Chemistry Reference
In-Depth Information
Diels-Alder reaction can also be used to modify the chemical structures of some aromatic
polyamides. This improves their heat stability, raises their
T
g
value, and makes them rigid at higher
temperatures [
203
].
7.17.4 Silicon-Containing Aromatic Polymers
These materials have the potential of being stable at high temperatures. One typical preparatory
procedure consists of condensing bisphenols with suitable silicon derivatives [
227
]:
R
R
2
Si(OR)
2
or
R
2
SiCl
2
+
HO
Ar
OH
Si
O
Ar
O
R
n
Many of these polymers are soluble and exhibit good heat stability. An example is one such
material prepared by this procedure and shown below:
Si
O
O
n
It looses only 10% of its weight at 600
C[
191
].
The starting materials can also be silanols, as for instance in a synthesis of polycarbonates [
227
].
Preformed bis-silanols are used in this particular example:
O
O
Si
Si
Si
Si
n
+
Cl
HO
O
N
n
O
OH
x
x
OO
Cl
O
Si
Si
Si
Si
O
O
x
x
OO
n
where,
0or1.
One publication describes syntheses of copolyesters and copolyamides that contain phenoxalin
rings [
228
]:
x ΒΌ
