Micelle of amphiphilic block copolymers

In the second approach, metal-ion/complex was first attached to one of the polymer blocks. A thin film of the resulting polymer metal complex was then obtained by spin coating/solution casting. Alternatively, the polymer metal complex may also be dissolved in a suitable solvent system that selectively dissolves one of the blocks. Micelles or nanosized aggregates formed in this case. The micellization of amphiphilic block copolymers and their use in the formation of metal nanoparticles has been discussed previously.44 A monolayer of micelles was introduced on a substrate surface by dipping or electrostatic attraction. The substrate was then subjected to further chemical or physical treatments as mentioned earlier. The third approach involves the formation of micelles from the metal-free block copolymer in a suitable solvent system. The micelle solution was then added with metal ion, which was selectively coordinated to one of the blocks. These micelle-metal complexes can also be processed by a procedures similar to the second approach. 

Kabanov AV, Alakhov VY. Micelles of amphiphilic block copolymers as vehicles for drug delivery. In Alexandridis P, Lindman B, eds. Amphiphilic Block Copolymers Self Assembly and Applications. Netherlands Elsevier, 1997 1-31. 

Kataoka, K., Design of nanoscopic vehicles for drug targeting based on micellization of amphiphilic block copolymers. Pure Appl. Chem., 11, 1759-1769 (1994). 

The dynamics of micelles of amphiphilic block copolymers (macromolecular surfactants) of even relatively small size is reviewed in Chapter 4. 

Kim, J.M., Sakamoto, Y., Hwang, Y.K., Kwon, Y.U., Terasaki, O., Park, S.E. and Stucky, G.D. (2002) Structural design of mesoporous silica by micelle-packing control using blends of amphiphilic block copolymers. Journal of Physical Chemistry B, 106, 2552— 2558. 

Letchford K, Burt H (2007) A review of the formation and classification of amphiphilic block copolymer nanoparticulate structures micelles, nanospheres, nanocapsules and polymersomes. Eur J Pharm Biopharm 65 259-269... 

Application of amphiphilic block copolymers for nanoparticle formation has been developed by several research groups. R. Schrock et al. prepared nanoparticles in segregated block copolymers in the sohd state [39] A. Eisenberg et al. used ionomer block copolymers and prepared semiconductor particles (PdS, CdS) [40] M. Moller et al. studied gold colloidals in thin films of block copolymers [41]. M. Antonietti et al. studied noble metal nanoparticle stabilized in block copolymer micelles for the purpose of catalysis [36]. Initial studies were focused on the use of poly(styrene)-folock-poly(4-vinylpyridine) (PS-b-P4VP) copolymers prepared by anionic polymerization and its application for noble metal colloid formation and stabilization in solvents such as toluene, THF or cyclohexane (Fig. 6.4) [42]. 

Sha et al. applied the commercially available dual initiator ATRP-4 for the chemoenzymatic synthesis of block copolymers. In a first series of publications, the group reported the successful synthesis of a block copolymer comprising PCL and polystyrene (PS) blocks [31, 32]. This concept was then further applied for the chemoenzymatic synthesis of amphiphilic block copolymers by macroinitiation of glycidyl methacrylate (GMA) from the ATRP functional PCL [33]. This procedure yielded well-defined block copolymers, which formed micelles in aqueous solution. Sha et al. were also the first to apply the dual enzyme/ATRP initiator concept to an enzymatic polycondensation of 10-hydroxydecanoic acid [34]. This concept was then extended to the ATRP of GMA and the formation of vesicles from the corresponding block copolymer [35]. 

Au NPs have been synthesized in polymeric micelles composed of amphiphilic block copolymers. Poly(styrene)-block-poly(2-vinylpyridine) in toluene has been used as nanocompartments loaded with a defined amount of HAuCl4 and reduced with anhydrous hydrazine. The metal ions can be reduced in such a way that exactly one Au NP is formed in each micelle, where each particle is of equal size between 1 and 15 nm [113]. In another example, the addition of HAuCfi to the triblock copolymer (PS-b-P2VP-b-PEO) (polystyrene-block-poly-2-vinyl pyridine-block-polyethylene oxide) permits the synthesis of Au N Ps using two different routes, such as the reduction of AuC14 by electron irradiation during observation or by addition of an excess of aqueous NaBH4 solution [114]. 

Another of the most fascinating properties of block copolymers is their ability to self-assemble into micelles, aggregates, and vesicles of various morphologies in the presence of a selective solvent, [117,118] and recent studies have demonstrated that self- assemble of amphiphilic block copolymers into various morphologies occurs not only in selective solvents but also at interfaces and surfaces [119,120],... 

So far, micelles and vesicles of amphiphilic block copolymers with two different blocks have been described. In this section the work on amphiphilic block copolymers and block copolyampholytes composed of three different blocks will be reviewed. Much less work has been carried out on these systems and there are less systematic studies available. Focus will be laid on block copolymers with at least one polyelectrolyte block. While in the case of amphiphilic diblock copolymers questions like the influence of block lengths on the size of micellar aggregates have been studied in great detail, in ternary block copolyampholytes other properties have attracted greater interest, such as the influence of the block sequence on the solution properties and aggregate formation. 

Polymer micelles are supramolecular assemblies of amphiphilic block copolymers that have a characteristic... 

J.M. Kim, Y. Sakamoto, Y.K. Hwang, Y.U. Kwon, O. Terasaki, S.E. Park, and G.D. Stucky, Structural Design of Mesoporous Silica by Micelle-packing Control using Blends of Amphiphilic Block Copolymers, J. Phys. Chem. B, 2002, 106, 2552-2558. 

Fig. 10.2 Nanoparticles formed via polymer micelles by self-assembly of amphiphilic block copolymers...

The research on microemulsions currently concentrates on even more complex mixtures. By adding amphiphilic macromolecules the properties of microemulsions can be influenced quite significantly (see Chapter 4). If only small amounts of amphiphilic block copolymers are added to a bicontinuous microemulsion a dramatic enhancement of the solubilisation efficiency is found [27,28]. On the other hand, the addition of hydrophobically modified (HM) polymers to droplet microemulsions leads to a bridging of swollen micelles and an increase of the low shear viscosity by several orders of magnitude [29]. 

Energy-transfer measurements have also provided an insight into the structure of amphiphilic block copolymer micelles with hydrophobically modified polyelectrolyte shells [172]. 

Polymeric micelles, which were first introduced by Ringsdorf in 1984 [14], are an assembly of amphiphilic block copolymers in an aqueous environment. Primary polymeric micelles have a well-defined core-shell structure - a hydrophobic inner core and a hydrophilic shell. Micelles can incorporate water-insoluble drugs into the cores through chemical, physical, or electrostatic interactions [15], such as in micelles that are composed of a block copolymer of poly(ethylene glycol) and polyaspartate (Fig. 2) [16-18], A phase II study of a paclitaxel (PTX)-incorporated micelle, NK105, that is used in the treatment of stomach cancer, has begun [19]. 

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