Dynamic and equilibrium swelling of a sulfonic acid superabsorbent copolymer in salt solutions

Superabsorbent copolymers were synthesized by free radical reverse emulsion from the monomers acrylamide and 2‐acrylamido‐2‐methyl‐propanosulfonic acid with a divinyl crosslinker (methylene‐bisacrylamide). The copolymer synthesized was then identified by Fourier transform infrared spectroscopy, its porosity was examined by electronic microscopy, and its specific gravity was determined by the conventional procedure. The dynamic and equilibrium swelling behavior of the copolymer was studied, in water and in salt solutions, at 25 °C (chlorides and sulfates of sodium and magnesium). As to the equilibrium swelling, the influence of the pH as well as of the salt type and its concentration was observed. As to the dynamic swelling, it was interpreted in terms of both a simple power of time equation, and a more detailed model based on a coupled diffusion‐relaxation mechanism.