Liu Bo-Tau, Hsu Jyh-Ping
Department of Chemical and Materials Engineering, National Yunlin University of Science and Technology, Yunlin, Taiwan 64002.
Langmuir. 2009 Aug 18;25(16):9045-50. doi: 10.1021/la900810g.
The stability of a salt-free dispersion containing soft spherical colloidal particles is investigated theoretically. Here, a particle comprises a rigid core and an ion-penetrable membrane layer; the ionic species in the liquid phase come solely from those dissociated from the functional groups in the membrane layer. We show that, similar to the case of a salt-free rigid dispersion, the total energy, which comprises the electrical energy and the van der Waals energy, is always positive far away from the surface of a particle and does not have a secondary minimum. Both the Derjaguin approximation for the estimation the electrical energy of two spheres and the criteria for the critical coagulation concentration in the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory are inapplicable. If the molar concentration of the fixed charge in the membrane layer exceeds ca. 0.1 M, the stability of a dispersion remains roughly the same. The maximum allowable particle concentration for a stable dispersion for the case of soft particles is lower than that for the case of the corresponding rigid particles.
对含有软球形胶体颗粒的无盐分散体系的稳定性进行了理论研究。在此，颗粒由刚性核和离子可渗透的膜层组成；液相中的离子种类仅来自于膜层中官能团解离出的离子。我们表明，与无盐刚性分散体系的情况类似，由电能和范德华能组成的总能量在远离颗粒表面处总是正的，并且没有第二极小值。用于估计两个球体电能的德亚金近似以及德亚金 - 朗道 - 韦弗 - 奥弗贝克（DLVO）理论中的临界聚沉浓度准则均不适用。如果膜层中固定电荷的摩尔浓度超过约0.1 M，分散体系的稳定性大致保持不变。软颗粒情况下稳定分散体系的最大允许颗粒浓度低于相应刚性颗粒情况下的最大允许颗粒浓度。
