Micelles metallosupramolecular

Recent progress in novel micellar structures, including micelles containing exotic blocks such as natural or synthetic polypeptides and metal-containing segments, micelles from ABC triblock copolymers, Janus micelles and other noncentrosymmetric micelles, micelles based on interpolyelectrolyte or other noncovalent complexes, and metallosupramolecular micelles, will be discussed in Sect. 7. 

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. 

Fig. 4 Pt-shadowed TEM picture of micelles and aggregates formed by metallosupramolecular PS2o-[Ru]-PE07o aqueous micelles. Reprinted with permission from [48]. Copyright (2003) Wiley...

Fig.5 Cryo-TEM pictures of metallosupramolecular PS2o-[Ru]-PEC>7o (a) and covalent PS22-PEO70 (b) aqueous micelles. Arrows in a indicate isolated micelle and cluster of micelles. Reprinted with permission from [54]. Copyright (2004) Springer... 

In a very recent set of papers [48,54,59,60,131,132,324-328], the synthesis and characterization of metallosupramolecular amphiphilic block copolymers containing a hydrophilic PEO block linked to a hydrophobic PS or PEB block through a fozs-2,2/ 6/,2/terpyridine-ruthenium(II) complex have been described. These copolymers form the so-called metallosupramolecular micelles . 

TEM observations successfully demonstrated that the large aggregates resulted from clustering of individual micelles for the metallosupramolecular micelles [54]. 

Clustering in PS-[Ru]-PEO micelles was shown to be sensitive to temperature and ionic strength, as previously observed for covalent PS-PEO copolymer [131]. These effects were, however, more pronounced in the case of the metallosupramolecular copolymers, indicating a possible influence of the charged fois-2,2/ 6/,2/terpyridine-ruthenium(II) complexes [329]. 

Fig.24 TEM picture of cylindrical micelles formed by a PFSi2-[Ru]-PEC>7o metallosupramolecular copolymer in water. No contrasting agent has been added for visualization of these micelles because they contain iron atoms in the core. Reprinted with permission from [331]. Copyright (2004) Wiley...

Covalent and metallosupramolecular block copolymers have been combined in a single macromolecular structure. In this respect a terpyridine-functionalized PS-P2 VP has been complexed with a terpyridine-functionalized PEO, leading to a PS32-P2VPi3-[Ru]-PE07o ABC triblock copolymer [330]. This copolymer was further used to prepare core-shell-corona micelles consisting of a PS core, a pH-responsive P2VP shell, and a PEO corona. 

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