Hyperbranched dendritic moiety

Dendritic macromolecules are hyperbranched fractal-like structures that emanate from a central core and contain a large number of terminal groups. Two synthetic approaches have been reported for the preparation of these macromolecules the divergent [76-78] and convergent growth approaches [79-82]. In both methods many synthetic steps are necessary to produce high molecular weight materials. To avoid synthetic problems, the macromonomer with hyperbranched dendritic moiety may be one of the most useftil materials for the dendritic macromolecules. 

Dendritic macromolecules exhibit compact globular structures which lead to their low viscosity in the melt or in solution. Furthermore, dendritic macromolecules are characterized by a very large number of available functional groups, which lead to unprecedented freedom for changing/tuning/tailoring the properties of these multivalent scaffolds via complete or partial derivatization with other chemical moieties. All these features have contributed to multidisciplinary applications of these unique macromolecular structures in recent years 6, 7). The development of efficient synthetic routes in recent years has given rise to a virtually unlimited supply of commercially available dendritic polymers, at very affordable price. The transport properties of hyperbranched and dendritic polymers have recently attracted attention as potentially new barrier and membrane materials 8-9). 

Some selected examples of hyperbranched polymer-supported catalysis are summarised in Table 4. Dendritic carbosilane structures are well suited for catalysis because they are relatively inert to common organometaUic reagents and their structures can be easily modified. For example, Frey and van Koten reported on the synthesis of a hyperbranched carbosilane, its fmctionaUsation with NCN moieties and the introduction of paUadium(II) sites into the structure [ 82 ]. This catalyst was introduced in aldol reactions and showed similar activity as the low molecular analogue. 

Polymer Factory Sweden AB (PF) (http //www.polymerfaaory. com and subpages thereof, accessed 8 July 2010) is a manufacturer and provider of PBisMPA dendrons, dendrimers, and hyperbranched materials comprising a range of different end-group funaionalities and focal point moieties. The company has today the widest dendritic library available on the... 

Hyperbranched polymers containing an encapsulated single core moiety have qualified as an interesting alternative to den-drimers for analogous studies, since they resemble in a majority of their characteristics and are usually easily accessible by a convenient synthesis. Tian et al. used a modified triphenyla-mine as core for a conjugated hyperbranched polymer, where a direct influence of the hyperbranched architecture on UV-absorption and fluorescence properties of the core was observed. Furthermore, postpolymerization modification of the nitrophenyl ester core, subsequent to the formation of the dendritic structure, has been reported. 

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