胶体与界⾯化学a答案天津⼯业⼤学2011-2012学年第⼀学期应化、化⼯《胶体与界⾯化学》课程期末试卷(A卷)⼀、选择题（25分）1. 空⽓中直径0.01m的球形肥皂泡（表⾯张⼒为0.025N/m）所受附加压⼒为( D )(A) 2.5Pa (B) 5Pa (C) 10Pa (D) 20Pa2. 液体在⽑细管中上升的⾼度正⽐于（C ）。
(A) 温度(B) 液体密度(C) 附加压⼒(D) 管的半径3. 在相同温度下，同⼀液体被分散成有不同曲率半径的分散体系时，将具有不同饱和蒸⽓压，以P平、P凹、P凸分别表⽰平⾯、凹⾯和凸⾯液体上的饱和蒸⽓压，则三者的关系是（B ）(A) P平＞P凹＞P凸(B) P凸＞P平＞P凹(C) P凹＞P平＞P凸(D) P凸＞P凹＞P平4. ⽤最⼤⽓泡法测定溶液表⾯张⼒，对实际操作的规定哪条不正确？（D ）(A) ⽑细管必须严格清洗保证⼲净(B) ⽑细管⼝必须平整(C) ⽑细管应垂直放置并刚好与液⾯相切(D) ⽑细管垂直深深插⼊液体内部，每次浸⼊浓度尽是保持不变5. 表⾯活性剂是针对某种特定的液体或溶液⽽⾔的，表⾯活性剂的实质性作⽤是（ C ）（A）乳化作⽤（B）增溶作⽤（C）降低表⾯张⼒（D）增加表⾯张⼒6. 电动现象产⽣的基本原因是（D ）（A）外电场或外压⼒的作⽤（B）电解质离⼦的作⽤（C）分散相粒⼦或多孔固体的⽐表⾯能⾼（D）固体粒⼦或多孔固体表⾯与液相界⾯间存在扩散双电层结构7. 区别溶胶与真溶液和悬浮液最简单⽽灵敏的⽅法是（C ）（A）乳光计测定粒⼦浓度（B）超显微镜测定粒⼦⼤⼩（C）观察丁达尔效应（D）测定ζ电势8. 江、河⽔中含的泥沙悬浮物在出海⼝附近都会沉淀下来，原因有多种，其中与胶体化学有关的是（B ）（A）乳化作⽤（B）电解质聚沉作⽤（C）溶胶互沉作⽤（D）破乳作⽤9.雾属于分散体系，其分散介质是（A ）（A）⽓体；（B）液体；（C）固体；（D）⽓体或固体。
8. Surfaces and Interfaces8.1 IntroductionThere exist differences in the important parameters describing interfaces and surfaces:Surfaces Interfacesroughness composition conformation chain ends width (roughness) profile conformation fluctuationssnapshot of a coarse-grained moleculardynamics simulation of a block co-polymer double bilayer in waterGoundla Srinivas, IBM Almaden Research Centerthermodynamic: To allow contact between two different phases, an interface with a free energy between them is needed. Across this interface the intensive properties of the systems are changing from one phase to the other.Free energy of the interface ΔG = ΔW = 2σAA change of the interface requires a free energy ΔG, meaning a work ΔW, proportional to the area A and interfacial tension σ, is needed.work of cohesion W c = 2σwork of adhesion W c= σ1+σ2-σ12The process is assumed to be fully reversible.8.2 Polymer Surfaceair / vacuumpolymer surfacepolymer volume (bulk)Simple microscopic view: attractive forces between the atoms (spring-bead model) with force equilibrium in the volume, but missing partners at the surface→ attraction oriented towards the bulk→ surface tension / surface energy→ change of the structure at surfacea) Chain conformation in the vicinity of the surfaceComputer simulation: Structural properties of a dense polymer melt confined between two hard walls are investigated over a wide range of temperatures by dynamic Monte Carlo simulation using the bondfluctuation lattice model.The effect is present in a region close to the polymer surface. Deviation of the chain conformation is found in a region with an extension of ≈2R g .Baschnagel, Binder, Macromolecules 28, 6808 (1995)As the wall is further approached, the ability of the chains to reorient is progressively hindered, leading to an increase of R g|| and to a decrease of R g ⊥. Therefore the main effect of the wall is to reduce the orientational entropy of the polymers and to align them preferentially parallel to it.Experiments (GISANS): The samples consist of blend films of protonated and deuterated polystyrene (PS) spin coated onto glass substrates. A variation of the thickness of the blend films in a range of about 41 down to 0.66 times the radius of gyration R g of the chains in the bulk enables the determination of film thickness and confinement effects with the advanced scattering technique grazing incidence small angle neutron scattering (GISANS).The effect of the breaking of the translation symmetry by the presence of a surface is found in a more extended region of ≈8R g .Kraus et al., Europhys. Lett. 49, 210 (2000)The polymer molecule is altered in its conformation from an isotropic Gaussian chain (sphere) into an ellipsoidal shapechain segments are oriented in parallel to surfaceb) Chain end distribution Theory:Density of chain ends at the surface (de Gennes, 1992):φφρee N 2=with N length of chainφe number of ends at surfaceφ number of monomers per volume→ chain ends from a region 2R g are enriched in a layer of thickness d (typically 1-2 nm):N dae 2=ρ with segmental length aenrichment of chain ends at the surface due to entropic effects Experiments (NR): Mono-terminated polystyrenes (PS) are synthesized anionically to include a short perdeuteriostyrene sequence adjacent to the end groups for the purpose of selective contrast labeling of the end groups for neutron reflectivity (NR).The location of deuterium serves as a marker to indicate the location of the adjacent end group. Damped oscillatory end group concentration depth profiles at both the air and substrate interfaces are found. The periods of these oscillations correspond approximately to the polymer chain dimensions.contrast density depth profileKoberstein et al; Macromolecules 27,5341 (1994)c) Segment distribution in the vicinity of surfaceComputer simulation: Strong orientation of segments due to the breaking of the translational symmetry of the system by the presence of a surface. The effect is present in region close to surface only, with extension of ≈2R g.Experiments (Force balance): Strong modulation in the density in the vicinity of the surface (effect much more pronounced in case of a solid wall).transition region with significantly decreased densityd) Influence on the kineticsComputer simulation:At the polymer surface a very mobileand quasi-liquid layer is existing wellbelow a melting temperature T m. In thislayer the chain mobility is increased.at surface mobility in movement in parallel to the surface is increased in a thinlayer of thickness d (typically 2 nm)This behavior is similar to many crystal samples. The origin is the reduced number of entanglements at the surface.Experiments (FCS): Comparison of polymer diffusion, polyethyleneglycol (PEG), when adsorbed to a solid surface and in free solution(a) Flexible polymer chains that adsorb are nearly flat at dilute surface coverage (i.e., de Gennes pancake). The sticking energy for each segment is small, so no single segment is bound tightly, but the molecular sticking energy is large. (b) Diffusion coefficients (D) in dilute solution (blue circles) and at dilute coverage on a solid surface (red squares) plotted against the degree of polymerization (N) at 22°C.on surface: changed power law due to excluded volume statisticsDepending on the interaction between polymer and wall the mobility can by unchanged to bulk (neutral wall) or slowed down (attractive wall).How do polymer surfaces look in experiments?Examples:polystyrene machined titanium dual-acid-etched (DAE)titaniumSEMAFMNakamura et al, JDR 84, 515 (2005)Typically polymer surfaces are significantly smoother as compared to metal and metal oxide surfaces (independent of the surface treatment).PMDEGA after swelling in water vapor after 6 days storage in airZhong, PMB et al, Colloid. Polym. Sci. 289, 569 (2011)Homopolymer surfaces are only smooth with low surface roughness and good homogeneity if the homopolymer film is stable. If it is unstable the surface can roughen.If the polymer crystallizes a completely different polymer surface is observed. Due to the crystals present at the polymer surface, the surface roughness is significantly increased.8.3 Interface between polymerscase I: identical polymers A/A or compatible polymers A/B• interdiffusion of segments • adhesion • model of segment movementexample: PS/PS, PMMA/PMMA, PMMA/PVCcase II: incompatible polymers A/B• width of the interface in equilibrium • polymer-polymer interaction parameter (Flory-Huggins parameter) χexample: PS/PBrS, PS/PMMA, PS/PpMS, PS/PnBMAMathematical description of the interface:Rough interface j with mean z-coordinate set to zero and fluctuations in height z j (x)The rough interface can be replaced by an ensemble of smooth interfaces weighted by a probability density P j (φ)with a mean value ∫=dz z zP j j )(μand root-mean-square (rms) roughness ()∫−=dz z P z j j j )(22μσDifferent probability density function are possible and result in different interfaces: Normalized error-function (solid line) and hyperbolic-tangent (dashed line) have very similar refractive index profiles n j (z).Error function profile⎟⎟⎠⎞⎜⎜⎝⎛−−−+=++j j j j j j j z z erf n n n n z n σ222)(11 results from Gaussian probability density (μi =0) ⎟⎟⎠⎞⎜⎜⎝⎛−=222exp 21)(j jj z z P σσπand hyperbolic-tangent profile ⎟⎟⎠⎞⎜⎜⎝⎛−−−+=++j j j j j j j z z n n n n z n σπ32tanh 22)(11results from probability density (μi =0) ⎟⎟⎠⎞⎜⎜⎝⎛=−j jj z z P σπσπ32cosh 34)(2Both examples are based on symmetric probability functions, however, for real samples this symmetry is not ensured and thus asymmetric profiles can occur (e.g. polymer brush with exponential decay).a) Interface width of polymer interfacesComputer simulation (Monte-Carlo simulation by Binder, 1994):A symmetric binary mixture (polymer1, polymer2) below its critical temperature T c of unmixing is considered in a thin-film geometry confined between two parallel walls, where it is assumed that one wall prefers polymer1 and the other wall prefers polymer2. Then an interface between the coexisting unmixed phases is stabilized.with interface width χ6a L = yields rms-roughness πσ2L rms =only valid for smooth interfaces (σrmssmall) with qR g >1 and N →∞with segment length a scattering vector ()dq πλπ2sin 4=Θ=Not taking into account: - concentration dependence of χDifferent approximations in the framework of Mean Field theories:• Binder: expansion of free energy for φ=0.5 and N 1=N 2=N (with qR g >1 and χN>>1)()NaL 26−=χ• Brosetta: Integration of the quadratic gradient term in the vicinity of φ=0.5⎟⎠⎞⎜⎝⎛⎥⎦⎤⎢⎣⎡+−=21112ln 26N N aL χ• Stamm: minimization of the free energy using a "trial"-function⎟⎟⎠⎞⎜⎜⎝⎛⎥⎦⎤⎢⎣⎡+−=2121166N N aL πχ ⇒ It is possible to determine the polymer-polymer interaction parameter χ froma measurement of the interface width L, in case the degree of polymerization Nand the segment length a are known!• Frisch: modification of the profile on different length scales: deviation from the simple tanh-shapeb) entanglement density at the interface between two immiscible polymers The variation of entanglement density with interface width at an interface between two polymers is calculated using the relationships between chain packing and entanglement. The chain packing is obtained by the use of self-consistent mean-field techniques to calculate the average chain conformations within the interface region.calculated number of segmentsbetween entanglements as a functionof χassuming a bulk value of N e,typical for polystyrene, of 130Oslanec and Brown, Macromolecules 36, 5839 (2003)b) time dependent evolution of the interface widthHowever, all these models describe a time average and the final equilibrium interface. With experimental techniques it is possible to prepare interface between polymers far from equilibrium and to follow changes with time resolution.covering a large range of time and length scales the crossover between 4different regimes is observedt < τe: Rouse regimeτe < t < τf: Reptation regimeτf < t < τd: Blob movementτd < t: Fick diffusioncharacteristic power laws: tαRouse regime: α = 0.5Reptation regime: α = 0.25Fick Diffusion: α= 1.08.4 Rouse Model(P.E.Rouse 1953, extension B. Zimm 1956)The Rouse model describes the conformational dynamics of ideal chains. The main assumptions are: 1. no excluded volume interaction2. no hydrodynamic interactionTherefore one expects this model to work at Θ-condition or polymer melt condition.Polymers are interconnected objects with a large conformational entropy. As a consequence, the universal entropy-driven Rouse dynamics prevails at intermediate scales, where local potentials have ceased to be important and entanglements are not yet active. Key signature of the Rouse motion is the sublinear evolution of the segmental mean-square displacement2)(t2/1tr≈neutron spin echo (NSE) results on the single-chain dynamic structure factor: dynamics of poly(vinyl ethylene) on length scales covering Rouse dynamicsMean-square displacementof the protons, the solid linerepresents Rouse dynamicsRicher et al., Europhys. Lett., 66, 239(2004)Both molecular-dynamics (MD) simulations and MCT calculations on coarse-grained polymer models (bead and spring models)Bead-spring modelIn this model of a polymer molecule it consists of beads and springs forming a chain. The beads are hydrodynamics resistance sites that are dragged on by the suspending fluid. They also experience random Brownian forces caused by the thermal fluctuations in the fluid which are significant on the molecular scale. The spring is an entropic force pulling the adjacent beads together. In fact, the spring represents many monomer units that can coil and uncoil in response to the forces. This model is a reasonable representation of the polymer chain dynamics that actual polymer molecules undergo.8.5 Reptation Model(de Gennes, Doi, Edwards, 1971 + 1978)Reptation is the snake-like thermal motion of very long linear, entangled macromolecules in polymer melts or concentrated polymer solutions. It comprises:• entanglements with other chains hinder diffusion• each polymer chain is envisioned as occupying a tube of length L • movement of polymer chain is only possible within this fictive tube• special type of movement: diffusion only via movement of chain ends,keeping chain conformation unchangedtube diameter ddifferent types of movement:t < τe : no hindering in movement by tube (Rouse type movement)t = τe : density fluctuations within the chain are extended up to the length scale of the tube diameterτe < t < τf : polymer chain moves along the tubeτf < t < τd : chain starts to escape the tubet = τd : chain left the original tubet > τd : completely free movement of the chain with no remembering of the tubeExample:PE M w = 190k d = 49Å or PE M w = 17k d = 54ÅPS d ≈ 50ÅN R e , density ρ und temperature TInfluence on the interface profile:shown for different relative diffusion times t/t f 0.1 s mall →0.9 largeThe jump in the concentration profile is caused by the movement of the chain ends across the interface in the framework of the Reptation model.Attention: the profile needs to be convoluted with the tube diameter d8.6 Fick diffusionTranslation of the complete polymer chain is described as diffusion of the centerof masswith diffusion coefficient D Attention: different diffusion coefficients are existing D S self-diffusion coefficient (A moves in a matrix of A) D I inter-diffusions coefficient (A und B move with respect to each other) D T tracer-diffusion coefficient (marker T moves in matrix A)a) self-diffusion:Movement of chains in the identical environment → very difficult to detect experimentally, because no contrast between chain and environmentPossibility of marking individual chains (by deuteration or with fluorescent end-groups), but strictly this is a tracer experiment already Example: PS volume D S ≈4*10-14 cm 2/s thin film (300Å) D S ≈1.5*10-15 cm 2/s surface D S ≈9.3*10-16 cm 2/s⇒ slowing down of the diffusion due to the spatial confinementb) inter-diffusion:An interface between two polymers, which was prepared out of equilibrium (e.g. with the floating technique) is annealed above the glass transition temperature of both polymers→ broadening of the interface following the above arguments → late stages are caused by diffusion (t > τd )Experiment: X-ray- or neutron reflectivity measurementshydrogenated and deuterated polystyrene has been measured at 115 °C in-situ and in real time using NRdiffusion coefficientD = (1.7±0.2) × 10-17 cm 2/sBucknall et al., Macromolecules 32, 5453 (1999)• "fast-mode" theory B T B A A T A B I D N D N D ,,φφ+= • "slow-mode" theoryB T B A A T A B I D N D N D ,,111φφ+=Examples:Low molecular weight liquids D ≈10-6 cm 2/s polymers D ≈10-12-10-17 cm 2/s depending on temperaturec) tracer-diffusionusing small markers, e.g gold atoms in a well defined layered approachAnnealing the sample above the glass transition temperature of the polymer and probing the distances which the gold atoms had moved after defined times tReiter et al. Macromolecules 24, 1179 (1991)Dependence on molecular weight:Stamm et al., Macromolecules, 26, 2134 (1993)tracer-diffusions constant2−∝W T M D8.7 additional contributions to the interface widthIn addition to the width of the interface between two polymers which results from interdiffusion, contribution from other sources have to be taken into account. They arise from preparation: thickness variation of the filmwrinkles, dust particles, holes, impuritiesintrinsic: capillary wavesA capillary wave is a wave traveling along the phase boundary of a fluid, whose dynamics are dominated by the effects of surface tension. These waves are of thermal origin .Assuming a semi-infinite liquid with surface tension γLV a complex movement of the atoms makes a surface wavehaving a dispersion relation()g q q q LV rr r +=ργω32with ρ liquid density g Earth's accelerationSo thermal fluctuations cause a deviation from the ideal flat surface with an excess free energy density()()()()()Ζ⎥⎦⎤⎢⎣⎡ΖΔ+⎟⎠⎞⎜⎝⎛−Ζ∇+=Ζ∫∫22111d l P h A h fA L LV L exr r r γ ()()()()()Ζ⎥⎦⎤⎢⎣⎡Ζ+Ζ∇≈Ζ∫∫221d h P h A h f A L L LV L ex r r r γ yielding the height-height-autocorrelation function and power spectral density()Ζ=Ζr r c LV B q K Tk C 02)(πγ and 22214)(c LV LV B q q T k q L γγπ+=rwith K 0 modified Bessel function of zero ordercapillary waves can only be excited in an interval between λmin and λc for T>>0KA gravitation cut-off of the larges possible wavelength being excited isc c q πλ2=with LVc g q γρ=2 with the capillary length gLVργξ=being the lateral correlation length characteristic for the liquid (on the order of mm)and a short-range cut-off on the scale of the molecule diameter a is needed to avoid divergence of C(Ζ)a q 22maxmin ==πλ with a q π=maxExample: ethanol-vapor interface, σ=6.9 Åx-ray reflectivity and longitudinal diffuse scattering x-ray transverse diffuse scatteringSanyal et al.; Phys. Rev. Lett. 66, 628 (1991)Attention: in case of interfaces instead of surfaces the surface tension γLV is replaced by the interface tension γLL which is orders of magnitude smaller than the surface tension→ contribution of capillary waves to rms-roughness of interface increasedExample: Direct visual observation of thermal capillary waves at the free liquid-gas interface in a phase-separated colloid-polymer mixture imaged with laser scanning confocal microscopy (LSCM) at four different state points approaching the critical point(2004) each image is 17.5 μm by 85 μmAarts et al. Science 304,847Simple liquid → polymer:For highly viscous liquids and polymer melts the capillary waves are overdamped, their amplitude reduced.While, in general, both damped and propagating modes exist, for highly viscous polymers all modes are overdamped, which can be characterized solely by relaxation times τ.physical meaning of the over-damped relaxation timeconstantSinha, University of CaliforniaRoughness measurements are time averaged and cannot reveal the dynamic behavior of the waves.→ Need to probe the dynamics!Experiments: XPCSExample: capillary wave dynamics on glycerol surfaces investigated with XPCS performed at grazing anglesnormalized time correlation function22)()()()(ttt I t I t I g ττ+=described by exponential behavior1exp )(002+⎟⎟⎠⎞⎜⎜⎝⎛−=τττg g→ relaxation times τSeydel et al., Phys. Rev. B 63, 073409 (2001)The capillary wave is identified by its wave vector q and complex frequencyΓ+=i f p ωwhere the real part reflects the propagation frequency and the imaginary part the damping.At the transition from propagating to overdamped behavior f becomes purely imaginary; i.e., ωp =0.The transition from propagating (inelastic) to overdamped (quasielastic) behavior takes place at critical wave vector254ηργLV c q =with surface tension γLV , the dynamic viscosity η, and the density ρ of the polymerExample: Mixture of water and glycerol with 65% weight concentration of glycerolMadsen et al., Phys. Rev. Lett. 92, 096104 (2004)propagation frequency ωp (circles) and the dampingconstant Γ (squares) for the water -glycerol mixture at (a)30 °C and (b) 12 °C.8.8 Thin Film Preparation Techniques a) Solution-castingpreparation of thick polymer films (thickness from 100 nm to several μm)• polymer solution deposited on top of a horizontally oriented substrate• cover full substrate to have chance for uniform film if liquid is not spreading • solvent evaporates under controlled condition (T, p, atmosphere) → a solid film remains on the substrate→ allows for slow drying: films close to equilibrium can be preparedOn the scale of the capillary length the film at the substrate edges differs from the average film.Problems occur in case of pinning effects. If the contact line gets pinned during drying, no homogenous film is formed.Example: ternary blend PS, P αMS and PI cast from toluenePanagiotou, PhD Thesis TU Munich (2004)For complex fluids (highly viscous polymer solutions), the morphology is not determined by the evaporation process, the "coffee stain" effect but essentially by the capillary instabilities.Using the appropriate couple of polymer/solvent, a outward, inward or a lack of Marangoni flow in the droplets, leading to the formation of a rim, a drop or a uniform film, respectively, occurs.b) Spin-coatingpreparation of thin polymer films with thicknesses from 1 to 1000 nm• prepare polymer solution with desired concentration c • cover substrate entirely with polymer solution• select acceleration profile and spinning parameters (time, rotational speed) • start spin-coater after defined wait time → a solid film remains on the substrate→ due to non-equilibrium the film can have enrichment or lateral structuresDepending on rotational speed ω, concentration c, molecular weight Mw and apersonal parameter (wait time, person, machine)Attention: change in slope at entanglement concentration of solutionRuderer, PMB, Chem.Phys.Chem. 10, 664 (2009)Spin-coating is a complicated non-equilibrium processTheoretical description in the framework of a 3-step model (Lawrence, 1988) 1. step – start phasedeposition of solution with C 0 → strong height variationsacceleration of the substrate → most of the solution is flung-off the substrate → film thickness ≈100 μmEnd: Homogeneous film with thickness h 0 with concentration C 0 2. step – mass reduction by conventionevaporation can be neglected in comparison with the flow of solution towards to substrate edges → change of film thickness by convection2/102020341)(−⎟⎟⎠⎞⎜⎜⎝⎛+=t h h t h ηρω 3. step – evaporation of solvent through film surfaceevaporation rate of solvent larger than change in thickness by convection at a film thickness h w → mass reduction only by solvent evaporation, no polymer can leave the substrate anymore → dry, solid film remains()0,1s w f h h φ−=With the initial amount of solvent φs,0Polymer surface depends on the used solvent and on the spin-coating parameters:I: problems with solvents which have very high evaporation rate: → formation of skin on solution surface→ elastic film surface has a changed flow field of the confined polymer solution → hydrodynamic instabilities→ resulting lateral structures which have a star-shape with the center in the center of rotationII: problems with solvents which are hygroscopic and attract water from the surrounding, but are non miscible with water:→ demixing of both components (solvent and water) gives rise to lateral structuresMüller-Buschbaum et al.; Macromolecules 31, 3686 (1998)c) Floating-techniquepreparation of single and multiple polymer films (on non-wetable substrates)Schindler, Diploma Thesis TU Munich (2010)• scratch film with scalpel at 2 mm from substrate edge • put substrate into float box (tilt angle optimal at 10-15°) • add 2-3 drops of deionized water per second • remove substrate after film had decoupled• put second substrate with larger tilt angle into the water • fix polymer film on upper edge of this second substrate • remove water with 2-3 drops/sec • dry films (e.g. 4 h at 50°C)→ typically the needed time is 3-6 hours depending on the M w and film thickness→ not possible for all film thickness (thinner films are more difficult, integer number of R g can work), not possible for heat treated filmsProblems occur in case of wrinkle formation, incorporation of dust particles or trapping of water.Example: freely floating polymer film, tens of nanometers in thickness, wrinkles under the capillary force exerted by a drop of water placed on its surfaceThe wrinkling pattern is characterized by the number and length of the wrinkles.The PS film thickness h was varied from 31 to 233 nm. As the film is made thicker, the number of wrinkles N decreases (there are 111, 68, 49, and 31 wrinkles in these images).Huang et al.; Science 317, 650 (2007)d) Adsorption from solutiondeposition of single molecules, thin layers or thick films from solution with a controlled concentrationSketch:Adsorption is usually described through isotherms, that is, the amount of adsorbate on the adsorbent as a function of its pressure (if gas) or concentration (if liquid) at constant temperature.Isotherms are described bydifferent models:Langmuir isotherm (red) andBET isotherm (green)Computer simulation:Adsorption and self-assembly of linear polymers on smooth surfaces are studied using coarse-grained, bead-spring molecular models and Langevin dynamics computer simulations. The aim is to gain insight on atomic-force microscopy images of polymer films on mica surfaces, adsorbed from dilute solution following a good-solvent to bad-solvent quenching procedure.Chremos et al., Soft Matter5, 637 (2009)Molecular Weight Competition: Upon initial mixing of a formulation, all chains attempt to adsorb on a surface. For adsorbing homopolymers, thermodynamics dictates a preference for adsorption of long chains, and so short chains, originally adsorbed, are displaced form the surface at longer times.Santore+ Fu, Macromolecules 30, 8516 (1997)Fu + Santore, Macromolecules 31, 7014 (1998) Large scale industrial applications involving substantial quantities of complex fluids such as paints, inks, and coatings employ water soluble polymers with a broad distribution of molecular weights: The likelihood that some fraction of the added chains impart the desired interfacial properties means that changes in molecular weight distribution from batch to batch can dramatically impact the properties of a formulation.Experiments: Adsorption of polymers is very common in case of polyeletrolytes and used to build up multi-layers.Layer-by-Layer (LBL) assembly: fabrication of multilayers by consecutive adsorption of polyanions and polycationsDecher et al.; Science 277, 1232 (1997)Fine-tuning the film thickness by ionic strength (addition of salt yields thicker layers; polyanion from salt, polycation from pure water)Decher + Schmitt, Progr. Colloid Polym. Sci. 89, 160 (1992) A small list of polyions already used for multilayer fabrication:e) Spray coatingdeposition of thick films from solution with a controlled concentration, depending on deposition conditions (wet droplets = spraying, dry polymer = airbrush)control parameters: number of depositions, deposition time, solvent, polymer concentration, distance nozzle-surface。
表面活性剂化学期末考试题HEN system office room 【HEN16H-HENS2AHENS8Q8-HENH1688】（2011—2012）学年08C班第Ⅰ学期表面活性剂期末考试题A 姓名：班级：学号：成绩：1. 表面活性剂2. 临界胶束浓度3. 浊点4. 两性表面活性剂二、选择题. (15×3分)A.非离子型的毒性大于离子型，两性型毒性最小值越小，亲水性越强C.做乳化剂使用时，浓度应大于CMCD.做O/W型乳化剂使用，HLB值应大于82. 对表面活性剂的叙述正确的是（）A.根据经验，表面活性剂的HLB值范围限定在0-20之间B.表面活性剂不能混合使用C.聚氧乙烯基团的比值增加，亲水性降低D.杀精避孕套中起杀精作用的主成分壬基酚聚氧乙烯醚可作洗涤剂3.等量的Span -80与吐温-80混合后的HLB值是（）A.4.34.表面活性剂性质不包括（）A.亲水亲油平衡值值 C. 适宜的粘稠度 D. Krafft点5. 下列说法正确的是（）A. krafft点越低，该表面活性剂低温水溶性越好B.非离子表面活性剂应该在浊点以上使用C.疏水基为直链的比带支链的难于降解D.含有芳香基的表面活性剂比仅含有脂肪基的表面活性剂易于降解，故洗衣粉中主成分为十二烷基苯磺酸钠6. 下列说法不正确的是（）A.胶束越大，对于增溶到胶束内部的物质增溶量越大B.乳状液类型通常有O/W,W/O,套圈型三种。
C. 阳离子表面活性剂不能做破乳剂D. 玻璃器皿中易得到O/W型乳状液7. 下列叙述不正确的是（）A.聚乙烯醇，聚丙烯酰胺为高分子表面活性剂B.非离子型表面活性剂的性能都优于离子型表面活性剂C.离子型表面活性剂存在Krafft点，非离子表面活性剂存在浊点D.一般分子量较大的表面活性剂洗涤、分散、乳化性能好，分子量小的润湿、渗透性能好8.下列说法不正确的是（）A.液体油污的去除主要是靠表面活性剂的增容作用而实现的B.非离子表面活性剂不宜用于洗涤天然棉纤维C.烷基苯磺酰二乙醇胺可做稳泡剂D.纯十二烷基苯磺酸钠是很好的起泡剂9.下列说法正确的是（）A.餐具洗涤剂可以用来洗涤瓜、果、蔬菜、肉B.洗发香波的主要成分为十八烷基苯磺酸钠及烷基酰醇胺C.重垢液体洗涤剂表面活性剂含量一般在80%以上D.粉状洗涤剂和液体洗涤剂中表面活性剂主成分完全不同10.下列说法中不正确的是（）A.只有阳离子表面活性剂具有良好的杀菌消毒作用B.分子结构中含有苄基的季胺盐具有较强的杀菌性C.药物中引入磺酸基后易被人体吸收，并提高水溶性，而药理作用改变不大D.烷基苯磺酸钠通常为黄色油状液体11.下列说法正确的是（）A.阳离子表面活性剂主要是含氮的有机胺衍生物B.阳离子表面活性剂不存在Krafft点C.阳离子表面活性剂不可做相转移催化剂D.两性表面活性剂没有等电点12.下列关于两性表面活性剂性质不正确的是（）A.具有等电点B.临界胶束浓度随着溶液pH值的增加而增大C.两性表面活性剂没有Krafft点，但有浊点。
