Dendritic unimolecular micelle

Recently, we are also able to perform liquid-liquid extractions of water-soluble dyes from water to organic solvents like toluene using the unimolecular dendritic micelles as extractants. These guest-host properties of the modified poly(propylene imine) dendrimers make use of the basic nature of the interior of the dendrimer. Therefore, it is possible to transfer dyes like Bengal Rose into toluene. Although simple tri-octylamines are capable of transferring these dyes as well, it is evident from the experiments that unimolecular dendritic inverted micelles are much more selective, probably due to the shielding effect of the apolar shell [70]. 

It is also of interest to study the self-assembly of these inverted unimolecular dendritic micelles into vesicles in water at pH = 1 and at the air-water interface. In these vesicles, the dendrimers adopt a distorted conformation, far from spherical. These dendritic amphiphiles form a novel class of vesicle-forming surfactants [71] and introduce new perspectives towards a better understanding of the structure-property relation of amphiphiles on the one hand and dendrimers on the other hand. 

Figure 23 Schematic representation of the vesicle formation of the fifth generation inverted unimolecular dendritic micelles...

Stevelmans S, vanHest JCM, Jansen J et al (1996) Synthesis, cheu cterization, and guest-host properties of inverted unimolecular dendritic micelles. J Am Chem Soc 118 7398-7399... 

Piotti ME, Rivera F Jr, Bond R, Hawker CJ, Frechet JMJ. Synthesis and catalytic activity of unimolecular dendritic reverse micelles with internal functional groups. J Am Chem Soc 1999 121 9471-9472. 

Fig. 5 Water soluble unimolecular dendritic polyether micelle. (From Ref. " 1993 Royal Society of Chemistry.)...

Meanwhile, other examples of unimolecular dendritic, inverse micelles have been reported by Meijer et al. [158] and DeSimone et al. [159]. In the latter case, surface perfluorinated dendri-PPl dendrimers were used, which have a high affinity for liquid CO2. Thus, the hydrophilic dendrimer core provides a favorable environment for hydrophilic guests such as ionic methyl orange. Thus while... 

More recently Frechet and Gitsov [130] used a similar approach as above and synthesized a novel series of dendritic copolymers derived from a central penta-erythritol core unit. These hybrid star molecules behaved as unimolecular micelles with different core-shell conformational-structures as a response to the polarity of the solvent used. 

C. J. Hawker, K. L. Wooley, and J. M. J. Frechet, Unimolecular micelles and globular amphiphiles Dendritic macromolecules as novel recyclable solubilization agents, J. Chem. Soc. Perkin Trans. 1, 12 (1993) 1287-1297. 

Liu, M., Kono, K., and Frechet, J.M.J. (2000) Water-soluble dendritic unimolecular micelles their potential as drug delivery agents./. Contr. Release 65, 121-131. 

In this section the emphasis will be on assemblies prepared from amphiphilic dendrimers. Amphiphilic dendrimers, carrying both hydrophobic and hydrophilic regions within one molecule, tend to self-assemble into a large variety of different aggregates depending on their structure. The dendritic amphiphiles investigated so far include unimolecular micelles, bolaamphiphiles, superam-phiphiles and various other AB and ABA block copolymers. 

Unimolecular micelles are defined as a class of dendritic macromolecules, wherein an interior hydrophobic core is surrounded by a hydrophilic surface layer. These structures closely resemble the shape of classical micelles (shape,... 

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