What is Sodium polystyrene sulfonate?

Polystyrene sulfonates are polymers derived from polystyrene but containing sulfonic acid or sulfonate functional groups. The linear polymer is white when very pure and is water-soluble. The crosslinked material (called a resin) does not dissolve in water and typically appears amber in color. These polymers are classified as polysalts and ionomers. They are widely used to remove ions from a solution in technical or medical applications.