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ELECTRICAL TRANSPORT PROPERTIES OF THE SODIUM HYALURONATE SEMIDILUTE SOLUTIONS

We study electric and dielectric properties of semidilute sodium hyaluronate pure water (no added salt) solutions (Na-HA) by using Dielectric Spectroscopy (DS) technique. For DC electrical conductivity data we take DS data measured at 100 kHz under the applied AC amplitude of 50 mV corresponding to the electric field . We assume that the conductivity has two contributions. The first one is associated with the positively charged sodium counterions. This contribution can be approximated by the molar conductivity of Na+ ions in pure solution . The second contribution is associated with negatively charged hyaluronate polyions. Our results show that the molar conductivity of polyion is and that it slightly decreases with the polyion concentration (c). Standard theories predict that the molar conductivity of polyion is given by , where is the correlation length and f is the proportion of free counterions. In the case of Na-HA which is a weakly charged polyelectrolyte f should be equal to one, i.e. all counterions are free. Our dielectric relaxation data show that the correlation length behaves like , and we get . This means that the concentration dependence of the polyion conductivity is only due to the concentration dependence of the effective proportion of free counterions. The observed decrease of is interpreted to be due to a decrease of effective charge density caused by screening.

dielectric spectriscopy; dynamics of polyelectrolytes; HYALURONATE SEMIDILUTE SOLUTIONS; electrical conductivity; screening

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