1、Chapter 13. Electrostatic and polymer-induced colloid stability13.1 Introduction1. Colloid stability Colloid stability（胶体的稳定性胶体的稳定性）:The stability of a dispersion to resist coagulation.Kinetic stability(动力稳定性动力稳定性): Evaluated（评价）（评价） by kinetics.Thermodynamic stability(热力学稳定性热力学稳定性):Evaluated by the
2、rmodynamics.Van der Waals force: attractive and is strong at short interparticle separation.There are two forces to against van der Waals force to protect colloid stability: Electrostatic forceelectrical double layer. electrostatic stability(电稳定作用电稳定作用)。 Polymer repulsive force:The adsorbed polymer
3、layer on dispersed particles masks(屏蔽、对抗屏蔽、对抗) the attraction force of van der Waals force.Polymer-induced stability(聚合物稳定作用聚合物稳定作用) or steric stability(空间稳定作用空间稳定作用).2. Focus of this chapter The stability and the structure of dispersions; Structure: spatial(空间的空间的) organization（构造、（构造、架构）架构） of the
4、 colloidal particles. How interparticle forces influence the structure of a dispersion; How the influence of interparticle interaction energies on dispersion stability; How polymer influence the stability of dispersions.13.2 Interparticle forces, structure and stability of dispersionsTo know the rel
5、ation between interparticle forces, the microstructure of dispersions and the factors that determine such a relation.Interpaly between interpartcle forces and structureDominated by strong repulsion;Dominated by strong attraction;1. Intermediate situations.Interparticle forces and the corresponding m
6、icrostructure of monodisperse colloidsHow interparticle forces and the concentration of the particles to determine the structure of dispersions.13.3 Interaction energy curves and their dependence on the properties of the dispersionThe Interaction energy curves are useful for developing quantitative
7、measure of kinetiv stability of dispersions.Such a study of stability is known as the DLVO theory (Derjaguin-Landau-Verwey-Overbeek, 1940). TR+A （131） T Total interaction energy R Repulsion energy, A -Attraction energy .212 DAA20064kDRnTekBoltzman constant， 1/kthickness of electrical double layer0a
8、constant（132）（133）A- Hamaker constantD- Distance between two particles. Effect of the Hamaker constant AThe height of the potential energy barrier . .2. Effect of the surface potential（0 0）0 The height of the potential energy barrier . .3. Effect of Electrolyte concentrationk-empirical adjustment (经
9、验调整参数经验调整参数)k is quantity depends on both concentration and valence of the indifference（不相干）（不相干） electrolyte.kThe height of the potential energy barrier . .15.3 Polymer-colloid mixturePolymers(聚合物聚合物) can be used to stabilize colloid and the role of polymers on colloid stability is considerably mor
10、e complicated than electrostatic stability.If the added polymers are polyelectrolyte(聚电聚电解质解质), then a clearly have a combination of electrostatic effect as well as effects that arise solely(单独地单独地) from the polymeric nature of the additive.This combined effect is referred to as electrosteric stabil
11、ization（电空间稳定电空间稳定）. .A simplified representation of the effects of polymers on the stability of dispersionsBridging flocculation（桥联絮凝）（桥联絮凝）Steric stabilization（空间稳定）（空间稳定）Depletion flocculation（过渡态絮凝）（过渡态絮凝）Depletion stabilization（过渡态稳定）（过渡态稳定）.The structure of polymer chains in bulk solution and
12、near a solid interface接枝接枝Segment(链段链段).Interaction between polymer-coated particles.Overlap(重叠重叠) of adsorbed polymer layers on close approach of dispersed solid particles.The various contributions to the interaction energies between two polymer-coated particles.The change in Gibbs energy due to th
13、e overlap of the tails, loops, and so on.Interaction forces between polymer-coated surface and their dependence on the type of layers and quality of the solvent.Combination of the electrostatic effects and steric stabilization. TRAS SEnergy potential of steric stabilization .Effects of particles on the interface between oil drops and water is like the steric effect of polymers.
