Kamburova Kamelia, Radeva Tsetska
Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria.
J Colloid Interface Sci. 2007 Sep 15;313(2):398-404. doi: 10.1016/j.jcis.2007.05.026. Epub 2007 May 16.
Electrical properties of sodium carboxymethyl cellulose (NaCMC) in aqueous solution and after addition to a dilute suspension of beta-ferric hydrous oxide particles (beta-FeOOH) are studied by means of electric birefringence method. We established extended conformation of the NaCMC chains in a solution at concentration 10(-2) g dm(-3), which is found high enough to assure overcharging of the particle surface. The frequency behavior of the electric birefringence of NaCMC solution with concentration 10(-2) gdm(-3) is found similar to the behavior of the suspension of beta-FeOOH particles containing same amount of polyelectrolyte. The observed decrease in the relaxation frequency of the electro-optical effect in both systems is attributed to polarization of condensed counterions near to the polyion surface. These results are in line with our previous estimation, showing that the condensed counterions are not released from NaCMC because of its adsorption onto weakly charged particle surface. They also reveal that, at overcompensation of the particle charge, the electrical properties of the adsorbed polyion dominate the electro-optical behavior of the weakly charged particle.
采用电双折射法研究了羧甲基纤维素钠（NaCMC）在水溶液中以及添加到β-氢氧化铁水合物颗粒（β-FeOOH）稀悬浮液后的电学性质。我们确定了浓度为10⁻² g dm⁻³的溶液中NaCMC链的伸展构象，发现该浓度足以确保颗粒表面的过充电。发现浓度为10⁻² gdm⁻³的NaCMC溶液的电双折射频率行为与含有相同量聚电解质的β-FeOOH颗粒悬浮液的行为相似。在两个系统中观察到的电光效应弛豫频率的降低归因于聚离子表面附近凝聚抗衡离子的极化。这些结果与我们之前的估计一致，表明凝聚抗衡离子不会因吸附在弱带电颗粒表面而从NaCMC中释放出来。它们还表明，在颗粒电荷过补偿时，吸附的聚离子的电学性质主导了弱带电颗粒的电光行为。
