Chemistry Reference
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Figure 11.21 (a) Structure and (b) self-assembly of conelike amphiphilic glutamic acid-
dendritic diblock hybrids.
These “rodcoil” dendrons assemble in the solid state, under hydrating conditions,
into aggregates composed of a lamellar bilayer of cholesterol molecules surrounded
by a shell of
L
-lysine dendrons. The
L
-lysine dendrons become more sterically
demanding as the level of hydration is increased, which destabilizes the lamellar
organization. This increased steric bulk is not sufficiently destabilizing at the first
and second generations; however, the third-generation dendrons preclude formation
of the bilayer in favor of nanosized aggregates. In a series of PS-PPI copolymers,
Meijer found that the aggregate morphology similarly followed the theory of
Israelachvilli and coworkers (1977, 1980) as the dendritic head group increased in
size (van Hest, Baars, et al. 1995; van Hest, Delnoye, et al. 1995; van hest,
Delnoye, et al. 1996). As the head group increased in size going from PS-dendr-
(NH
2
)
8
and PS-dendr-(NH
2
)
16
to PS-dendr-(NH
2
)
32
,
the aggregate morphology
transitioned from vesicular structures and micellar
rods to spherical micelles
(Fig. 11.23).
Based on Israelachvilli's predictions, Kellermann et al. (2004) designed a cone-
shaped dendro-calixarene molecule displaying two polar carboxylate-terminated
G2 dendrons on one face and four C
12
chains extending from the opposite face
(Fig. 11.24).
Remarkably, a highly uniform and highly stable micellar aggregate of exactly
seven molecules was
formed in water. Although these aggregates
resisted
