Dendritic unimolecular micelle system

For a general review on supramolecular chemistry with dendrimers, the reader is referred to an excellent paper of Zimmerman et al. [18]. Because of our acquaintance with the polylpropylene imine) dendrimers, we will restrict ourselves in this Chapter to some examples of supramolecular behaviour of these systems as investigated in our laboratory. Three systems will be discussed (Figure 1) the dendritic box, which can encapsulate guest molecules, the polystyrene-poly(propy-lene imine) block copolymer superamphiphiles, and alkyl-decorated dendrimers, which function as unimolecular micelles, and show surprising aggregation behaviour. However, first the synthesis and properties of the poly(propylene imine) dendrimers will be discussed to demonstrate some typical dendrimer features. 

PAMAM dendrimers, synthesized subsequently, are likely the most widely investigated and used dendritic polymers to date. The first dendrimers commercialized in that family were the Starburst systems. These species were developed in the mid-1980s by Tomalia [5], at about the same time when Newkome developed similar dendritic architectures named Arborols [6]. A major incentive for the development of these molecules was the creation of covalently bonded (unimolecular) micelles comparable to the well-known multi- or intermolecular micellar systems. 

Hyperbranched polymers have been used to make unimolecular micelles and novel liquid crystals (see below for a discussion of liquid crystals). A major advantage of hyperbranched systems is that their synthesis is a single step It seems likely that for some applications, hyperbranched systems will perform well, but for others, the precision of a dendritic system will be required. 

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