Experimental Verification of "Electrodynamic" Interaction

我们提出了“电动相互作用”作为胶体晶体形成的驱动力。为了阐明离子聚合物颗粒间这种新型作用力的机理，我们利用超小角X射线散射（USAXS）进行了系统的实验研究。胶体晶体中的颗粒间距离被认为是随着离子强度的增加而减小。然而，我们发现当添加的盐浓度低于10 μ M时，它增加<-5>。这一事实意味着胶体粒子之间的有效相互作用应该是一种吸引作用，但这种吸引作用的机理应该与已有的理论不同。我们认为粒子周围的反离子对胶体晶体的形成起着重要的作用。作为第一个实验，我们将反离子物种从质子改变为钠离子。随着质子向钠离子的交换，颗粒间距发生变化。这一事实当然意味着颗粒间的相互作用受到共存种的影响。其次，我们使用钾、锂和四甲基铵（TMA）离子作为抗衡离子。由USAXS评估的粒子间距离再次取决于抗衡离子种类。这些离子使相互吸引作用弱于质子，并且这种作用按钾&gt;钠&gt;TMA=锂的顺序增强。这种顺序与这些阳离子的表面电荷密度，即反离子的扩散常数，是一致的。因此，我们可以得出以下结论：（1）当离子强度低于10 μ M时，“电动相互作用”是有效<-5>的。(2)在这种情况下，反大气层高度重叠。(3)大气中的反离子可以在胶体晶体中的任何位置移动。(4)相互作用力取决于对流扩散的速度。(5)强吸引相互作用仅在对电子是质子时才能观察到。因此，吸引力的来源应该是质子的高电导率。

We have proposed "Electrodynamic Interaction" as a driving force of colloidal crystal formation. To clarify the mechanism of this novel force between ionic polymer particles, we have performed the systematic experiment by ultra-small-angle X-ray scattering (USAXS). The interparticle distance in the colloidal crystal was believed to decrease with increasing ionic strength. However, we found that it increased when added salt concentration is below 10^<-5>M. This fact means the effective interaction between colloidal particles should be an attractive one, which should based on difference mechanism from the theory already proposed, however. We thought that the counterions around particles have an important role for colloidal crystal formation. As the first experiment, we changed counterion species from proton to sodium ion. With exchanging from proton to sodium ion, the interpaticle distance changed. This fact certainly means that the interpaticle interaction is affected by counterion species. Secondaly, we used potassium, lithium, and tetramethylammonium (TMA) ions as counterions. The interparticle distance evaluated by USAXS again depended on the counterions species. These ions made the attractive interaction weaker than proton, and this effect is stronger in the order of potassium>sodium>TMA=lithium. This order is in good agreement in that for surface charge density of these cations, i.e. diffusion constant of counterions. Hence, we can conclude as following;(1) "Electrodynamic Interaction" is effective when ionic strength is below 10^<-5>M.(2) At this condition, the counterion atmosphere is highly overlapped.(3) The counterions in atmosphere can move anywhere in the colloidal crystal.(4) The interaction force depends on speed of counterion diffusion.(5) The strong attractive interaction is observed only when counterion is proton. Hence, the origin of attraction should be anomalously high electric conductivity of protons.