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formed uniformly monomeric particles (30+10
˚
; Newkome et al. 1991). Indeed,
their fluorescence studies indicated that these dendrimers maintained a lipophilic
internal environment capable of binding hydrophobic probes with an apparent
CMC of ,3.9
10
27
M (Fig. 11.3b; Newkome, Moorefield, Baker, Saunders,
et al. 1991).
Poly(amido amine) (PAMAM) Dendrimers.
These dendrimers have a hydro-
philic polyamide interior that is relatively open to solvent, in contrast to a micellar
assembly. Yet, the picture of a unimolecular micelle also emerged for a generation
4.5 PAMAM dendrimers having sodium carboxylate terminal groups (Fig. 11.4).
Individual molecules of this dendrimer could actually be observed by electron
microscopy as spheroid particles having a diameter of 88+10
˚
, comparing favor-
ably with a predicted diameter of 78
˚
for a single, fully extended dendrimer structure
(Tomalia et al. 1987). The similarity of the surface of these dendrimers to anionic
Figure 11.4 Generation 4.5 poly(amido amine) dendrimer having sodium carboxylate
terminal groups.
