Transport of Ions inside Polymer Gel in an Electric Field

Abstract

The transport of ions inside polymer gel in an electric field was investigated experimentally and theoretically using two kinds of nonionic gels of different bridge formation, containing electrolyte (salt) solution (Na₂SO₄ or KNO₃). The change of pH, concentration of salt and electric potential distribution inside the gel were measured. A mathematical model of diffusion and migration of ions was developed to predict the behavior of ions inside the gels in an electric field. Experimental results were well predicted by this model. The diffusion coefficients of ions inside the gels were also determined by fitting the results of calculation with experimental data, and the values were smaller than those in solution. It is considered that the decrease in diffusion coefficients in the gels depends on the tortuosity of diffusion path based on the tridimensional network structure of the gels. The tortuosities of polyacrylamide (PAcAm) and polyvinyl alcohol (PVA) gels were calculated as 2.8–3.1 and 2.5–2.6 respectively.