are solubilized in the vicinity of the head groups (Chapter 4, Section IIIA), increase the value of oq. With ionic surfactants, o decreases with increase in the electrolyte content of the solution, due to compression of the electrical double layer, and also with increase in the concentration of the ionic surfactant, since that increases the concentration of counterions in the solution. This decrease in the value of ao promotes change in the shape of the micelle from spherical to cylindrical. For POE nonionic surfactants, an increase in temperature may cause a change in shape if temperature increase results in increased dehydration of the POE chain. 

In the case of ordered mesoporous oxides, the templating relies on supramolecular arrays micellar systems formed by surfactants or block copolymers. Surfactants consist of a hydrophihc part, for example, ionic, nonionic, zwitterionic or polymeric groups, often called the head, and a hydrophobic part, the tail, for example, alkyl or polymeric chains. This amphiphiUc character enables surfactant molecules to associate in supramolecular micellar arrays. Single amphiphile molecules tend to associate into aggregates in aqueous solution due to hydrophobic effects. Above a given critical concentration of amphiphiles, called the critical micelle concentration (CMC), formation of an assembly, such as a spherical micelle, is favored. These micellar nanometric aggregates may be structured with different shapes (spherical or cylindrical micelles, layered structures, etc. Fig. 9.8 Reference 70). The formation of micelles. 

Micelle size (aggregation number) varies according to micelle shape and alkyl chain length. Spherical micelles always have low aggregation numbers, due to the micelle ra-... 

Molecular dynamics simulations are consistent with calculations based on the critical packing parameter p, which indicate that the structure of the surfactant controls the shape of the micelle at the cmc. Esselink et al. [16] show that the surfactants / 2/5, hihts, and h thts form bilayers, cylindrical micelles, and spherical micelles, respectively, as expected. However, /14/4, expected to form micelles of low curvature based on p, instead forms sphere-like structures due to the coiling of the headgroup. If this increased effective headgroup area is accounted for in the calculation of the packing parameter, then a spherical shape is predicted, in agreement with the result of the simulations. 

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