INFLUENCE OF A SALT ON THE PROPERTIES OF HYDROGELS OF 2-HYDROXYETHYL METHACRYLATE WITH A SULFOBETAINE COMONOMER

Copolymeric hydrogels of 2-hydroxyethyl methacrylate (HEMA) and N,N-dimethyl-N-[(methacryloyloxy)ethyl]-N-(3-sulfopropyl)ammonium betaine (SPE) have been prepared by means of gamma-irradiation. The variation of the swelling and mechanical properties of these gels with the concentration of potassium thiocyanate in the swelling medium has been examined. The results have been analyzed and quantified via the application of the Donnan-type equilibrium theory in conjunction with the equilibrium thermodynamics of ternary systems solvent/polymer/solvent. In this manner, relevant water/polymer, salt/water, and salt/polymer interaction parameters have been obtained. The thermodynamic analysis shows the importance of the nearest-neighbor interactions in SPE-based systems and indicates that copolymers prepared from SPE and HEMA represent an appropriate model system to study the above-mentioned interactions.