Institute of Physical Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 11, Sofia 1113, Bulgaria.
J Phys Condens Matter. 2010 Dec 15;22(49):494112. doi: 10.1088/0953-8984/22/49/494112.
Polyelectrolytes are soluble polymers composed of units having charged groups. Because of the high charge density, some of the counterions are adsorbed electrostatically (ion condensation) on the polyelectrolyte chain. It was shown that in direct electric field the condensed counterions and the chain move together as one whole but it is assumed that they are mobile in alternating field and participate in the polarization. Experimental evidence is obtained by electro-optical investigations of polyelectrolytes adsorbed on colloid particles-the observed low-frequency shift of the polarizability relaxation has been interpreted as condensed counterions' mobility. The present investigation aims to verify the reports for the condensed counterions' mobility in sinusoidal electric field. By means of electric light scattering we investigated a water suspension of γ-alumina particles with adsorbed carboxymethyl cellulose. Instead of the previously used frequency approach (dispersion dependence at saturated adsorption of the polyelectrolyte) we applied an amplitude approach-determination of the polarizability at frequency 1 kHz and increasing polyelectrolyte concentration (from zero to full adsorption saturation). The results indicate the absence of polarization owing to the condensed counterions. The main evidence was obtained by comparison of the concentration dependences of the polarizability (depending on all mobile counterions) and the electrophoretic mobility (determined only by the diffuse counterions). We concluded that the condensed counterions are immobile in sinusoidal field with intensity up to 0.5 kV cm (- 1) and frequency of 1 kHz and higher.
聚电解质是由带有电荷基团的单元组成的可溶性聚合物。由于高电荷密度，一些抗衡离子被静电吸附（离子凝聚）在聚电解质链上。已经表明，在直流电场中，凝聚的抗衡离子和链作为一个整体一起移动，但假设它们在交变电场中是可移动的，并参与极化。通过对吸附在胶体颗粒上的聚电解质的电光研究获得了实验证据-观察到的极化率弛豫的低频移动被解释为凝聚抗衡离子的流动性。本研究旨在验证在正弦电场中凝聚抗衡离子流动性的报告。我们通过电光散射研究了带有吸附羧甲基纤维素的γ-氧化铝颗粒的水悬浮液。我们应用了一种幅度方法，而不是以前使用的频率方法（聚电解质饱和吸附时的色散依赖性）-在频率 1 kHz 时确定极化率，并增加聚电解质浓度（从零到完全吸附饱和）。结果表明，由于凝聚的抗衡离子，不存在极化。主要证据是通过比较极化率的浓度依赖性（取决于所有可移动的抗衡离子）和电泳迁移率（仅由扩散抗衡离子决定）获得的。我们得出结论，在强度高达 0.5 kV cm（-1）和频率为 1 kHz 及更高的正弦场中，凝聚的抗衡离子是不可移动的。
