Synthesis of N‐hydroxymethyl acrylamide with β‐methyl hydrogen itaconate and itaconic acid hydrogels: Effects of the pH, composition, and ionic strength on the swelling behavior

Copolymer gels were prepared by the radical copolymerization of N‐hydroxymethyl acrylamide with itaconic acid and N‐hydroxymethyl acrylamide with β‐methyl hydrogen itaconate. The ratios of both monomers were varied from 25 to 75 mol %, and the effects of external stimuli such as the pH and ionic strength of the swelling media were investigated. The gels were pH‐responsive, and an increase in the ionic strength of the solutions caused a decrease in the equilibrium degree of swelling of the copolymer gels. The monomer reactivity ratios were determined with the Kelen–Tüdös method. Moreover, the copolymer composition had a significant effect on the equilibrium swelling behavior of the two copolymers investigated.