Chemistry Reference
In-Depth Information
CO
2
Me
MeO
2
C
MeO
2
C
CO
2
Me
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
MeO
2
C
CO
2
Me
O
O
O
O
O
O
O
O
O
O
O
O
O
O
OO
OO
O
O
O
O
n
n
FIGURE 4.11
Chemical structures of crown ether-based dendronized polymers
PG1
and
PG2
from macromonomer route.
decharging of the polymers with ions can be exploited for inducing shape changes of
macroscopic materials like films prepared from these polymers [35]. Whether there
are any thickness effects is too early to speculate about.
4.4 HELICAL DENDRONIZED POLYMERS
Having spatially rather demanding substituents bonded in tight distance to a linear
polymer backbone raises the question whether this unique situation could be used to
create dendronized polymers with a predetermined helical screw sense. The dense
packing of the (dendritic) substituents may result in novel helical polymers exhibiting
unprecedentedly stable helical conformations over a wide temperature and solvent
polarity range. This way dendronized polymers with their congested structures could
contribute to the important field of helical polymers, which has been explored over the
years, for example, by Okamoto [36], Percec [37], Nolte [38], and Yashima [39]. In
order to achieve such a goal chiral and very compact dendrons had to be developed and
incorporated into dendronized polymers such that their “cross-talking” results in
stable either right- or left-handed helices. 4-Aminoproline moieties were selected as
the branching units and highly efficient synthetic ways developed how to construct
first- and second-generation macromonomers from them as diastereomerically
pure isomers [40]. Ball-and-stick model considerations suggested that certain
