膠體化學(xué)(第13章)課件

1、Chapter 13. Electrostatic and polymer-induced colloid stability13.1 Introduction1. Colloid stability Colloid stability（膠體的穩(wěn)定性）:The stability of a dispersion to resist coagulation.Kinetic stability(動(dòng)力穩(wěn)定性): Evaluated（評(píng)價(jià)） by kinetics.Thermodynamic stability(熱力學(xué)穩(wěn)定性):Evaluated by thermodynamics.Van der W

2、aals 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(電穩(wěn)定作用)。Polymer repulsive force:The adsorbed polymer layer on dispersed particles

3、 masks(屏蔽、對(duì)抗) the attraction force of van der Waals force.Polymer-induced stability(聚合物穩(wěn)定作用) or steric stability(空間穩(wěn)定作用).2. Focus of this chapterThe stability and the structure of dispersions; Structure: spatial(空間的) organization（構(gòu)造、架構(gòu)） of the colloidal particles.How interparticle forces influence t

4、he 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 relation between interparticle forces, the microstructure of di

5、spersions and the factors that determine such a relation.Interpaly between interpartcle forces and structureDominated by strong repulsion;Dominated by strong attraction;Intermediate situations.Interparticle forces and the corresponding microstructure of monodisperse colloidsHow interparticle forces

6、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 measure of kinetiv stability of dispersions.Such a study of sta

7、bility is known as the DLVO theory (Derjaguin-Landau-Verwey-Overbeek, 1940). TR+A （131） T Total interaction energy R Repulsion energy, A -Attraction energy .Boltzman constant， 1/kthickness of electrical double layer0a constant（132）（133）A- Hamaker constantD- Distance between two particles.Effect of t

8、he Hamaker constant AThe height of the potential energy barrier . .2. Effect of the surface potential（0）0 The height of the potential energy barrier . .3. Effect of Electrolyte concentrationk-empirical adjustment (經(jīng)驗(yàn)調(diào)整參數(shù))k is quantity depends on both concentration and valence of the indifference（不相干

9、） electrolyte.kThe height of the potential energy barrier . .15.3 Polymer-colloid mixturePolymers(聚合物) can be used to stabilize colloid and the role of polymers on colloid stability is considerably more complicated than electrostatic stability.If the added polymers are polyelectrolyte(聚電解質(zhì)), then a

10、clearly have a combination of electrostatic effect as well as effects that arise solely(單獨(dú)地) from the polymeric nature of the additive.This combined effect is referred to as electrosteric stabilization（電空間穩(wěn)定）. .A simplified representation of the effects of polymers on the stability of dispersionsBri

11、dging flocculation（橋聯(lián)絮凝）Steric stabilization（空間穩(wěn)定）Depletion flocculation（過渡態(tài)絮凝）Depletion stabilization（過渡態(tài)穩(wěn)定）.The structure of polymer chains in bulk solution and near a solid interface接枝Segment(鏈段).Interaction between polymer-coated particles.Overlap(重疊) of adsorbed polymer layers on close approach

12、 of dispersed solid particles.The various contributions to the interaction energies between two polymer-coated particles.The change in Gibbs energy due to the 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 electrost