Functional groups divergent

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. 

Dendritic growth hybrids are prepared using one or more functional groups of a preformed linear chain to effect the stepwise growth of one or more dendritic blocks via divergent synthesis. 

In the divergent method (Fig. 4), the molecule is assembled from the core to the periphery, while in the convergent method, the molecule is synthesized from the periphery to the core. In either method, the synthesis requires a stepwise process, attaching each layer to the previous one, purifying and then changing functional groups for the next stage of reaction. 

The dendrimer is a new type of cross-linked nanoparticle prepared by repetitive reactions to compose dendritic structure. There are two kinds of preparative methods, divergent (30) and convergent (31) methods, as shown in Figure 12.2.7. The dendrimer by the former method is constructed from the center of sphere to the outer layers, and therefore the surface chemistry is decided by the final reaction. When a dendrimer is formed from a central ammonia molecule, the forth-generation dendrimer of about 3 nm diameter has 48 functional groups at the surface. If a crowd of functional groups is not desirable on the outermost layer, they can be thinned down properly by replacing a two-functionality compound with a one-functionality one. 

Fig. 2.1 Divergent synthesis. C=coupling points F=active, unprotected functional group P= protected, inactive (protective group) functionality. The core of the dendri-...

Fig. 2.8 Divergent synthesis of dendritic molecules on a solid phase (C=coupling group, F= functional group P= protective group)...

Fig. 2. Retro synthetic analysis for the dendritic structures FG, FP and X, Y are respectively interconvertible functional groups Path A is the divergent synthesis Path B is the convergent synthesis stands for the core structure Q stands for the branching repeat unit...

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