Chemistry Reference
In-Depth Information
7.17.7 Cardo Polymers
These are a special group [
201
,
208
,
220
] of polymeric materials. The name cardo comes from Latin,
meaning loop [
201
,
208
]. The polymers contain cyclic structures that may be perpendicular to the
aromatic backbones. An example would be a cardo polybenzimidazole:
N
N
N
n
N
H
H
Another example is a cardo polyester [
201
,
208
]:
O
O
n
O
O
Many cardo polymers exhibit improved solubility in different solvents with little sacrifice in
properties. A survey was made of the physical properties of different cardo copolyimides with
varying microstructures [
220
]. As might be expected, copolyimides with increasing aliphatic frag-
ment content were shown to exhibit the highest impact and flexural strength.
7.17.8 Double-Stranded Polymers
Preparations of many double-stranded polymers were reported. For instance, polypyrrolones were
formed from 2,3,5,6-tetraaminobenzene and various dianhydrides or tetracarboxylic acid compounds
[
213
]. Following are two examples:
O
O
H
2
N
H
2
N
NH
2
NH
2
+
O
O
1.
O
O
O
O
N
N
n
N
N
