Micelle internal

Huppertz, T., de Kruif C.G. (2008). Structure and stability of nanogel particles prepared by internal cross-linking of casein micelles. International Dairy Journal, 18, 556-565. 

Guetzlhoff TF, Rice JA (1992) Does humic acid form a micelle . International Conference on Organic Substances in Soils and Sediments, Lan-chester, UK... 

In some of these models (see Sec. Ill) the surfactants are still treated as flexible chains [24]. This allows one to study the role of the chain length and chain conformations. For example, the chain degrees of freedom are responsible for the internal phase transitions in monolayers and bilayers, in particular the hquid/gel transition. The chain length and chain architecture determine the efficiency of an amphiphile and thus influence the phase behavior. Moreover, they affect the shapes and size distributions of micelles. Chain models are usually fairly universal, in the sense that they can be used to study many different phenomena. 

Amphiphilic molecules (surfactants) are composed of two different parts hydrophobic tail and hydrophilic head [1 ]. Due to their chemical structure they self-assemble into internal surfaces in water solutions or in mixtures of oil and water, where the tails are separated from the water solvent. These surfaces can form closed spherical or cylindrical micelles or bicontinuous phases [3,5]. In the latter case a single surface extends over the volume of the system and divides it into separated and mutually interwoven subvolumes. 

S. Carra, M. Morbidelli, and G. Storti, in Proceedings of the International School of Physics Enrico Fermi, Course XC Physics of Amphiphiles Micelles, Vesicles and Microemulsions (V. Degiorgio and M. Corti, ed.), North-Holland, Amsterdam, 1985, pp. 483-512. 

From experience in metalworking applications it is known that ether carboxylates may improve the existing corrosion protection of formulations [66]. From pKj studies described by Aalbers [49], an internal neutralization of the ether carboxylate micelles can be concluded resulting in less anionic character than, for example, alkyl sulfates therefore also combination with quats are possible without any problem. 

The frequent breaking and reforming of the labile intermolecular interactions stabilizing the reversed micelles maintain in thermodynamic equilibrium a more or less wide spectrum of aggregates differing in size and/or shape whose relative populations are controlled by some internal (nature and shape of the polar group and of the apolar molecular moiety of the amphiphile, nature of the apolar solvent) and external parameters (concentration of the amphiphile, temperature, pressure) [11], The tendency of the surfactants to form reversed micelles is, obviously, more pronounced in less polar solvents. 

Solutions of surfactant-stabilized nanogels share both the advantage of gels (drastic reduction of molecular diffusion and of internal dynamics of solubilizates entrapped in the micellar aggregates) and of nonviscous liquids (nanogel-containing reversed micelles diffuse and are dispersed in a macroscopicaUy nonviscous medium). Effects on the lifetime of excited species and on the catalytic activity and stability of immobilized enzymes can be expected. 

The concept of micelles consists of aggregation of amphiphilic molecules that contain polar and non-polar moieties, which associate in a manner that minimizes hydrophobic and lipophilic interactions. However, a cascade molecule consisting of an internal lipophilic framework and a external hydrophilic surface would effectively be a unimolecular micelle [59] capable of hosting molecular guest(s). 

Newkome, G.R., Moorefield, C.N., Keith, J.M., Baker, G.R., and Escamilla, G.H. (1994) Chemistry of micelles. 37. Internal chemical transformations in a precursor of a unimolecular micelle boron supercluster via site-specific addition of BioH14 to cascade molecules. Angew. Chem., Int. Ed. Engl. 33, 666-668. 

Szleifer, I., Ben-Shaul, A. and Gelbart, W. M. (1986). Chain statistics in micelles and bilayers effects of surface roughness and internal energy, J. Chem. Phys., 85, 5345-5358. 

Fig. 7 Some peculiar morphologies observed for crew-cut micelles. Baroclinic tubes (a). Tube-walled vesicles (b). Large compound micelles insert shows their internal structure (c) and interconnected tubules or plumber nightmare (d) (images downloaded from http //ottomaass.chem.mcgill.ca/groups/eisenberg/). Adapted from [35]...

Figure 6.5 Illustrations of nanoscale spherical assemblies resulting from block copolymer phase separation in solution are shown, along with the chemical compositions that have been employed to generate each of the nanostructures (a) core crosslinked polymer micelles (b) shell crosslinked polymer micelles (SCKs) with glassy cores (c) SCKs with fluid cores (d) SCKs with crystalline cores (e) nanocages, produced from removal of the core of SCKs (f) SCKs with the crosslinked shell shielded from solution by an additional layer of surface-attached linear polymer chains (g) crosslinked vesicles (h) shaved hollow nanospheres produced from cleavage of the internally and externally attached linear polymer chains from the structure of (g)...

Micelles have internal cavities of the order of 1-3 nm diameter, which allow them to act as nanoscale photochemical reactors for incarcerated guest molecules. Photons absorbed by the guest provide the necessary activation to break covalent bonds in the guest molecule, while the resulting reaction intermediates are themselves constrained to remain in the micelle cavity. 

Micellar systems Internal microviscosity of micelles Fluidity and order parameters (e.g. bilayers of vesicles)... 

Shown in Figure 1 are the principal schemes for micelle and liposome formation and loading with various reporter moieties that might be covalently or noncovalently incorporated into different compartments of these particulate carriers. Although micelles may be loaded with a contrast agent only into the core in the process of micelle assembly, liposomes may incorporate contrast agents in both the internal water compartment and the bilayer membrane. 

Figure 1 Schematic structures of micelle and liposome, their formation and loading with a contrast agent, (a) A micelle is formed spontaneously in aqueous media from an amphiphilic compound (1) that consists of distinct hydrophilic (2) and hydrophobic (3) moieties. Hydrophobic moieties form the micelle core (4). Contrast agent (asterisk gamma- or MR-active metal-loaded chelating group, or heavy element, such as iodine or bromine) can be directly coupled to the hydrophobic moiety within the micelle core (5), or incorporated into the micelle as an individual monomeric (6) or polymeric (7) amphiphilic unit, (b) A liposome can be prepared from individual phospholipid molecules (1) that consists of a bilayered membrane (2) and internal aqueous compartment (3). Contrast agent (asterisk) can be entrapped in the inner water space of the liposome as a soluble entity (4) or incorporated into the liposome membrane as a part of monomeric (5) or polymeric (6) amphiphilic unit (similar to that in case of micelle). Additionally, liposomes can be sterically protected by amphiphilic derivatization with PEG or PEG-like polymer (7) [1].

Polymeric micelles, stars and dendrimers in solution consist of a number of polymer chains that form relatively compact aggregates that exhibit internal dynamics and overall diffusion. Whereas the association of polymer in a micelle is usually driven by physical interactions, the star and dendrimer architecture is generally achieved by chemical bonds. 

This conclusion implies that the excess entropy of mixing is non-zero and that the mixed micelles presumably acquire more internal order than they would by random mixing. An examination of the magnitude of the deviations from the regular solution approximation shows that there must be a large TS contribution to the excess free energy of mixing. 

In addition, Nicolle et al. (Ill) have shown that the mobility of the embedded Gd-complex can be described by two rotational correlation times using the Lipari-Szabo analysis, i.e., a correlation time describing the overall rotational mobility of the micelle and a correlation time for the internal mobility of the Gd-complex inside the micellar structure. 

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