Micelles characterization

Generalities about block copolymer micelles have been reviewed by Ham-ley [2] and Riess [14], based on previous works from the 1980s and 1990s. This topic will not be covered in detail, but the basic principle, as well as some important practical issues, will be reviewed. The essential experimental techniques used for block copolymer micelle characterization will also be outlined briefly. 

Extensive reviews on experimental techniques suitable for block copolymer micelle characterization have been provided by Tuzar [41], Munk [42], Chu and Zhou [19] Webber [43], Mortensen [44], Zana [45], and Hamley [2]. Moreover, Hamley has systematically listed the different techniques specifically used for different types of block copolymer micelles. 

The more recently developed cryo-TEM technique has started to be used with increasing frequency for block copolymer micelle characterization in aqueous solution, as illustrated by the reports of Esselink and coworkers [49], Lam et al. [50], and Talmon et al. [51]. It has the advantage that it allows for direct observation of micelles in a glassy water phase and accordingly determines the characteristic dimensions of both the core and swollen corona provided that a sufficient electronic contrast is observed between these two domains. Very recent studies on core-shell structure in block copolymer micelles as visualized by the cryo-TEM technique have been reported by Talmon et al. [52] and Forster and coworkers [53]. In a very recent investigation, cryo-TEM was used to characterize aqueous micelles from metallosupramolecular copolymers (see Sect. 7.5 for further details) containing PS and PEO blocks. The results were compared to the covalent PS-PEO counterpart [54]. Figure 5 shows a typical cryo-TEM picture of both types of micelles. 

In the experiments described below, FCS measurements were performed for varying concentrations of ORB added to the studied solution of micelles. The obtained autocorrelation curves were fitted to the function, assuming the presence of two types of fluorescent particles (free probe and labeled micelles) characterized... 

The size and shape evolution of reversed micelles as a function of the water and surfactant concentrations are system-specific. The micellar size is mainly controlled by the strong tendency of the surfactant to be located at the interface between water and apolar solvent, which involves an enormous value of the interfacial surface and micelles of nanometric size. Spherical micelles result fl om a minimization of the micellar surface-to-volume ratio, i.e., a minimization of water-surfactant interactions less favorable than water-water and/or surfactant-surfactant interactions, while rodlike micelles, characterized by a greater surface-to-volume ratio, result from water-surfactant interactions more favorable than... 

Tian, H.Y., Deng, C., Lin, H., Sun, J., Deng, M., Chen, X. and Jing, X. (2005) Biodqpadable cationic PEG-PEl-PBLG hyperbranched block copolymer synthesis and micelle characterization. Biomaterials, 26,4209-4217. 

More recently, additional studies involving the use of GPC in micelle characterization have been reported.From GPC studies carried out on poly(oxyethylene) n-alkyl ethers in aqueous media,it has been shown using a model proposed by Coll that the position and width (after correction for instrumental spreading) of the elution peak for micelles is not influenced by micelle dissociation provided the critical micelle concentration (cmc) is very low compared with the concentration of the solution injected into the columns. 

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