Dendrimer synthesis

HPLC is limited to relatively low molar mass compounds, Le. below 3000. In practice this tends to restrict the technique to dendrons rather than fully formed dendrimers, but it is nonetheless a useful technique, given the importance of establishing high analytical purity of products at each step in a dendrimer synthesis. 

A dendrimer-based approach for the design of globular protein mimics using glutamic (Glu) and aspartic (Asp) acids as building blocks has been developed [151]. The preassembled Glu/Asp dendrones were attached to a 1,3-bifunctional adamantyl based on a convergent dendrimer synthesis strategy (see Fig. 28). 

Fig. 2a-c. Dendrimer synthesis using linear building blocks a Vogtle s original procedure b DSM s commercial process c Tomalia s synthesis of PAMAM dendrimers... 

Fig. 3i-iii. Dendrimer synthesis using branched building blocks i Denkewalter s polylysine dendrimers ii Newkome s polyamide dendrimers iii Frechet s aryl ether dendrimers... 

Each step in dendrimer synthesis occurs independent of the other steps therefore, a dendrimer can take on the characteristics defined by the chemical properties of the monomers used to construct it. Dendrimers thus can have almost limitless properties depending on the methods and materials used for their synthesis. Characteristics can include hydrophilic or hydrophobic regions, the presence of functional groups or reactive groups, metal chelating properties, core/shell dissimilarity, electrical conductivity, hemispherical divergence, biospecific affinity, photoactivity, or the dendrimers can be selectively cleavable at particular points within their structure. 

Swali, V., Wells, N.J., Langley, G.J., and Bradley, M. (1997) Solid-phase dendrimer synthesis and the generation of super-high-loading resin beads for combinatorial chemistry. J. Org. Chem. 62, 4902-4903. 

The robustness and excellent turnover numbers of platinum complexes with terminal alkynes have made it the catalyst of choice for the synthesis of polymers and other macromolecular architechtures. Alkyne hydrosilylation with platinum has also served as a key element in the synthesis of dendrimers. Sequential reaction of an alkyne with HSiMeCl2 and lithiated phenylacetylene afforded the branching unit of a dendrimer synthesis which has been used to afford a large variety of structures at high generation.44,4411 441 ... 

Dendrimer architectures are largely determined by the types of branching units they display. To be realised in a dendrimer synthesis, these branching units have to fulfil certain conditions. 

Figure 8. Doubly exponential dendrimer synthesis involving simultaneous growth in divergent and convergent directions.

Way (3) (Figure 12) also leads to polyfunctional-ized molecules. In most cases, it involves a considerable synthetic effort, since it is necessary to synthesize the whole dendrimer skeleton de novo. Moreover, the functionalities which are introduced have to tolerate the often quite drastic reaction conditions of the dendrimer synthesis. The advantage of... 

Conventional sulfur vulcanization cure systems, 21 801 Convention du Mtre, 24 434 Convergent dendrimer synthesis method, 26 787-788... 

Dendrimer synthesis, 26 787-788 breakthrough approaches in, 26 788 Dendritic box, 26 790 Dendritic metallic silver, 19 367—368 Dendritic nanoparticles, water-soluble, 26 796... 

Mathematically, the number of covalent bonds formed per generation (reaction step) in an ideal dendron or dendrimer synthesis varies according to a power... 

Another example of hypermonomer-based dendrimer synthesis was reported by Gilat et al. for the rapid preparation of a new family of laser dye-labeled dendrimers that were critical to our study of energy transfer in light harvesting dendrimers (Scheme 6) [29]. In order to avoid undesirable through-bond energy transfer in the poly(benzyl ether dendrimers, the reversed monomer unit,... 

The convergent approach to dendrimer synthesis has evolved considerably over the past dozen years. With the benefit of hindsight, it is clear that the key criteria for a successful convergent synthesis include ... 

The authors thank the National Science Foundation (DMR) for the continued support of research in the field of dendrimer synthesis. Additional support by the ARO (MURI program) is also acknowledged with thanks. 

Meijer and co-workers also used a divergent dendrimer synthesis to prepare AB diblock structures (Figure 7.13B) in which the polystyrene linear block is used to initiate growth of the polypropylene imine) dendritic block [45], An amino end group had to be introduced in the polystyrene as a core for subsequent growth of the dendritic fragment via an iterative protocol of sequential... 

Dendrimer synthesis involves a repetitive building of generations through alternating chemistry steps which approximately double the mass and surface functionality with every generation as discussed earlier [1-4, 18], Random (statistical) hyperbranched polymer synthesis involves the self-condensation of multifunctional monomers, usually in a one-pot single series of covalent formation events [31], Random hyperbranched polymers and dendrimers of comparable molecular mass have the same number of branch points and terminal units, and any application requiring only these two characteristics could be satisfied by either architectural type. Since dendrimer synthesis requires many defined synthetic and process purification steps while hyperbranched synthesis may involve a one-pot synthetic step with no purification, the dendrimers will necessarily be a much more expensive material to produce. 

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