Chemistry Reference
In-Depth Information
O
R
+
S
SO
2
n
O
R
Aliphatic sulfones, however, lack good thermal stability and are not commercially important.
Aromatic sulfones, on the other hand, have many desirable physical properties. They are clear, rigid,
tough materials, with a high
T
g
. Several aromatic sulfones are prepared commercially.
The original preparation of aromatic polysulfones was described in 1958 [
110
]. This was followed by
investigations of many different structures of polysulfones. One current commercial material is a
condensation product of 2,2
0
bis(hydroxyphenyl) propane with 4,4
0
-bis(chlorophenyl) sulfone. It forms
by aWilliamson synthesis, because the reactivity of the halogens is enhanced by the sulfone groups [
47
]:
O
S
n
+
n
O
NaO
ONa
Cl
Cl
O
S
+
O
2n NaCl
O
O
n
The condensation takes place at 160
C in an inert atmosphere and in some suitable solvents, like
chlorobenzene. Commercially, polymers are available in molecular weight ranges from 20,000 to
40,000. Much higher molecular weight materials, however, form readily.
Aromatic polysulfones also form by the Friedel-Craft reaction [
111
], as for instance:
O
O
Lewis
acid
n
O
+
O
n HCl
Cl
S
S
n
O
O
or
O
O
Lewis
acid
n
+
Cl
S
O
S
n
Cl
O
O
O
O
S
O
S
n
O
O
The reaction takes place at 80-250
C in a solution or in the melt. Lewis acid catalysts are used in
concentrations of 0.1-1.0 mole percent. Cross-linking through polysubstitution does not appear to be
a problem. Some chain branching, however, does occur because
ortho
substitution is possible:
