
194 HIGH PERFORMANCE POLYMERS
of 3,3
-disulfonated 4,4
-difluorodiphenyl sulfone and
4,4
-difluorodiphenyl sulfone with 4,4
-biphenol and
1,3-bis-(4-hydroxyphenyl) propenone [120]. The con-
tent of crosslinkable moieties in the polymer repeat
unit can be controlled by changing the monomer feed
ratio. The polymer membranes can be crosslinked by
irradiating with UV.
The crosslinked membranes show less water uptake,
a lower level of methanol permeability, and good ther-
mal and mechanical properties in comparison to pris-
tine membranes while maintaining a reasonable level
of proton conductivity [120].
7.4.1.8 Direct Methanol Fuel Cells
Sulfonated PPESK membrane ...