Institute of Physical Chemistry, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria.
Langmuir. 2010 Sep 21;26(18):14488-93. doi: 10.1021/la102428k.
The investigation presents results on the low-frequency electrical polarization of β-FeOOH particles with adsorbed layers from sodium salts of poly(4-styrene sulfonate), poly(acrylic acid), and carboxymethyl cellulose, obtained by electric light scattering. The adsorption is realized in aqueous NaCl solutions of different concentration, and the suspensions of the coated particles are then rinsed to low conductivity. Several electro-optical parameters are sensitive to the conformation of the adsorbed polyelectrolyte layer. The particle electrical polarizability increases drastically with the concentration of NaCl (correlating with significant increase of the adsorbed amount of polyelectrolyte), while their electrophoretic mobility remains practically unchanged. Two time scales are involved in the stepwise relaxation of the electrical polarizability. The faster process is attributed to movement of ions in the polymer layer, restricted by the coiled conformation to smaller distances. The contribution of the Debye atmosphere outside the polymer layer remains almost unchanged, which correlates with the low sensitivity of the electrophoretic mobility to the increasing amount of adsorbed polyelectrolyte. Abrupt increase in a narrow interval of salt concentrations is observed both for the low-frequency component of the particle polarization and for the hydrodynamic layer thickness, indicating changes in the surface electric state, most probably due to swelling of the adsorbed polymer layer.
研究结果表明，通过电光散射法可以得到吸附有聚（4-苯乙烯磺酸钠）、聚丙烯酸和羧甲基纤维素的β-FeOOH 颗粒的低频电极化。吸附是在不同浓度的 NaCl 水溶液中实现的，然后将涂覆的颗粒悬浮液冲洗至低电导率。几个电光参数对吸附聚电解质层的构象敏感。颗粒的电极化率随 NaCl 浓度的增加而急剧增加（与聚电解质吸附量的显著增加相关），而其电泳迁移率基本保持不变。电极化率的逐步弛豫涉及两个时间尺度。较快的过程归因于聚合物层中离子的运动，由于螺旋构象的限制，离子只能在较小的距离内运动。聚合物层外的 Debye 气氛的贡献几乎保持不变，这与电泳迁移率对吸附聚电解质量的增加的低敏感性相关。在盐浓度的狭窄间隔内观察到颗粒极化的低频分量和流体动力学层厚度的突然增加，表明表面电荷状态发生变化，很可能是由于吸附聚合物层的溶胀。
