Micelles and micellization

Dou H, Jiang M, Peng H et al (2003) pH-dependent self-assembly micellization and micelle-hollow-sphere transition of cellulose-based copolymers. Angew Chem Int Ed 42 1516-1519... 

DR. JOHN MALIN (National Science Foundation) I know that people have been worried about the dynamics of micelles and micelle formation and have studied these processes by NMR. I am wondering what the results of those studies have been. Without belaboring this point, do you know the residence time of a surfactant molecule in a given micelle before it transfers to a neighbor, or whether they fuse and come apart again ... 

Fig. 6.3 Different types of micelles and micelle analogous structures a) amphiphilic block copolymers, b) star-like polymers with a hyperbranched core, c) polysoaps.

Payens, T. A. J. and Vreeman, H. J. 1982. Casein micelles and micelles of k- and 0-casein. In Solution Behavior of Surfactants, Vol. I. K.L. Mittal and E.J. Fendler (Editors). Plenum Publishing Corp., New York. 

Figure 2.7 shows that with increase in the degree of epoxy conversion, pre-associations occur at lower surfactant concentrations. The siu -factant concentration at which pre-micelles and micelles are formed is related to the decline of surfactant solubility in the oligomer during its polymerization. 

One of the rare works on the kinetics of the formation of mixed micelles of Pluronics and surfactants also treats the system L64/SDS [58]. In temperature-jump experiments, the authors identified three different relaxation times for the L64/SDS mixture. The fastest ps) is associated with the binding of additional L64 unimers to the micelles. The two slower relaxation processes are interpreted as structural rearrangement of the mixed micelles and micelle clustering. These findings are qualitatively in agreement with the first kinetic investigation of these mixtures by Hecht and Hoffmann [59]. 

Jain, N.J., Aswal, V.K., Goyal, P.S. and Bahadur, P. (2000) Salt induced micellization and micelle structures of PEO/PPO/PEO block copolymers in aqueous solution. Colloid. Surf. A, 173(1-3), 85-94. 

De Schryver et al. [44] applied this model to analyse the pyrene fluorescence quenching by metal ions in SDS micelles. The situation described by the inequality (40) was observed for nickel, copper and lead ions. The values were determined from the slope of the linear plot of S2/SS vs. [M] [see Eq. (43)]. For europium and chromium ions, both interfacial exchange processes in micelle-micelle and micelle-bulk solution are very slow as compared with pyrene fluorescence decay. Here, the kinetics fits well to Case 2 discussed above. For silver and thallium ions, the rates of the fluorescence... 

Najaragan [25] has introduced a comprehensive thermodynamic treatment of surfactant/polymer interaction. The aqueous solution of surfactant and polymer was assumed to contain both free micelles and micelles bound to the polymer molecule. The total surfactant concentration, Xt, is partitioned into single dispersed surfactant, Xi, surfactant in free micelles, Xf, and surfactant bound as aggregates, Xb,... 

The adsorption of many surfactants at the solid/liquid interface may show several steps that are accompanied by various structures on the surface (bilayers, hemi-micelles and micelles). This is represented in detail in Chapter 4. 

III. KINETIC STUDIES OF THE VESICLE-TO-MICELLE AND MICELLE-TO-VESICLE TRANSFORMATIONS... 

Although the classical picture of a micelle is that of a sphere, most evidence indicates that spherical micelles are not the rule and may in fact be the exception. As a result of geometric packing requirements and analyses (to be discussed below), ellipsoidal, disk-shaped, and rodUke structures may be the more commonly encountered shapes. However, from the standpoint of providing a concept of micelles and micelle formation for the nonspeciaUst, the Hartley spherical model remains a useful and meaningfiil tool. 

---