Thermodynamic, transport and frictional properties in semidilute aqueous sodium carboxymethylcellulose solution

• Counterion-condensation in sodium carboxymethylcellulose solution (aq) was studied.
• Scaling theory approach for the polyion configuration was used to analyze the data.
• Counterion-condensation in the polyelectrolyte solutions was found to be spontaneous.
• Degree of substitution of the sample greatly influences the counterion-condensation.
• Polyion size effect overrides the charge effect in governing the polyion mobility.

Electrical conductivities of aqueous solutions of an anionic polyelectrolyte sodium carboxymethylcellulose with different degrees of substitution have been reported as a function of concentration and temperature. The conductance-concentration data have been analyzed with the modified Manning counterion-condensation model appropriate for semidilute polyelectrolyte solutions, considering the de Gennes scaling description of the polyion configuration. 36–55% of the counterions were found to remain condensed and the condensation process was shown to be spontaneous. Although the level of counterion-condensation depends appreciably on the degree of substitution, it was found to remain invariant with the polyelectrolyte concentration and the temperature. The free energies of counterion-condensation, the ratios of the mobility of the polyion to that of the counterion, the polyion transference numbers, and the coefficients of monomer-solvent friction have been evaluated. The effects of the polyion charge, its size, and the bulk viscosity of the media on the polyion-counterion interactions have also been discussed.

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