Chemistry Reference
In-Depth Information
This double-stranded polymer, shown above, is soluble only in hexafluoroisopropyl alcohol [
198
]
and is infusible. When, however, some of the rings are made flexible by condensing 2-vinyl-1,3-
butadiene with a large ring bis fumarate, the solubility improves [
198
].
Some stable polymers also form in 1,3-dipole addition reactions [
190
]. Bis-sydnones, for instance,
condense with diacetylene to form pyrazole rings in the polymer backbone. The reactions presumably
proceed through Diels-Alder intermediates [
199
]:
H
O
N
O
+
N
N
NC
CN
O
N
O
H
N
N
N
N
n
Similarly, bis-sydnones condense with quinone [
199
]:
O
O
H
O
+
N
N
O
N
N
N
N
O
N
N
O
n
H
O
O
The resultant polymers are not high in molecular weights and only slightly soluble in solvents like
dimethylformamide. Their powders decompose near 420
C in air and near 500
C in a nitrogen
atmosphere.
1,3-Dipolar additions of bisnitrileimines (generated from tetrazoles with dienes or with di nitriles)
result in formations of polypyrazoles and polytriazoles [
200
]. Some examples of these reactions are:
N
N
N
N
N
N
+
N
N
NC
CN
N
N
N
N
N
N
n
