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molecular weights of up to 300 kDa can be synthe-
sized. Such high-molecular-weight polyelectrolytes
are proposed for their use in fuel cells.
5.2.5 Modification of PPS by Nitro
Groups
PPS as such can be modified with nitro groups as
common by a mixture of nitric acid and sulfuric acid.
The nitro groups can be further reduced by the appli-
cation of sodium dithionite [35].
The thermal stability is progressively reduced by
the introduction of these functional groups. In partic-
ular, the aminated derivatives are less thermally stable
and have a higher solubility in aprotic polar solvents
than the nitrated polymers. With an increasing degree
of functionalization the crystallization temperature
lowers and the glass transition temperature ...