Micellar characteristics

Although it strongly influences the micellar characteristic features, the method used for the preparation of block copolymer micelles has been very often poorly discussed in the literature. This crucial point was raised in the excellent review of Riess [14]. 

Liu and coworkers systematically used photo-cross-linking to stabilize micelles containing a PCEMA core [82]. The micellar characteristic features (Z, etc.) were not affected by the cross-linking process, as proven by SLS, DLS, TEM, and SEC. 

Semianalytical mean-field theories of block copolymer micellization were formulated by Noolandi et al. [ 197] and by Leibler et al. [198]. In the approach of Noolandi et al., the micellar characteristics were obtained through a minimization of the Gibbs free energy for an isolated micelle. This was applied to PS-PB micelles, and the obtained theoretical values were in good agreement with the experimental ones. 

Tabic 3.5 Predictions of Zhulina and Birshtein (1985) for micellar characteristics in an AB diblock in a solvent selective for the A block"... 

The unimolecular micellar characteristics of this poly(ammonium carboxylate) 156 were demonstrated 179 by UV analysis of guest molecules, such as pinacyanol chloride, phenol blue, and naphthalene combined with fluorescence lifetime decay experiments employing diphenylhexatriene as a molecular probe. The monodispersity, or absence of intermolecular aggregation, and molecular size were determined by electron microscopy. 

PEO formed a surface while the hydrophobic carbosilane dendritic block was incorporated into the micelle core. Micellar characteristics were determined using fluorescence techniques and dynamic light scattering. Copolymers with a third-generation dendritic block could not be dispersed in water. 

Desai, H., et al. (2006), Micellar characteristics of diblock polyacrylate-polyethylene oxide copolymers in aqueous media, Eur. Polym. J., 42(3), 593-601. 

Table IV. Micellar Characteristics of Carboxy Terminated Polyesters Micelles Prepared by an Industrial Procedure...

Nam, Y. S. Kang, H. S. Park, J. Y. Park, T. G. Han, S.-H. Chang, I.-S. New micelle-like polymer aggregates made from PEl-PLGA diblock copolymers micellar characteristics and cellular uptake. Biomateiials 2003, 24, 2053-2059. 

Since the micellar characteristics of the PEO-b-P2VP-Pd block copolymer aggregates in a given solvent and at a given pH may influence the catalytic properties, this was another important variable for the present system. PEO-fe-P2VP forms micelles in water whose characteristics are mainly preserved after metallation (incorporation of a metal salt and metal nanoparticle formation) [49], but the behavior of this system in the presence of isopropanol is more complicated. To clarify the effect of solvent composition and pH on micellar characteristics, TEM and atomic force microscopy (AFM) studies of the key reaction mixtures were performed. Table 3.2 summarizes the catalytic data and mean diameters of the micelles and micellar aggregates obtained from AEM. 

SHI Shirai, S. and Einaga, Y., Wormlike micelles of polyoxyethylene dodecyl Ci2Ej and heptaoxyethylene alkyl QE ethers. Hydrophobic and hydrophihc chain length dependence of the micellar characteristics, Polym. J., 37, 913, 2005. 

The various micellar characteristics as mentioned in literature will not be treated here, and the reader is suggested to review the literature for these properties [1,5,6,7,81. However, here only those characteristics which are considered as necessary for the understanding of the chromatographic analyses of micellar systems will be described in detail. 

Amphiphilic block copolymers are well-known starting points for the preparation of micelles—either organized structures in the solid state or individual spherical or worm-like micelles suspended in a liquid medium. In polyphosphazene science, it is relatively easy to prepare diblock copolymers. As discussed above, both blocks can be phosphazenes or one can be a phosphazene and the other an organic polymer block or a poly(organosiloxane). Provided one block is hydrophilic and the other hydrophobic, micellar characteristics (Figure 1.15) are accessible. One example... 

This section is therefore organized as follows after a recall of the typical micellar characteristics, of the various preparation and characterization techniques, the micellization behavior of the different copolymer types, for example non-ionic, anionic and cationic types in aqueous medium will be outlined. This part will mostly be devoted to block copolymers as their structures are in general better defined than for graft copolymers. 

Minimization of this equation with respect to parameters characterizing the micelle leads to correlations between the copolymer and the micellar characteristics. 

In the most recent ones. Booth and co-workers [79, 148] outlined the correlations between the molecular characteristics (composition, structure, molecular weight) and the corresponding micellar characteristics, such as the CMC and GMT, the micellization enthalpy, the micelle size and association number, etc. These characteristic features were studied by SLS, DLS, SAXS, SANS, NMR, etc. 

A typical example of the polyelectrolyte effect of quaternized PS-P4VP copolymers was reported by Calderara [126] and Riess and Hurtrez [129], The P4VP block is soluble in methanol, whereas the corresponding quaternized block PQ4VP, obtained with methyl iodide, is soluble in water. The micellar characteristics of a diblock copolymer with Nps= 154... 

Table 7.5 Micellar characteristic of PS154-P4VP381 and of the corresponding quaternized PS-P4VP 1 ...

The micellar characteristics as determined by DLS and viscometry in aqueous medium are summarized in Table 7.8. 

Table 7.8 Micellar characteristics of PB-P2VP-PEO triblock copolymers in water at 20°C ...

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