Polyion–counterion interactions in sodium carboxymethylcellulose–ethylene glycol–water ternary solutions

► Sodium carboxymethylcellulose was studied in aqueous glycol (EG) conductometrically. ► Concentration-dependent moderate counterion condensation (24–33%) was observed. ► Counterion condensation is spontaneous and depends upon EG-content and temperature. ► A major part of the current is transported by the carboxymethylcellulose polyions. ► Monomers feel more friction as EG-content increases and temperature decreases. Polyion–counterion interactions in sodium carboxymethylcellulose–ethylene glycol–water ternary system have been investigated with special reference to their variations with the polyelectrolyte concentration, the medium relative permittivity and the temperature using electrical conductance measurements. The experimental data have been analyzed on the basis of a model for semidilute polyelectrolyte conductivity which takes into account the scaling arguments proposed by Dobrynin et al. Concentration-dependent moderate counterion condensation (24–33%) was observed. Counterion condensation is found to be spontaneous which depends upon the EG-content of the medium and the temperature. A major proportion of the current is transported by the carboxymethylcellulose polyions. The results further demonstrated that the monomer units experience more frictional resistance in solution as the EG-content increases or as the temperature decreases.