Chemistry Reference
In-Depth Information
O
O
Δ
-CO
N
N
O
O
O
O
O
O
N
N
O
N
O
O
N
n
O
O
Only low molecular weight polymers form, however, together with some insoluble, possibly cross-
linked material. Bis maleimides also condense with bisfulvene [
202
]. The products of these
condensations depolymerize reversibly. Also, reactions of maleic anhydride with dienes, like
bicycloheptene, bicyclohexene, dicyclopentenyl ether, and dicyclohexenyl ether, yield soluble, low
molecular weight polymers [
204
]:
O
O
O
O
O
O
O
O
O
+
2
n
Photo-cycloaddition reactions also form low molecular weight polymers with heterocyclic rings in
the backbone. The reactions are photoinitiated with benzophenone to obtain repeated 2
p
+2
p
photo-
cycloadditions of bismaleimides [
205
]:
R'
R'
O
O
path A
R'
R'
R'
R'
O
O
+
hν
N
R
N
R'
R'
N
N
O
O
O
R
path B
O
O
O
O
R' R'
R'
R'
path C
insoluble
crosslinked
polymer
R'
R'
N
R
N
N
R
N
R' R'
O
O
O
O
n
where, R
(CH
2
)
x
.
These polymeric materials form transparent, flexible films [
205
].
¼
