Structure micellization

Letchford K, Burt H (2007) A review of the formation and classification of amphiphilic block copolymer nanoparticulate structures micelles, nanospheres, nanocapsules and polymersomes. Eur J Pharm Biopharm 65 259-269... 

As introduced previously, type 2 ABC triblock copolymer micelles are formed by triblock copolymers containing an insoluble A block while the B and C blocks are soluble in the considered solvent. The insoluble blocks can be located either between the two soluble blocks (BAC structure) or at one end of the triblock (ABC or ACB structures). Micelles of the latter type were discussed above for, e.g., PS-P2VP-PEO pH-responsive micelles and are indeed considered as core-shell-corona, onion, or three-layer structures since the heterogeneity in the micellar corona is observed in the radial direction (Fig. 18). Micelles formed by BAC triblock copolymers are different from the previous case because they can give rise in principle to a heterogenous corona in the lateral dimension (Fig. 18). This could induce the formation of noncentrosymmetric micelles as discussed in Sect. 7.3. 

During the end of the 20th century, a surge in the development of significantly advanced techniques has advanced nanoscience and technology in the development of self-assembly structures—micelles, monolayers, vesicles—biomolecules, biosensors, and surface and colloidal chemistry. In fact, the current literature indicates that there is no end to this trend regarding the vast expansion in the sensitivity and level of information. 

It was concluded that definition of asphaltenes based only on solubility is not a satisfactory criterion and that the behavior of asphaltenes in chromatographic separations is incompatible with such structures where the polymer units are interconnected predominantly by a-bonds. The asphaltenes are a complex state of aggregation best represented by the stacked cluster structure (micelle), which, however, cannot explain some of the GPC behavior of very dilute asphaltene solutions. 

Studies of fluorescence of probe molecules [30] in ionic liquids revealed red shifts which are characteristic of organized media with long-lived structures (micelles). The fluorescence of the ionic liquids themselves shows the same signs [31], This can also be an indication of glassy dynamics. 

Absalan, G., Hemmateenejad, B., Soleimani, M., Akhond, M. and Miri, R. (2004) Quantitative structure-micellization relationship study of... 

Coexistence of additional colloidal structures (micelles, liposomes, supercooled melts, drug nanoparticles) and timescale of distribution processes... 

S. Priyanto, G.A. Mansoori, A. Suwono, Measurement of property relationships of nano-structure micelles and coacervates of asphaltene in a pure solvent . Chemical Engineering Science, 56, 6933-6939, (2001). 

In contrast, micelles have long been recognized as simple chemical models for biomembranes [29]. Indeed, structurally, micelles are more similar to biomembran than 1 -octanol or RPLC stationary phases. Several researchers have demonstrated that the solubilization (or partitioning of solutes) into micelles closely resembles that of lipid bilayers. Both micelles... 

Surfactant molecules are amphiphilic and associate together in aqueous solution to form various structures micelles, microemulsions, vesicles, lyotropic liquid crystalline phases. In each case, their alkyl chains group together and their polar heads form a layer which separates them from the water. The laws governing this self-assembly involve subtle combinations of the two principles, order and mobility. Some fascinating illustrations are provided by the cell membrane in biological systems. In this case, order and mobility are related to the structure of functional units made up of lipids and proteins [6.10]. Such examples could only encourage chemists to carry out novel syntheses which would produce molecules capable of self-assembly. 

The properties of surfactant molecules properties are (i) their ability to form different aggregate structures (micelles) above die critical micellar concentration (CMC), (ii) their ability to solubilize water-insoluble organic molecules (M) by hydrophobic-hydrophobic interactions, and (iii) their adsorption on electrodes changes the solution-metal interface, which alters redox reactions and produces template effects on the electrode surface (79) (Schem 2). SDS can be used to electropolymerize various thiophene derivatives such as EDOT, BT and MOT in aqueous solution. 

Dynamic surface tension is an important property of a surfactant solution and a recent book [14] provides an excellent review of the area. However, the effects that surfactant type and structure, micelle formation, CMC, and equilibrium tension have on the decay of surface tension with time (y(t)) are still unclear. The Ward and Tordai equation [15] describes the diffusion-controlled... 

Although size reduction through homogenization as well as homogeneity of the dispersions can be improved with increasing stabilizer concentration/ - the amount of stabilizer(s) should be hold as low as possible due to the irritation potential and hemolytic properties of this class of excipients. Furthermore, excess of stabilizer(s) may lead to the formation of additional colloidal structures (micelles, liposomes) where the drug may also be localized. 

We are interested mainly in making the difference between (A) and (B) small—i.e., in small x values. Then some compatibility can be maintained. It is important that the chemical sequence of B be statistical in particular, the number of V units (jcNb) must be much larger than 1 (although x is small). Then it is possible to show (using the methods of Chapter X) that the V units will not lend to segregate locally by building up micelles or other oiganized structures. Micelles seem to be compatible only with well-defined periodicities in the chemical sequence of the (B) chains. 

Supramolecular Structured Micelles Based on Cyclodextrin for Drag Delivery 225... 

The main purpose of the present contribution is to explore the correlation between the structure, micellization ability and hemolytic activity of three series of single-head single-tail saccharide surfactants [4,10] along with dicephalic (doubleheaded) [11] and gemini (dimeric) representatives [3,5], whose structure and abbreviations are shown in Scheme 1. 

A slightly different approach to the formation of onion type micelles is that described by Prochazka etal. [275], Such structured micelles could be obtained by starting with PtBA-P2 VP... 

Ortiz, D. P. Baydaka, E.N. Yarranton H.W.(2010). Effect of surfactants on interfacial films and stability of water-in-oil emulsions stabilized by asphaltenes. Journal off Colloid and Interface Sdence,doi 10.1016/j.jcis.2010.08.032 Pryanto, S., Mansoori, G.A., Suwono, A., (2001). Measurement of property relationships of nano-structure micelles and coacervates of asphaltene in a pure solvent. Chemical Engineering Science, 56, 6933-6939... 

Salt-free dilute solutions of 12-2-12, 2Br" (surfactant volume fraction below 1%) show shear-induced structuration (micelle growth) resulting in an increase of viscosity, as illustrated in Fig. 16 [118]. 

Amphiphilic molecules [11-14] consist of mutually incompatible components. Since these components are chemically joined, complete segregation is impossible. It is replaced by various forms of microphase separation. These involve formation of segregated domains such that at least one of their dimensions is comparable to the molecular size. The domains are formed by spontaneous, thermodynamically driven aggregation of the amphiphiles. The process is thus often referred to as self-assembly. The resulting structures, micelles, lamellae, etc. can also form ordered mesophases. The microphase separation can take place in a solvent that selectively solubilizes one component or in a melt of neat amphiphiles. These characteristics are common to both polymeric and monomeric, low molecular weight amphiphiles. For the purposes of our discussion monomeric amphiphiles are defined, somewhat arbitrarily, as those consisting of 10 atoms. Polymeric amphiphiles, on the other hand, can incorporate 10 -10 atoms. The consequences of this difference are the topic of this article. 

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