Low-frequency dynamics of counterion polarization in aqueous polyelectrolyte as studied by electric birefringence relaxation methods

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Abstract
The low-frequency relaxation of aqueous polyelectrolytes was studied by both the time-domain electric birefringence (TEB) and the frequency-domain electric birefringence (FEB) methods. Both the methods allow us to determine the rotational relaxation time τr of the polyion as well as the dielectric relaxation time τ given as a harmonic mean of τr and the intrinsic relaxation time τr of counterion polarization. The values of the relaxation times obtained by these two methods agree very well with each other, where τr is found to be smaller than τr by an order of magnitude. The observed value of τr suggests that the translational diffusion constant of counterions along the polyion should be much smaller than that in the free medium.