胶体化学专业英语.ppt

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1、Colloid Chemistry（胶体化学专业英语）,ContentChapter 1.Colloid and Interface ChemistryChapter 2.Sedimentation and diffusion and their equilibriumChapter 3.Osmotic Pressure and Donnan EquilibriumChapter 4.The Rheology of DispersionsChapter 6.Surface Tension and Contact AngleChapter 7.Adsorption from solution a

2、nd monolayer formationChapter 8.Colloidal structures in surfactant solutionChapter 9.Adsorption at Gas-Solid interfaceChapter 10.wan der Waals ForcesChapter 11.Electrical double layer and Double layer interactionsChapter 12.Electrophoresisand other electrokinetic phenomenaChapter 13.Electrostatic an

3、d polymer-induced colloid stability,Chapter 1.Colloid and Interface Chemistry,1.1 Colloid Chemistry1.Colloid（胶体）?Colloid：A dispersion of the particle that has some linear dimension between 1 and 1000（100）nm.,Definition of dispersion：Dispersion（dispersion system)dispersed phase(分散相)continuous phase(连

4、续相)or dispersion medium(分散介质)Any solid,liquid and gas can be as a dispersed phase or continuous phase.,2.Classification of dispersions(分散体系分类)True solution(分子分散体系):There is not interface between dispersed phase and dispersion medium.Colloid dispersion(colloid solution)(胶体分散体系:Linear dimension of par

5、ticles is between 1 and 1000（100）nm.Coarse dispersion(粗分散体系):Dimension of particles 1000 nm.,3.Classification of colloids(胶体体系分类),Lyophilic colloids（亲液胶体）Colloids Lyophobic colloids（憎液胶体）,Colloids are classified on the basis of the affinity of the surface of the particles to the continuous phase.,Ly

6、ophilic(solvent loving）or hydrophilic(water is the medium or solvent)Lyophobic(solvent fearing）or hydrophobic(water is the medium or solvent),(1)Lyophilic colloids:Macromolecular solution Polymer solution.B.Micelle(胶束、胶团)solution Micelles are clusters（团、束）of small molecules that form spontaneously（自

7、发的）in aqueous solution mostly.Micelle solution is often called association colloids（缔合胶体）.,Type of micelleCylindrical micelleBilayerBilayer vesicleInverted micelleMicrotubule,Why?A.The size of macromolecules and micelles is in the range of 1-1000 nm.B.There is not interface between dispersed phase a

8、nd continuous phase.The solution is stable thermodynamiclly（热力学）.C.Properties of the solutions like colloids.such as optical（光学的）,rheological（流变的）properties.,(2)Lyophobic colloids：There is a interface between dispersed phase and continuous phase,the colloids are unstable thermodynamically.Lyophobic

9、colloids are known by a variety of terms,depending on the nature of the phases involved.,Summary of Some of the Descriptive Names Used to Designate Two-Phase Colloidal（Lyophobic colloids）Systems,After water floodingReservoir is a dispersionsystem of water,crudeand rock are both dispersed and continu

10、e phase.,There is a huge interface of oil/water,oil/rock and water/rock.,4.Stability of colloids,(1)Concept of stability of colloidal systems Lyophilic colloids form true solutions,and true solutions are produced spontaneously when solute and solvent are brought together.In the absence of chemical c

11、hanges or changes of temperature,a solution is stable indefinitely.,Finely subdivided（精细粉碎的）dispersions(lyophobic colloids)of two phases do not form spontaneously when the two phase are brought together.If such a dispersion is allowed to stand long enough,the reverse（相反的）process would spontaneously

12、occur（发生）(separation of phases,unstable).,From thermodynamics that spontaneous process occur in the direction of decreasing Gibbs free energy.Therefore，the separation of a two-phase dispersion system to form distinct（明显不同的）layers（层）is a change in the direction of decreasing Gibbs free energy.,(2)Kin

13、etic stability(动力稳定性),Kinetic stability：The separation rate of two phases is slow enough that the thermodynamic instability is of very little.Two-phase dispersions will always spontaneously change into a smaller number of larger particles given sufficient time.(unstable),Macromolecular solutions do

14、not undergo spontaneous separation into two phases.(stable)We should realized that the words(unstable,stable)are meaningless unless the process to which they are applied has been clearly defined.,Coarsening process of a thermodynamically unstable dispersion,Coalesence(coagulation)(聚并):Two or more sm

15、all particles fuse（融合）together to form a single larger particle.The total surface(interface)area is reduced.,Aggregation（flocculation）（絮凝、聚集）:small particles clump together like a bunch of grapes,but do not fuse into a new particle.no reduction of interface.,Kinetically stable:A colloid that is able

16、 against coalesence or aggregation.The classical use of the term“colloid stability”represents kinetic stability,Ec-energy barrierkBT-thermal energy,(3)Thermodinamic stability(热力学稳定性),In the absence of chemical changes or changes of temperature,no changes of Gibbs free energy for a solution or a coll

17、oid(Lyophilic colloids).e.g.Macromolecular solution,micelle solution,microemulsion.,5.Some physical characterisrestics of colloids,Particle size and shapeParticle size:Small:1-1000 nm;Monodisperse:the size of particles is homogeneous;,Polydisperse:the size of particles is varieous.,Particle shape:Pa

18、rticles with a high degree of symmetry Solid particles are not actually spherical,but have a high degree of symmetry.Particles with a low degree of symmetry solid particles:ellipsoid,disk-like,rod-like,needle-like;flexible materials:line,random coil,branch,network.,Model particles The size,shape and

19、 surface of the particles can be controlled.,(2)Particle aggregates,In many situations the dispersed phase is present as aggregates,in such cases,it is the size,shape,and concentration of the aggregates that determine the properties of the dispersion itself.,(3)Polydispersity and average diameter of

20、 particles,Colloids are polydispersed,average diameter Number average：dn Surface average：ds Volume average：dv Monodispersion：dn=ds=dv Polydispersion：dn ds dv,Polydispersity(多分散度)Ratio of surface average diameter to number average diameter（ds/dn）.（ds/dn）1 The larger the ratio,the wider the distributi

21、on of the diameters of the particles is.,Molecular weight average Used for macromolecular solution.Number-average molecular weight：Mn Weight-average molecular weight:Mw Polydispersity Ratio of Weight-average molecular weight to Number-average molecular weight.Mw/Mn 1 Monodispersion：Mn=Mw Polydispers

22、ion：Mw Mn The larger the ratio,the wider the distribution of the molecular weight is.,6.Characteristics of colloids,High polydispersity（高分散度）(various particle size)Multy-phases（多相）(bulk phases,interface)Thermodynamically unstable(have an interface)Various shapes and structures of dispersed phase(dis

23、k-like,branch,aggregates,network),Size and shape of particles dominate the properties of colloids.,7.Classification and characteristics of dispersions,Colloid Chemistry?,A science to study colloidal dispersion,macromolecular solution and micelle solution.,1.2 Interface chemistry,Surfaces and Interfa

24、cesSurfaces:A face between substances and air(classically).物体与真空、本身的饱和蒸气或含饱和蒸气的空气相接触的面。,2.Interfaces:A face between any substances.Solid/liquid,solid/air,solid/solid,liquid/air,liquid/liquid.,The word Surface or interface is used in the chemical sense of a boundary（边界）rather than a strictly geometri

25、cal（几何的）sense.Gemetrically,a surface has area but not thickness.Chemically,it is a region(interphase)in which the properties vary from those of one phase to those of the adjoining（相邻的）phase.,3.Interface chemistryA science to study properties of the interfaces between substances.,4.Relations between

26、colloids and interfaces,Changes for 1 cm3 water.,Colloids and Interface is like a twins（双胞胎）Colloid chemistry:Focus on particles and properties of whole system(colloids,dispersions).Interface chemistry:Focus on the inter-phase between the two bulk phases（体相）.,Specific surface area（1）volume specific

27、surface area Surface area of unit volume particles.(11)ASvolume specific surface area（m-1）（2）mass specific surface area Surface area of unit mass particles.（12）Asp mass specific surface area（m2/kg，m2/g）,Chapter 2.Sedimentation and diffusion and their equilibrium（平衡）,2.1 Introduction Why?Sedimentatio

28、n（沉降）and diffusion（扩散）affect many colloidal phenomena.Basic principles of sedimentation and diffusion are essential（基本的）part of colloid science.Many analytical（分析的）and preparative（预备、准备）technology take advantage of S&D in colloid science(biophysics,biochemistry).,2.PurposeTo introduce the basic conc

29、epts（概念）that govern（控制）S&D of colloidal particles.Discuss Stokess law Stokess law is a key relationship in understanding the sedimentation rate of colloidal particles.Fickes laws Focus our attention on the diffusion coefficient（常数）.,Equilibrium between sedimentation and diffusion of colloidal partic

30、les.Brownian motion（布朗运动）(random walks)and diffusion,2.2 Sedimentation,1.Basic considerationsFg:gravity force(+),Fb:buoyant forceFv:viscous forcewhen 2 1 Sedimentationwhen 1 2 Creaming,Fv=f v(2),f:friction factor(kg s-1)v:stationary state velocity,(1),Since the net force of gravity and the viscous f

31、orce are equal under stationary（稳态）conditions.,(3),Equation(3)may also be written,(4),m is the mass of the particle，v is the stationary setting velocity.,This equation has the following features（特点）:It is independent（无关）of particle shape;It assumes（假设）that the bulk density of the pure components app

32、lies to the setting units(i.e.no solvation（溶解）);It permits the evaluation of v for a situation in which the mass-friction-factor ration(m/f)is known;It permits the evaluation of(m/f)in a situation for which v is known.,Problems:For a aggregates（聚集体）or solvated lyophilic particles,the density of the

33、setting units is intermediated（居于中间）between the densities of the two pure components.Density for the setting particle?v is the function（函数）of(m/f),v shall be very small?,2.Stokess Law for Spheres,Distortion（形变）of flow streamlines（流线）around a spherical particle,It assumes（假设）that:The fluid is lamina（

34、层流）;The particle is a rigid（刚性的）sphere;The fluid is continuous（连续的）;No change of density and viscosity of the fluid.,Boundary（边界）conditions（条件）:The thickness（厚度）of each successive（连续的）layer（层）in the fluid is the infinitesimal mathematical increment dr;Velocity variation（变化）in the fluid can be descri

35、bed by dv/dr;When r=,the disturbing（扰动）influence of the particle has been damped away（消失）;When r=Rs,the velocity is zero.(nonslip没有滑动),The rate of energy dissipation（损耗）is,(5),The work（功）is done on the fluid by the particle is,(6),The force（力）acting on the fluid is given by Stokess Law,(7),3.Sedimen

36、tation Equation,For a spherical particle,the friction factor is given by f=6Rs(8),Based on equation(9)we can calculate v(Eq.10),Rs(Eq.11),m(Eq.12)and f(Eq.13).,Equation(3)becomes,(9),（10）,4.Effect of nonsphericity（非球形）and solvation（溶解）,In actual colloids the particlesin the case of,Polyhedron（多面体）So

37、lvated（溶解的）Asymmetrical（非对称的）,Equivalent sphere（等效球体）:A fictitious（虚拟的）particle with the same density as the unsolvated particle that with the same velocity as the experimental system.,Actual particles can deviate（产生偏差）from the Stokes model by being either solvated,asymmetrical or both,in which case

38、 f increases so that a particle of mass m will display a smaller sedimentation velocity than it would if it were an unsolvated sphere.,f/f0=(f/f*)(f*/f0)(14),f is the friction factor of the actual particle;f0 is the friction factor for an unsolvted sphere Given by Stokess Law(the lowest friction fac

39、tor);,The ratio f/f0 measures the amount by which the actual friction factor exceeds（超过）the minimum value;f*is the friction factor for a spherical particle having the same volume as the solvated particle of mass m;The ratio f*/f0 measures the increase in f due to solvation;The ratio f/f*measures the

40、 increase in f due to asymmetry.,5.Centrifugal sedimentation（离心沉降）,Ultracentrifuge（超级离心）The gravitational（重力）acceleration is increased by a factor of 105.The particle size that may be studied by sedimentation is decreased by the same factor.Ultracentrifuge has been used extensively for characterizat

41、ion（表征）of colloidal materials,such as proteins（蛋白质）,nucleic acids（核酸）and viruses（病毒）.,2.3 Diffusion（扩散）,C2 C1,Diffusion:A transport（运移）process of matter from a high-concentrationregion to a low-concentrationregion spontaneously.,Diffusion is the transport process of matter causedby the difference of

42、 concentrationwithout external（外加的）forces.,Fundamentally,it is the second law of thermodynamics that is responsible for the uniform（均匀的）distribution of matter at equilibrium since entropy（熵）is maximum when the molecules are distributed（分布）randomly throughout the space available to them.,It is same f

43、or colloidal particles.,1.Ficks first law,(20),Q the amount of material that flow through a cross section（截面）of area A.,J the flux（通量）of solute across A.,The amount of material that crosses A in a time interval t is,(21),Ficks first law equation,(22),D diffusion coefficient（扩散系数）of the solute.(m2 s-

44、1),D measures the diffusion ability of the solute.Negative mark present the solute migrates（迁移）from high-concentration region to low-concentration region.,Ficks first law gives the condition of diffusion will occur（发生）and the direction of the solute will migrate.Condition?Difference of concentration

45、.Direction?From high to low concentration region.,2.Ficks second law,(26),Conditions Consider the concentration changes that occur within a zone（区域）of cross section A,which has a thickness of x.It assume that the cross section is uniform throughout the compartment（单元）and that D is independent of sma

46、ll changes of concentration.,Ficks second law describes（表述）the change of concentration at a position in the direction of the solute migrate as a function of time.Ours interest:Focus our attention on the diffusion coefficient.From D we can get information of the size and shape of particles.D can be d

47、etermined in some experiments.,3.Diffusion coefficient and friction factor,Based on the analysis of the driving force underlying diffusion thermodynamically and the viscous force(resistance)act on the particles under stationary state condition,the velocity of diffusion of a particle is:,(30),kB is t

48、he Boltzmanns constant.,From the process of diffusion we know that the flux of matter through a cross section equals the product of its concentration and its diffusion velocity:,J=cvdiff,(31),Combine Equations(30)and(31)and comparing with Equation(22)lead to important result,(32),Gives the relation

49、between D and f.,It should be noted that this derivation(推导)contains no assumptions about the shape of the particles.When the particles are assumed to be spherical,the equation for diffusion coefficient will be,Stokes-Einstein relation,Equation(32)also point out the complementarity(互补性)between sedim

50、entation and diffusion measurement.For example:,(33),(34),s is the sedimentation coefficient of particle in acentrifugal field(Eq.(19).,Equations(33)and(34)show that diffusion studies combined with sedimentation studies,either under the force of gravity or in a centrifuge,yield information about par