Chemistry Reference
In-Depth Information
13.2. DENDRIMERS TO GLYCODENDRIMERS
Dendrimers are macromolecules that have a series of branches emanating from a central
core. They can be synthesized starting from the core and working out toward the periph-
ery (divergent synthesis). Alternatively, dendrimers can be formed in a top-down
approach starting from the outermost residues (convergent synthesis; Fr´chet and
Tomalia 2001; Newkome et al. 2001). Because dendrimers are built from AB
n
-type
monomers, each layer or “generation” of branching units doubles or triples (n ¼ 2
or 3) the number of peripheral functional groups. The poly(amido amine) (PAMAM)
dendrimer is a commercially available framework with highly flexible branches
(Fig. 13.5). Tertiary amine units at the branch points result in a doubling of the
number of termini for every successive PAMAM generation (Tomalia et al. 1986).
Other dendrimer frameworks have also been widely publicized. Poly(propylene
imine) (PPI) dendrimers are like PAMAMs except that no amides are present in
their structures. Tertiary amines serve as branch points and primary amines serve
as termini for traditional PPI dendrimers (Buhleier et al. 1978; de Brabander-van
den Berg and Meijer 1993). The PPI framework is shown in Figure 13.6. Note that
PAMAM dendrimers are named using G(0) to describe the species bearing four
end groups, but PPI dendrimer nomenclature dictates that a G(1) dendrimer has
four end groups. Thus, the G(3) PPI dendrimer shown in Figure 13.6 has the same
number of end groups as the G(2) PAMAM shown below.
Figure 13.5 The structure of the G(2)-poly(amido amine) dendrimer.
