142 Advances in Polymer Science Editorial Board: A. Abe. A.-C ...

182 J. Roovers, B. Comanita
Fig. 1a–c. Schematic representation of the different parts of a dendrimer; –< stands for the
repeat branching unit (monomer); X are end-standing (terminal) functional groups; Y is
the functional group of the focal point: a core or focal point; b generation one dendrimer or
dendron; c generation two homologues. The branching functionality of the core is four
while the branching functionality of the monomer is three
is not necessarily the physical center of the dendrimer nor are the end groups
necessarily permanently located at the periphery of the dendrimer.
The steady branching pattern of the dendrimer architecture is paralleled by
an exponential increase of the molecular mass with each successively added generation.
Dendrimers with more than a few generations have molecular weights
that resemble those of step-growth polymers (10 4 –10 5 D). For that reason and
for the presence of an identifiable (branched) repeat unit, higher generation
dendrimers are considered polymeric molecules.
1.2
Synthetic Highlights
Retrosynthetic analysis [1] of the generic dendritic structure (1) suggests two
possible solutions for the synthesis of dendrimers (see Fig. 2). A first disconnection
along Path A leads to generation n-1 dendrimer (2) and the branching monomer
synthon (3). This rationale can be successively applied until the problem
is reduced to the reaction of a core synthetic equivalent (4) with the branching
monomer (3). Alternatively, along Path B, synthon (4) can react with the
branched dendron (5) to provide the target dendrimer (1). After further iterative