Key points are not available for this paper at this time.
Polysulfone has been sulfonated to varying degrees using a sulfur trioxide–triethyl phosphate complex as the sulfonating agent. These conditions are suitable for surface sulfonation as well as solution sulfonation. The neutralized, sodium salt form is much more stable than the free acid form. The glass transition temperature of polysulfone is increased by as much as 130°C (i.e., to 310°C) by the introduction of SO3Na groups. Sulfonation also causes a major shift in the low-temperature (−100°C) transition of polysulfone. Compositions of intermediate degree of sulfonation, containing 0.5 SO3Na groups per polysulfone repeat unit, are melt processable. This composition also displays the best balance of properties. Water absorption, which exerts a large influence on mechanical properties, ranges from 1% to 61%, depending upon degree of sulfonation and sorption conditions. Water absorption and desorption curves show non-Fickian behavior. Compositions of intermediate degree of sulfonation display optimum reverse osmosis desalination behavior. Gas permeability is significantly reduced by sulfonation. Overall behavior is consistent with an ionomer-type structure.
Noshay et al. (Thu,) studied this question.