1、Colloidal dispersion systemClassification of dispersed system based on particle sizeclassParticle sizeCharacteristics of systemexampleMolecular dispersionLess than 1 nmInvisible in electron microscope Pass through ultrafilter and semipermeable membrane undergo rapid diffusionOxygen molecules,ordinar
2、y ions,glucoseColloidal dispersionFrom 1 nm to o.5 mNot resolved by ordinary microscope(although may be detected under ultramicroscope)Visible in electron microscopePass though filter paperDo not pass semipermeable membrane Diffusion very slowly Colloidal silver sols,natural and synthetic polymers,c
3、heese,butter,jelly,milk,etc.Coarse dispersionGreater than o.5 mVisible under microscopeDo not passthough normal filter paper Do not dialyze though semipermeable menmbraneDo not diffusionGrains of sand,most pharmaceutical emulsions and suspension,red blood cellsTypes of Colloidal dispersion Lyophilic
4、 colloidsSystems containing colloidal particles that interact to an appreiable extent with the dispersion medium are referred to as lyophilic(solvent-loving)colloids.hydrophilic sols:gelatin,acacia,insulin,albuminLipophilic colloids:rubber,polystyrene.A material that forms a lyophilic colloidal syst
5、em in one liquid(e.g.water)may not do so in another liquid(e.g.benzene).Lyophobic colloidsLyophobic colloids is composed of materials that have little attraction.e.g.gold,silver,sulfur,arsenous sulfide,and silver iodide.The methods to prepare lyophobic colloids Dispersion methods 1,grinding method 2
6、,sonication dispersion method 3,arc discharge methodCondensation methods 1,physical methods 2,chemical methodsgrinding methodsonication dispersion methodarc discharge method Owing to the intense heat generated by the arc,some of the metal of the electrodes is dispersed as vapor,which condenses to fo
7、rm colloidal particles.Physical condensation methods1,replacement of solventPhysical condensation methods2,Steam quench methodchemical condensation methods 2H3AsO3（w）+3H2S As2S3（sol）+6H2O FeCl3（w）+3H2O（H）Fe(OH)3 （sol）+3HCl 2H2S(w）+SO2(g)2H2O+3S(sol）Na2S2O3+2HCl 2NaCl+H2O+SO2+S(sol)2HAuCl4+3HCHO+11KO
8、H 2Au(sol）+3HCOOK+8KCl+8H2O Sol purification 1,dialysis method 2,ultrafiltrationdialysis methodSemipermeable membranedialysis methodElectrodialysisultrafiltrationSemipermeable membraneultrafiltration Electro ultrafiltrationAssociation colloidsCMCthe critical micelle concentration(CMC)is defined as t
9、he concentration of surfactants above which micelles form and all additional surfactants added to the system go to micelles.Type of micelleCylindrical micelleBilayerBilayer vesicleInverted micelleMicrotubuleClassification and typical examples of association colloidsExampleType Compound Amphiphile Ge
10、genions Anionic Sodium lauryl sulfateCH3(CH2)11OSO3-Na+Cationic Cetyl trimethyl-ammonium bromideCH3(CH2)15N+(CH3)3Br-Nonionic Polyoxyethylene laury etherCH3(CH2)10CH2O(CH2OCH2)23HAmpholytic Dimenthyldodecy lammonio-propane sulfonateCH3(CH2)11N+(CH3)2(CH2)3OSO2-Properties of surface-active agents sho
11、wing changes that occur sharply at the CMCPredict the CMC of the mixture To determine the minimum amount of surfactantOptical properties of colloidsscattering of light Light scattering is a form of scattering in which light is the form of propagating energy which is scattered.Light scattering can be
12、 thought of as the deflection of a ray from a straight path,for example by irregularities in the propagation medium,particles,or in the interface between two media.The Faraday-Tyndall Effect When a strong beam of light is passed through a colloidal sol,a visible cone,resulting from the scattering of
13、 light by the colloidal particles,is formed.This is the Faraday-tyndall effect.Ultramicroscope An ultramicroscope is a microscope with a system of illumination that allows viewing of tiny particles.When the diameter of a particle is below or near the wavelength of visible light(around 500 nanometers
14、),the particle cannot be seen in a light microscope with the usual method of illumination.The ultramicroscope system is based on light scattering,not light reflection.UltramicroscopeElectron microscope Electron microscope,capable of yielding pictures of the actual particles,even those approaching mo
15、lecular dimensions,is now widely used to observe the size,shape,and structure of colloidal particles.Kinetic properties of colloids1,Thermally induced:Brownian movement,diffusion,osmosis.2,gravitationally induced:sedimentation3,applied externally:viscosityBrownian Motionthe random movement of colloi
16、dal partoclesThe first satisfactory theoretical treatment of Brownian motion was made by Albert Einstein in 1905.Diffusion Deduced by Einstein and StrokesWhere NA is Avogadros number,R is the gas constant,is the coefficient of viscosity of the surrounding medium,r is the radius of the spherical part
17、icle,T is the absolute temperature Diffusion is an entropy increasing process.D=RT6NAphrDiffusionOsmotic pressure Sedimentation In a gravitational field,heavy particles settle towards the foot of a column of solution by the process called sedimentation.When a solution is allowed to stand,a state of
18、equilibrium is finally reached when sedimentation and diffusion balance each other,that is,when in a given interval of time the amount of material which falls in the downward direction through a unit area is the same as that which diffuses upward because of the greater concentration at the lower lev
19、el.sedimentationdiffusionultracentrifugationM=RTSD(1-vr)Sedimentation is normally very slow,but it can be accelerated by ultracentrifugation,a technique that replaces the gravitational field with a centrifugal field.Where R is the gas constant,S is the sedimentation coefficient,the unit Svedberg is
20、1 X 10-13 second,T is the absolute temperature,D is the diffusion constant,v is the volume of 1 g of particle,is the density of medium.supercentrifugeViscosity Viscosity is en expression of the resistance to flow of a system under an applied stress.The more greater is the applied force required to m
21、ake it flow at a particular rate.Electrical Properties of ColloidsElectrokinetic PhenomenaElectrophoresisElectroosmosisSedimentation potentialStreaming potential ElectrophoresisElectroosmosisSedimentation potentialStreaming potentialStability of Colloid SystemsKinetic stability stableThermodinamic s
22、tability Lyophobic colloids unstable Lyophilic colloids stable Association colloids DLVO theoryEnergy（+）（-）Repulsion,VRComposite,VTPotential barrierInterparticle distancePrimary minimum(atrraction)Atrractive,VASecondary minimum(atrraction)Sensitization and Protective Colloidal Action The presence an
23、d magnitude,or absence,of a charge on a colloidal particle is an important factor in the stability of colloidal systems.Sensitization:the addition of a small amount of hydrophilic or hydrophobic colloid to a hydrophobic colloid of opposite charge tends to sensitize or even coagulate.Protection:the a
24、ddition of large amounts of hydrophile,however,stabilizes the system,the hydrophile being adsorbed on the hydrophobic particles.Sensitization protectionSolubilizationAn important property of association colloids in the solution is the ability of the micelles to increase the solubility of materials t
25、hat are normally insoluble,or only slightly soluble,in the dispersion medium used.The surface-active agent,if taken internally must be:1,nontoxic 2,miscible with the solvent3,compatible with the material to be solubilized4,free from disagreeable oder and taster5,relatively nonvolatileAssociation col
26、loidsDrug SolubilizationFactors affecting solubilization1,the chemistry of the surfactants2,the location of the drug in the micells 3,pH(nonionic surfactants)Tween 20Peppermint oilWater 010010001000505050Increasing quantity of waterPharmaceutical application of colloidsPharmaceutical application of
27、colloidsHydrogelsHydrogelsHydrogelsHydrogelsPharmaceutical application of colloidsMicroparticles1,carriers for vaccines and anticancer drugs2,reducing the uptake of the nanoparticles by the cells of the reticuloendothelial system3,enhance their uptake by the targeted cells4,the mucosal route of admi
28、nistrationPharmaceutical application of colloids Emulsions and microemulsionsEmulsions and microemulsions self-emulsifying drug delivery systems(SEDDS)Pharmaceutical application of colloidsLipidsomeLipidsomeThe industrialization production of liposome 1,manufacturing technique:film despersion method;solvent injection method.2,Particle size high-pressure homogenization machine 3,desolventizzazione vacuum distillation;spray drying;freeze drying;dialysis.4,remove the free drugs 5,sterilityPharmaceutical application of colloidsCommonly used polymeric drug carriers.
