Several kinds of commercially available polymers of the type poly(oxy-1,4-p
henylenecarbonyl-1,4-phenylene) were sulfonated by reaction with mixtures o
f sulfuric acid and oleum. The ether/carbonyl group ratio of the polymer ch
ain varied from 0.67 to 2.0. With decreasing amounts of ether links in the
polymer backbone the sulfonation is hindered and the reaction conditions ha
ve to be stronger. To yield the same degree of sulfonation, the sulfuric tr
ioxide concentration of the reaction mixture has to be increased. The achie
vable degree of substitution is limited, in general, to one sulfonate group
per substitutable unit (oxyphenylene-oxy- or oxy-phenylene-carbonyl unit).
In dependence on the polymer structure, polymers with contents of sulfonate
groups between 1.2 and 2.0 meq.g(-1) polymer are well soluble in dimethylf
ormamide or N-methylpyrrolidone and it is possible to produce membranes wit
h permselectivities >96% and electrical resistances <2 Omega cm(-2) .
The sulfonated polymers were characterized by viscosimetry, sedimentation a
nalysis and C-13 NMR spectroscopy.