Effects of surfactants on emulsification and secondary structure of lysozyme in aqueous solutions

Disperse SystemsThis chapter includes the main types of liquid preparations containing undissolved or immiscible drugs distributed throughout a vehicle.In these preparations,the substance distributed is referred to as the dispersed phase,and the vehicle is termed the dispersing phase or dispersion medium.Together,alley produce a dispersed system.本章包括分布在整个介质中的含有不溶解或不混溶药物的主要类型的液体制剂。

在这些制剂中，所分配的物质被称为分散相，并且该载体被称为分散相或分散介质。

分散系统。

The particles of the dispersed phase are usually solid materials that are insoluble i n the dispersion medium.In the case of emulsions,the dispersed phase is a liquid th at is neither soluble nor miscible with the liquid of the dispersing phase.Emulsificati on results in the dispersion of liquid drug as fine droplets throughout the dispersing phase.In the case of an aerosol,the dispersed phase may be small air bubbles throu ghout a solution or an emulsion.Dispersions also consist of droplets of a liquid(solu tion or suspension)in air.分散相的颗粒通常是不溶于分散介质的固体材料。

Physical and chemical properties ofsurfactantsSurfactants are versatile compounds that have numerous applications in industries such as detergents, toiletries, and food, to name a few. These compounds are unique in that they possess both hydrophilic and hydrophobic properties, allowing them to interact with both water and oil-based substances. In this article, we will explore the physical and chemical properties of surfactants and how they contribute to their functionality.Physical PropertiesSurface TensionOne of the most significant physical properties of surfactants is their ability to reduce surface tension. Surface tension is the force that holds the surface of a liquid together. As a result, surfactants are commonly used in detergents and soaps to help remove oil and dirt from surfaces by breaking down the surface tension of the water.Critical Micelle ConcentrationSurfactants also exhibit a critical micelle concentration (CMC), which is the concentration at which the molecules of the surfactant start to aggregate in water to form micelles. Micelles are tiny clusters of surfactant molecules that surround oil droplets, allowing them to be suspended in water. The ability of surfactants to form micelles is crucial for their effectiveness as emulsifying agents.Wetting PropertiesSurfactants also exhibit wetting properties. Wettability refers to the ability of a liquid to spread over a surface. Surfactants enhance wettability by lowering the contact angle between the liquid and the surface. This property is essential in many industries, including agriculture, where surfactants are used to increase the effectiveness of pesticides and herbicides by spreading them evenly over plant surfaces.Foaming PropertiesAnother physical property of surfactants is their ability to form stable foam. The ability to form foam is useful in industries such as food, where surfactants are added to increase the volume of whipped cream or to allow carbonated drinks to maintain their fizziness.Chemical PropertiesHydrophilic/Lipophilic BalanceThe chemical structure of surfactants is crucial to their ability to interact with water and oil. Surfactants typically have two distinct parts: a polar hydrophilic head and a nonpolar hydrophobic tail. The balance between these two parts is referred to as the hydrophilic/lipophilic balance (HLB). The HLB determines the effectiveness of surfactants in emulsifying oils in water or water in oils.Cationic, Anionic, Nonionic, and AmphotericSurfactants can also be classified based on their electric charge. Cationic surfactants have a positive electric charge and are commonly used as disinfectants and fabric softeners. Anionic surfactants have a negative electric charge and are common in detergents and cleaning products. Nonionic surfactants have no electric charge and are used in products such as shampoos and facial cleansers. Amphoteric surfactants can have both a positive and negative electric charge and are used in products such as body washes and toothpaste.Degradability and ToxicityEnvironmental concerns about surfactants have led to an emphasis on the biodegradability and toxicity of surfactants. Many surfactants are biodegradable, meaning they can be broken down by natural processes. However, some surfactants are not biodegradable and can persist in the environment, potentially causing harm to wildlife. As a result, many industries are working to develop surfactants that are both effective and environmentally friendly.ConclusionSurfactants are crucial compounds with numerous applications in various industries. Their unique physical and chemical properties allow them to interact with both water and oil-based substances effectively. Understanding the physical and chemical properties of surfactants is crucial in developing a range of surfactant-based products that are both effective and environmentally friendly.。

脾、肾。

根据“缓则治其本”、“上下交病治其中”的原则,治以健脾益气,培补中气为大法。

使中焦脾胃得运,脾健以使内伏痰瘀之宿根渐化,扶助正气,以防止小儿哮喘的复发。

参考文献[1]　潘桂娟,金香兰.论痰浊与衰老[J].中国中医基础医学杂志,1997,3(5):62.[2]　夏永良,王卉,李德新.论脾统四脏[J].中国中医基础医学杂志,2001,7(10)69-71.(本文编辑:林榕　校对:林榕　于晓婷)论 著先天性白内障手术治疗及术后视功能训练的研究Resear ch of Oper ation Tr eatment f or Congenital Cataract and Postoper ative Visual Function Tr aining温克征　刘晶　李丹　万晓宁　胡毅作者单位:110015　沈阳,辽宁省残疾儿童康复中心(温克征　刘晶　李丹　万晓宁　胡毅) 【摘要】　目的　评价先天性白内障超声乳化手术治疗联合视功能锻炼的疗效。

方法　对于30例(48眼)视力不同的先天性白内障患儿进行白内障超声乳化吸出联合人工晶体植入术,术后进行视功能康复。

观察术后2周及1年视力、融合功能、立体视觉恢复情况。

结果　术后2周视力均分别比术前视力显著提高(P<0.01),术后1年矫正视力≥0.3者占83.3%,矫正视力≥0.05者占100%,具有融合功能和立体视觉者分别占39.6%,18.8%。

结论　先天性白内障超声乳化吸出联合人工晶体植入,手术切口小,组织损伤小,术后进行视功能训练,近期手术疗效显著。

【关键词】　先天性白内障;超声乳化吸出术;人工晶体植入术;视功能　 【中图分类法】　R776.1　【文献标识码】　A 文章编号:1001-1358(2007)01-005-02 Ab str act:Obj ect ive T o evaluat e t herapeut ic effects of ult rasound emul sificat ion suct ion an d post oper at ive v is ual function exercis e for congenit al cat ar act.Met hods30ch ildren(48eyes)s uffering from congenit al cat aract wit h eyes ight dysfunct ion received ul t ras ound em uls ificat ion s uct ion t oget h er wit h int raocul ar len s impl ant at ion an d post oper at ive v is ual function exercis e.T he eyesigh t,fu sion funct ion and st er eovision were observed aft er2weeks and1year aft er operat ion.R esul t s T he eyesigh t of chil dren was s ignificant ly improved aft er operat ion(P<0.01).Th e eyes of correct ed vis ion exceeding0.3and0.05aft er1year account ed for83.3%,100%, respect ively.Th e eyes wit h fusion funct ion and s t ereov is ion account ed for39.6%,18.8%,res pect ively.Concl usions Ul t ras ound em uls ificat ion suction t oget her wit h int raocular lens impl ant at io n has t he advant age of s mall incis ion and l it tl e tis sue damage.After post operat ive visu al function exercise,t herapeut ic effect s are great in a s hort t erm.Key word:Congen ital cat aract;Ult rasoun d emul sificat io n s uct ion;Intr aocu lar l ens im plant at ion;Visual fu nct ion. 先天性白内障是儿童常见致盲眼病,流行病学显示其患病率为0.6～6/10000,新生儿发病率为2.2～2.49/ 10000[1],先天性白内障手术治疗及术后视功能训练,对患儿有用视力的恢复有重要的临床意义。

Effect of Surfactants on the Interfacial Tension and Emulsion Formation between Water and Carbon Dioxide Sandro R.P.da Rocha,Kristi L.Harrison,and Keith P.Johnston*Department of Chemical Engineering,University of Texas,Austin,Texas78712Received July8,1998.In Final Form:October7,1998 The lowering of the interfacial tension(γ)between water and carbon dioxide by various classes of surfactants is reported and used to interpret complementary measurements of the capacity,stability,and average drop size of water-in-CO2emulsions.γis lowered from∼20to∼2mN/m for the best poly(propylene oxide)-b-poly(ethylene oxide)-b-poly(propylene oxide)(PPO-b-PEO-b-PPO)and PEO-b-PPO-b-PEO Pluronic triblock copolymers,1.4mN/m for a poly(butylene oxide)-b-PEO copolymer,0.8mN/m for a perfluoropolyether (PFPE)ammonium carboxylate and0.2mN/m for PDMS24-g-EO22.The hydrophilic-CO2-philic balance (HCB)of the triblock Pluronic and PDMS-g-PEO-PPO surfactants is characterized by the CO2-to-water distribution coefficient and“V-shaped”plots of logγvs wt%EO.A minimum inγis observed for the optimum HCB.As the CO2-philicity of the surfactant tail is increased,the molecular weight of the hydrophilic segment increases for an optimum HCB.The stronger interactions on both sides of the interface lead to a lowerγ.Consequently,more water was emulsified for the PDMS-based copolymers than either the PPO-or PBO-based copolymers.IntroductionSupercritical fluid(SCF)carbon dioxide(T c)31°C,P c )73.8bar)is an environmentally benign alternative to organic solvents for waste minimization.It is nontoxic, nonflammable,and inexpensive.However,because of its very low dielectric constant, ,and polarizability per volume,R/v,CO2is a poor solvent for most nonvolatile lipophilic and hydrophilic solutes.1It may be considered a third type of condensed phase,different from lipophilic and hydrophilic phases.Consequently,it is possible to disperse either lipophilic or hydrophilic phases into CO2, in the form of microemulsions,emulsions,and latexes, given an appropriate surfactant.Because of the low values of and R/v for CO2,the most CO2-philic types of functional groups have low cohesive energy densities,e.g.,fluoro-carbons,fluoroethers,and siloxanes.2-6The solvent strength of carbon dioxide may be understood by the fact that the solubility of a polymer in carbon dioxide is highly correlated with the surface tension of the pure polymer melt.7For example,poly(fluoroacrylates)with low surface tensions of10-15mN/m are highly soluble,whereas poly-(dimethylsiloxanes)with surface tensions of20mN/m are moderately soluble,and hydrocarbon polymers with higher surface tensions show very low solubility.For nonpolar or slightly polar polymers,the surface tension is a measure of the van der Waals forces and is related to the cohesive energy density.Because R/v is so small for CO2,polymers with low cohesive densities and surface tensions are the most soluble.The first generation of research involving surfactants in SCFs addressed reverse micelles and water-in-SCF microemulsions,for fluids such as ethane and propane8,9 as reviewed recently.10,11Microemulsions are thermody-namically stable and optically transparent,with typical droplet diameters of about2-10nm.The mechanistic insight gained from these studies of phase equilibria, interfacial curvature,and droplet interactions in a su-percritical fluid is directly applicable to carbon dioxide. Attempts to form water-in-CO2(w/c)microemulsions have been elusive.6,12,13For PFPE COO-NH4+w/c microemul-sions,FTIR,UV-visible absorbance,fluorescence,and electron paramagnetic resonance(EPR)experiments have demonstrated the existence of an aqueous domain in CO2 with a polarity approaching that of bulk water,14as has also been shown by small-angle neutron scattering (SANS).15Organic-in-CO2microemulsions have also been formed for600molecular weight poly(ethylene glycol) (PEG600)and for polystyrene oligomers.16,17In many previous studies,surfactant activity in CO2has been characterized in terms of water uptake into a CO2 microemulsion.Since the results were negative most of the time,it has been difficult to determine how to design surfactants to the water-CO2interface.A more direct property,such as the interfacial tension,is needed to understand the activity of surfactants at various interfaces containing carbon dioxide.In SCF systems,only a few studies have measured the interfacial tension(γ)even for simple binary systems(1)O’Shea,K.;Kirmse,K.;Fox,M.A.;Johnston,K.P.J.Phys.Chem. 1991,95,7863.(2)McHugh,M.A.;Krukonis,V.J.Supercritical Fluid Extraction: Priciples and Practice,2nd ed.;Butterworth:Stonham,MA,1994.(3)Hoefling,T.A.;Newman,D.A.;Enick,R.M.;Beckman,E.J.J. Supercrit.Fluids1993,6,165-171.(4)Newman,D.A.;Hoefling,T.A.;Beitle,R.R.;Beckman,E.J.; Enick,R.M.J.Supercrit.Fluids1993,6,205-210.(5)DeSimone,J.M.;Guan,Z.;Elsbernd,C.S.Science1992,257, 945.(6)Harrison,K.;Goveas,J.;Johnston,K.P.;O’Rear,ngmuir 1994,10,3536.(7)O’Neill,M.L.;Cao,Q.;Fang,M.;Johnston,K.P.;Wilkinson,S. P.;Smith,C.D.;Kerschner,J.;Jureller,S.Ind.Chem.Eng.Res.1998, 37,3067-3079.(8)Fulton,J.L.;Smith,R.D.J.Phys.Chem.1988,92,2903-2907.(9)Johnston,K.P.;McFann,G.;Lemert,R.M.Am.Chem.Soc.Symp. Ser.1989,406,140-164.(10)Bartscherer,K.A.;Minier,M.;Renon,H.Fluid Phase Equilib. 1995,107,93-150.(11)McFann,G.J.;Johnston,K.P.In Microemulsions:Fundamental and Applied Aspects;Kumar,P.,Ed.;Dekker:New York,1998;Vol.in press.(12)Iezzi,A.;Enick,R.;Brady,J.Am.Chem.Soc.Symp.Ser.1989, No.406,122-139.(13)Consani,K.A.;Smith,R.D.J.Supercrit.Fluids1990,3,51-65.(14)Johnston,K.P.;Harrison,K.L.;Clarke,M.J.;Howdle,S.M.; Heitz,M.P.;Bright,F.V.;Carlier,C.;Randolph,T.W.Science1996, 271,624-626.(15)Zielinski,R.G.;Kline,S.R.;Kaler,E.W.;Rosov,ngmuir 1997,13,3934-3937.419Langmuir1999,15,419-428including carbon dioxide and a liquid phase.18-20None of these studies included a surfactant.Surfactants have been studied for the generation of CO2foams in water21typically for water-soluble surfactants.The effects of various surfactants on theγbetween supercritical CO2and PEG (600MW)were reported recently.16At276bar,the addition of1%PFPE COO-NH4+reducesγfrom3.2to2.1mN/m, and the interfacial area of the surfactant is437Å2/ molecule.Interfacial tension measurements have also been made between poly(2-ethylhexyl acrylate)(PEHA)and CO222and styrene oligomers and CO2.23As is well-known for water-in-oil(w/o)emulsions and microemulsions,the phase behavior,γ,and curvature are interrelated,as shown in Figure1.24A minimum inγis observed at the phase inversion point where the system is balanced with respect to the partitioning of the surfactant between the phases.25,26Upon change of any of the formulation variables away from this point,for example,the temperature or the hydrophilicity/hydro-phobicity ratio(in our case the hydrophilic/CO2-philic ratio),the surfactant will migrate toward one of the phases. This phase usually becomes the external phase,according to the Bancroft rule.27Unlike the case for conventional solvents,a small change in pressure or temperature can have a large influence on the density and thus on the solvent strength of a supercritical fluid.By“tuning”the interactions between the surfactant tail and the solvent,it becomes possible to manipulate the phase behavior,and therefore the activity of the surfactant at the interface and curvature,and also the extension of the surfactant tails.As an example of pressure tuning,a water-in-propane microemulsion is inverted to a propane-in-water microemulsion by varying the pressure by50bar in the C12EO6/brine/propane system, at constant temperature.28This system undergoes a phase inversion density,by analogy with the phase inversion temperature,for conventional systems.If the density is changed so that the surfactant prefers either phase over the other,the surfactant is less interfacially active and γincreases.16,22,23The objective of this study is to achieve a fundamental understanding of the lowering of the water-CO2inter-facial tension by different classes of surfactants and to use this knowledge to explain the formation and stability of water-in-CO2(w/c)emulsions.The surfactants include PFPE COO-NH4+,Pluronic R(PPO-b-PEO-b-PPO)and Pluronic L(PEO-b-PPO-b-PEO)triblock copolymers,poly-(butylene oxide-b-ethylene oxide)(PBO-b-PEO),and poly-(dimethylsiloxane)(PDMS)copolymers with PEO-PPO grafts(PDMS-g-PEO-PPO).Fromγmeasurements ver-sus concentration,the adsorption is investigated for PFPE COO-NH4+and used to determine the critical micro-emulsion concentration.For the PPO-and PDMS-based surfactants,the concept of a hydrophilic-CO2-philic bal-ance(HCB)is introduced by relatingγand the distribution coefficient of the surfactant to the EO fraction(see Figure 1).To understand howγand the HCB influence colloid stability,we chose to study w/c emulsions in contrast to previous studies of microemulsions,since so few of these surfactants form microemulsions.Emulsions are ther-modynamically unstable,but may be kinetically stable, with droplets from100nm to several micrometers in diameter.The presence of the surfactant at the interface lowers theγand thus the Laplace pressure,reducing the energy necessary to deform the interface.29The emulsions may be stabilized against flocculation due to van der Waals forces by steric stabilization,as has been analyzed theoretically,30-33and/or Marangoni stresses,due to gradients in interfacial tension at the interface.To characterize emulsion capacity,stability,and the average droplet size of the emulsions,an in-situ turbidity technique has been applied in addition to visual observations.The ability to design surfactants for the interface between CO2 and an aqueous phase based upon knowledge of the relationship between colloid formation and stability,phase behavior,andγis of interest for a wide variety of heterogeneous reactions and separation processes in CO2. Examples include dry cleaning,extraction with micro-(16)Harrison,K.L.;Johnston,K.P.;Sanchez,ngmuir1996, 12,2637-2644.(17)McClain,J.B.;Betts,D.E.;Canelas,D.A.;Samulski,E.T.; DeSimone,J.M.;Londono,J.D.;Cochran,H.D.;Wignall,G.D.;Chillura-Martino,D.;Triolo,R.Science1996,274,2049.(18)Heurer,G.Ph.D.Thesis,The University of Texas at Austin, 1957.(19)Chun,B.-S.;Wilkinson,G.T.Ind.Eng.Chem.Res.1995,34, 4371-4377.(20)Schiemann,H.;Wiedner,E.;Peter,S.J.Supercrit.Fluids1993, 6,181-189.(21)Lee,H.O.;Heller,J.P.;Hoefer,A.M.W.SPE Reservoir Eng. 1991,11,421-428.(22)O’Neill,M.;Yates,M.Z.;Harrison,K.L.;Johnston,P.K.;Canelas,D.A.;Betts,D.E.;DeSimone,J.M.;Wilkinson,S.P.Macromolecules1997,30,5050-5059.(23)Harrison,K.L.;da Rocha,S.R.P.;Yates,M.Z.;Johnston,K. P.;Canelas,D.;DeSimone,ngmuir1998,14,6855-6863.(24)Aveyard,R.;Binks,B.P.;Clark,S.;Fletcher,P.D.I.J.Chem. Technol.Biotechnol.1990,48,161-171.(25)Bourrel,M.;Schechter,R.S.Microemulsions and Related Systems:Formulation,Solvency and Physical Properties;Marcel(27)Ruckentein,ngmuir1996,12,6351-6353.(28)McFann,G.J.;Johnston,ngmuir1993,9,2942.(29)Walstra,P.Chem.Eng.Sci.1993,48,333-349.(30)Peck,D.G.;Johnston,K.P.Macromolecules1993,26,1537.(31)Meredith,J.C.;Johnston,K.P.Macromolecules1998,31,5507-5555.(32)Meredith,J.C.;Sanchez,I.C.;Johnston,K.P.;Pablo,J.J.d.Figure1.Schematic representation of phase behavior andinterfacial tension for mixtures of water,CO2,and nonionicsurfactants as a function of formulation variables.420Langmuir,Vol.15,No.2,1999da Rocha et al.emulsions and emulsions,phase transfer reactions,34,35and emulsion polymerization.36Experimental SectionMaterials.All of the surfactants were used as received,unless indicated.The CF 3O(CF 2CF(CF 3)O)∼3CF 2COO -NH 4+(PFPE COO -NH 4+),a gift from A.Chittofrati,37was stored in a desiccator.The single tail Krytox-sulfate,R -COOCH 2CH 2OSO 3--Na +,where R )CF 3(CF 2CF(CF 3)O)n CF 2CF 2-,and the triple tail Krytox-sorbitol surfactants were synthesized by E.Singley and Dr.E.J.Beckman at the University of Pittsburgh.38Pluronic L,PEO-b -PPO-b -PEO (PEO -PPO -PEO),and Pluronic R,PPO-b -PEO-b -PPO (PPO -PEO -PPO),surfactants were a gift from BASF.The block copolymer PEO-b -PBO (EO 15-BO 12,SAM185)(where the subscripts indicate the number of repeat units of each moiety)was provided by Pittsburgh Paint and Glass.The surfactant (CH 3)3SiO[Si(CH 3)2O]20[Si(CH 3)(R)]2OSi(CH 3)3,with graft R )(CH 2)3O(C 2H 4O)∼11H,(PDMS 24-g -EO 22),M w ∼2600,was a gift synthesized by Unilever.7SILWET L-7500(M w )3000),(CH 3)3SiO(Si(CH 3)2O)x (Si(CH 3)(R))y OSi(CH 3)3,with R )(CH 2)3O-(C 3H 6O)n Bu (PDMS 11-g -PO 39),with n ,x ,and y not specified,and SILWET L-7622(M w )10000),with a similar backbone,but R )(CH 2)3O(C 2H 4O)m Me (PDMS 105-g -EO 68),were provided by OSi Specialties,Inc.ABIL B 8851(M w ∼6000),(CH 3)3SiO(Si-(CH 3)2O)22(Si(CH 3)(R)O)4Si(CH 3)3,with R )(CH 2)3O(C 2H 4O)∼17-(C 3H 6O)∼4H (PDMS 28-g -EO 67-PO 17),and ABIL B 88184(M w ∼13000),(CH 3)3SiO(Si(CH 3)2O)73(Si(CH 3)(R)O)4Si(CH 3)3,with R ∼(CH 2)3O(C 2H 4O)∼32(C 3H 6O)∼7H (PDMS 79-g -EO 126-PO 28)were obtained from Goldschmidt AG.PDMS homopolymer with a M w of 13000was synthesized by J.M.DeSimone at U.N.Carolina.Poly(ethylene glycol)with a molecular weight of 600was obtained from Polysciences,Inc.Poly(butylene glycol)monoether,composed of an ethylene oxide backbone with an ethyl side group (PBO,800g/mol)was supplied by Air Products.Poly(propylene glycol)(1025g/mol)was obtained from Polysciences,Inc.,and used as received.Deionized water (NANOpureII;Barnstead)and instrument grade carbon dioxide (99.99%)were used for all experiments.Phase Behavior.Phase boundaries were determined in the variable-volume view cell as described in further detail else-where.7For a given weight of surfactant and CO 2,the pressure of the system was increased until a single phase was observed in the view cell.The pressure was then decreased slowly until the solution became slightly turbid.The pressure was then increased again,and the process was repeated.The pressure where the system became turbid was classified as the cloud point pressure.The pressure and temperature were measured to (0.2bar and (0.1°C,respectively.Interfacial Tension Measurements.The tandem variable-volume pendant drop tensiometer described previously 16was used to measure the interfacial tension between CO and water (γ).The apparatus consisted of two variable volume view cells (the drop phase cell and the measurement cell (continuous phase cell)),an optical rail for proper alignment,a light source,a video camera,and a computer.The drop phase cell contained water saturated with an excess amount of pure CO 2,and the continuous phase cell contained CO 2and surfactant (if present).In this configuration,the surfactant only has to diffuse short distances in the small volume of the droplet phase.Pendant drops were formed on the end of a stainless steel or PEEK capillary tube with an inside diameter ranging from 0.01to 0.03in.Once a suitable drop was formed,the six-port switching valve connecting the two cells was closed and timing of the drop age was started.Several images were recorded as a function of drop age.Images of the drop were obtained in a tagged imagefile format (TIFF)and the edge of the drop was extracted from data at various global threshold values using a C ++program.From the shape of the interface,the γmay be obtained from the Laplace equationwhere ∆P is the pressure differential across the interface,R 0is the radius of curvature at the apex of the drop,and z is the vertical distance from the apex.A set of three first-order differential equations was used to express Laplace’s equation,and a computer program 39,40was used to solve for γ.The density difference between the two phases was calculated by using an equation of state for pure CO 241and steam tables for pure water.The aqueous phase density was assumed to change less than 0.0025g/cm 3for the concentrations of surfactant studied.Emulsion Formation,Stability,and Average Droplet Size Estimation.Figure 2shows a schematic representation of the experimental apparatus,similar to a previous version,for turbidimetric measurement and visual observation of emulsion formation and stability.22The system consists of a 28-mL variable-volume view cell,an optical cell (0.1cm path length)which was mounted in a spectrophotometer (Cary 3E UV -vis),a high-pressure reciprocating pump (minipump with a flow rate of 8-80mL/min),and a manual pressure generator (High-Pressure Equip.,model 87-6-5).A six-port switching valve (Valco Instru-ments Co.,Inc.)with an external sampling loop was used to add water to the system.The pressure was monitored to (0.2bar with a strain gauge pressure transducer (Sensotec),and the temperature was controlled to within (0.1°C.Surfactant was initially loaded into the view cell,and the desired amount of CO 2was added with the pressure generator.The pressure was increased,and the system equilibrated at the desired T ,for ∼2h,by using a magnetic stir bar.The cloud point of the surfactant was obtained as described above.The solution was then recirculated,and deionized water was injected into the system via the 150-µL sample loop in the switching valve.The solution was sheared through a 130µm i.d.×50mm long stainless steel capillary tube upstream of the optical cell.Emulsion formation and stability were characterized based upon turbidity measurements versus time (t )at a constant wavelength (λ)650nm)and also visual observation.The turbidity is a measure of the reduction in transmitted intensity,τ)(1/l )ln(I 0/I ),where l is the path length and I 0and I are the incident and transmitted intensities,respectively.After the injection of each increment of water,the emulsion was stirred and recirculated for ∼20min (approximate time required for the absorbance to reach a maximum value).Immediately after recirculation and stirring were stopped,τmeasurements started.The stability was assessed from τas a function of t ,while the(34)Jacobson,G.B.;Lee,C.T.;daRocha,S.R.P.;Johnston,.Chem.,in press.(35)Jacobson,G.B.;Lee,C.T.;Johnston,.Chem.,in press.(36)Adamsky,F.A.;Beckman,E.J.Macromolecules 1994,27,312-314.(37)Chittofrati,A.;Lenti,D.;Sanguineti,A.;Visca,M.;Gambi,C.M.C.;Senatra,D.;Zhou,Z.Prog.Colloid Polym.Sci.1989,79,218-(39)Jennings,J.W.;Pallas,ngmuir 1988,4,959-967.Figure 2.Apparatus for emulsion formation and turbidimetry measurement.∆P )2γ/R 0+(∆F )gz(1)Surfactant Effect on Interfacial Tension Langmuir,Vol.15,No.2,1999421effective average droplet size was determined fromτversusλ.For a monodisperse system of nonabsorbing spheres in theabsence of multiple scatteringτis given byτ)3K*φ/2D,42where φis the dispersed phase volume fraction,D is the droplet diameter, and K*is the scattering coefficient.According to Mie theory,Κ*is a complex function of R(R∼D/λ,whereλis the wavelengthof the incident light)and m the ratio of the refractive indices ofthe dispersed and continuous phases.The refractive indices wereapproximated by those of the pure components,water(1.333)and CO2.43By evaluation of turbidities at two wavelengths,theaverage droplet size can be determined by an iteration proce-dure.44Results and DiscussionInterfacial Tension of the CO2-Water Binary System.The interfacial tension between pure CO2and water is shown in Figure3for two temperatures as a function of pressure,along with the data of Heurer18and Chun and Wilkinson.19Our interfacial tensions were measured1h after drop formation.Theγvalues obtained by Chun and Wilkinson19were measured with the capillary rise technique.Whereas local equilibrium was achieved within the capillary tube,the entire system was not at equilibrium.Heurer used the pendant drop technique; however,the values reported were obtained from the drop profile within10s of drop formation.Therefore,the lower values ofγin the present study suggest a closer approach to true equilibrium.A simple physical picture may be used to explain the behavior for most of the pressure range studied.16At pressures below70bar,γdecreases with increasing pressure.The cohesive energy density or free energy density of CO2is well below that of water at all pressures. The density and free energy density of CO2change over a wide range with pressure,whereas the values for essentially incompressible water are constant.As the density of the CO2phase increases,its free energy density becomes closer to that of water,andγdecreases.At low pressures where the density and free energy density change a great deal with pressure,the decrease inγis pronounced.At high pressures,where CO2is more “liquidlike”,it is much less compressible and the decrease inγwith pressure is small.For the CO2-PEG600interface,γwas predicted quantitatively with a gradientmodel and the lattice fluid equation of state.16The latticefluid model is less applicable for water due to thecomplexities resulting from hydrogen bonding and car-bonic acid formation.A cusp in the curve ofγversus pressure is observed attemperatures and pressures near the critical point of CO2.The region of the cusp inγshifts to slightly higherpressures as the temperature is increased above the criticaltemperature of CO2.For supercritical temperatures,themagnitude of the cusp increases as the temperature isdecreased toward the critical temperature.At25,1935,and38°C,the cusp in the interfacial tension is verynoticeable,while it becomes small at45°C and is notvisible at71°C.18The following argument explains how the cusp is relatedto the large compressibility of CO2.An upward pointingcusp has been observed for the surface excess of ethyleneon graphitized carbon black.45The excess adsorption canbe defined in terms of the density of the bulk phase andthe density of the interfacial region46where F(z)is the molar density of the fluid at a distancez from the surface.At pressures below the critical pressureregion,F(z)can be much larger than F,due to attractionof solvent to the surface,leading to a largeΓex.At higherpressures,the bulk fluid is much denser,so that thedifference between F(z)and F is much smaller resultingin a smallerΓex.As temperature increases above thecritical temperature of the solvent,the tendency of thesurface to raise F(z)to“liquidlike”densities diminishesandΓex decreases.Similar arguments apply to theadsorption of CO2at the water-CO2interface.TheenhancedΓex is manifested as the downward cusp inγ.Inboth examples,the cusps become broader and shift tohigher pressures at higher temperatures.Similar behavioris observed for peaks in plots of the isothermal compress-ibility of pure CO2versus pressure at constant temper-ature.To put the above results in perspective,new interfacialtension data are shown for the PEG600-CO2interface tocomplement earlier data16only at45°C(Figure4).Thevalues ofγfor the water-CO2interface are considerablylarger than those for the PEG600-CO2,PS(M n)1850),23CO2-PEHA(M n)32k)interfaces.22This result is dueprimarily to the much larger surface tension of water,∼72mN/m,versus that of PEG,∼35mN/m,and PEHA, 30mN/m.However,it is interesting thatγbetween CO2and water at high pressures,20mN/m,is below that forwater-hydrocarbon interfaces.For heptane and octane,the hydrocarbon-waterγis about50mN/m.This lower γis consistent with the higher miscibility between CO2 and water47versus hydrocarbons and water.The stronger interactions between CO2and water versus hydrocarbons and water are due to the small size of CO2which causes a smaller penalty in hydrophobic hydration,CO2’s quad-rupole moment,and,finally,Lewis and Bronsted acid-base interactions.Over the entire pressure range for PEG600-CO2at25and45°C,the interfacial tension decreased monotonicallywith increasing pressure,unlike the case for CO2-water(42)Yang,K.C.;Hogg,R.Anal.Chem.1979,51,758-763.(43)Burns,R.C.;Graham,C.;Weller,A.R.M.Mol.Phys.1986,59,(45)Findenegg,G.H.In Fundamentals of Adsorption;Myers,A.L., Belfort,G.,Eds.;Engineering Foundation:New York,1983;p207.Figure3.Interfacial tension at the CO2-water interface asa function of pressure at various temperatures.Γex≡∫(F(z)-F bulk)d z(2) 422Langmuir,Vol.15,No.2,1999da Rocha et al.at 35°C.The lack of a dip near the critical pressure may be due to the much lower compressibility at 25and 45°C versus 35°C.This contrast in behavior may also be due to a difference in the density gradient and thickness in the interfacial region for the two systems,for example,greater miscibility for the CO 2-PEG600system.Interfacial Tension:PFPE Ammonium Carboxy-late.The addition of small amounts of PFPE COO -NH 4+decreases γsubstantially as shown at 45°C and 276bar in Figure 5.As the concentration is raised above 0.03%surfactant,a discontinuity is observed,and the magnitude of the slope becomes much smaller.Because it has been shown that w/c microemulsions are formed in this system,14the discontinuity can be attributed to a critical microemulsion concentration (c µc)for the PFPE COO --NH 4+surfactant,as has been done for oil -water inter-faces.24At concentrations above the c µc,the less negative slope is caused by the addition of surfactant primarily to adsorption at the pendant drop interface,the change in γis reduced.The adsorption obtained from the Gibbs’adsorption equationfor the PFPE COO -NH 4+surfactant was 1.77×10-10mol/cm 2,which corresponds to a surface coverage of ∼100Å2/molecule.Such a high surface coverage is sufficient for the formation of microemulsions.A comparable value of ∼140Å2/molecule was measured by Eastoe et al.48at 500bar and 25°C for the hybrid hydrocarbon -fluorocarbon C 7F 15CH(OSO 3-Na +)C 7H 15surfactant in CO 2.This value was determined by assuming that all the surfactant is adsorbed at the interface of spherical droplets of 25Å2radius,as measured by SANS,with a polydispersity of ∼0.2.The substantial reduction in γand relatively high surfactant adsorption explain why it was possible to form a w/c microemulsion with PFPE COO -NH 4+.The same surfactant had an absorption of 400Å2/molecule at the CO 2-PEG interface.16Phase behavior studies indicated that PEG-in-CO 2microemulsions are also formed with this surfactant,but the nature of the core has not been characterized.16Interfacial Tension:Fluoroether Sulfate and Sorbitol Surfactant.The phase behavior of fluoroether sulfates and fluoroether sorbitols was measured by Singley et al.38for various molecular weights of single-,twin-,and triple-tailed surfactants.The surfactants were soluble in CO 2at 33°C and moderate pressure (<300bar).The sorbitol surfactants were found to be more soluble in CO 2than the sulfate ones,as expected due to the low solubilities of ions in CO 2,because of its low dielectric constant.The results showed that branching depresses the cloud point curve of a surfactant until the solubility becomes domi-nated by the overall molecular weight.These surfactants were used to form CO 2-in-water and middle-phase emul-sions with excess CO 2and water.38The interfacial tension was measured at the water -CO 2interface for the single-tailed M w 2500sulfate and the triple-tailed (7500g/mol total)sorbitol surfactants.Our measured cloud point for the 1.4%(w/w)CO 2sorbitol surfactant was 215.6bar at 45°C.For 0.56%sulfate surfactant,it was 139.8bar at 45°C.The sulfate surfactant did not lower the interfacial tension significantly over the pressure range of 180-283bar 45°C at a concentration of 0.56%.The interfacial tension was difficult to determine accurately,because bubbles and possibly surfactant precipitate appeared on the surface of the pendant drop within 15min of drop formation.The interfacial tension was estimated to be ∼15mN/m by using manual edge detection of the pendant drop.For the sorbitol surfactant,the interfacial tension decreased to ∼5.5mN/m at 276bar and 45°C with a concentration of 1.4%.Relative to other surfactants reported in this study,these surfactants were less successful in lowering the interfacial tension.Interfacial Tension:PPO -PEO -PPO,PEO -PPO -PEO,and PBO -PEO Surfactants.Block co-polymers containing CO 2-philic and hydrophilic (CO 2-phobic)functional groups may be designed to be active at the CO 2-water interface.In this section,the CO 2-philic blocks are poly(propylene oxide)and poly(butylene oxide),while the CO 2-phobic block is poly(ethylene oxide).TheFigure 4.Interfacial tension for the PEG600-CO 2interface at varioustemperatures.Figure 5.Interfacial tension for the water -CO 2-PFPE COO -NH 4+system at 45°C and 276bar.The dotted line is used to determine the surfactant adsorption via the Gibbs adsorption equation.A discontinuity is present at the critical micromemulsion concentration.Γ2)-1RT (d γd ln c 2)T ,P(3)Surfactant Effect on Interfacial Tension Langmuir,Vol.15,No.2,1999423。

CHAPTER 1 CHARACTERISTIC FEATURES OF SURFACTANTS PROBLEMSWrite the structure formula for a surfactant type in current use that fits the general description in each case:1 Suitable for use in warm alkaline aqueous solution, but decomposes in warm acidic Solution2 An edible nonionic surfactant3 Suitable, at neutral pH, for making most solid surfaces hydrophobic4 An anionic surfactant unsuitable for use in a detergent bar for washing hands5 A surfactant based entirely upon synthetic polymers6 A zwitterionic surfactant whose structure dose not change with change in pH7 A surfactant that has the same chemical elements in both its hydrophilic and hydrophobic groups8 An anionic surfactant unsuitable for use in hot alkaline solution.CHAPTER 2 ADSORPTION OF SURFACE-ACTIVE AGENTSAT INTERFACES : THE ELECTRICAL DOUBLE LAYERPROBLEMS1 A nonionic surface-active solute in aqueous solution at 30℃ gives the following γ－㏒C data ( C in moles dm -3)γ(mJm -2): 71.4 60.0 52.0 40.6 29.2 29.2 29.2 ㏒C : -6.217 -5.992 -5.688 -5.255 -4.822 -4.691 -4.552The solpe of the γ－㏒C plots is linear at γ＜60 mJm -2 , down to the c.m.c. (a) Calculate the surface excess concentration , Г, in moles cm -2 at γ＜60 mJm -2 (b) Calculate the minimum surface area/molecule , in Å2(c) Calculate 0ad G , in KJ mol -12 Without looking at the tables , place the following compounds in order of increasing efficiency of adsorpotion ( increasing pC 20 value at the aqueous solution/air interface) :(a) 321024()CH CH CH SO Na -+(b) CH 3(CH 2)9SO(c) 328233()()CH CH CH N CH Cl +-(d) CH 3(CH 2)4CHCH 2SOC 3H 7(e) 32102246()()CH CH CH OC H OH3 Without looking at the tables , place the following compounds in order ofincreasing effectiveness of adsorption (increasing Гm ) at the aqueous solution/air interface . Use ≈if two or more compounds have approximately equal Гm values :(a) 10214C H SO Na -+ (in H 2O)(b) 12254C H SO Na -+ (in H 2O)(c) 16334C H SO Na -+(in H 2O)(d) 16334C H SO Na -+(in 0.1M NaCl)(e) 18374C H SO Na -+(in H 2O)4 If 1/k ≈10Å for 0.1 M NaCl in aqueous solution at room temperature , calculate 1/k for 0.1 M CaCl 2 under the same conditions5 2.0 g of a solid , whose specifics surface area is 50 m 2/g , is shaken with 100 mL of a 1×10-2 M solution of a surfactant . After equilibrium is reached , the concentration of the surfactant solution is 7.22×10-3 M . Calculate the average area occupied per surfactant molecule on the solid surface , in Å26 The molar concentration of two individual surfactants required to yield a surface tension value of 36 dynes/cm in aqueous solution are 2.6×10-3 and1.15×10-3 , respectively . The total molar surfactant concentration to yield a surface tension of 36 dynes/cm is 6.2×10-4 for a mixture of the two surfactants in which the mole fraction of the first surfactant ( on a surfactant-only basis ) is 0.41 . Calculate the value of X 1 , the mole fraction of surfactant 1 in the total surfactant at the aqueous solution/air interface for this mixture.7 Indicate, in the table below the effect of each of the following changes on the surface tension reduction effectiveness Пcmc of the surfactant in aqueous solution . Use symbols: + = increase; - =decrease; 0 = little or no effect; ? = effect not clearly known.Change Effect(a) Increase in the length of the hudrophobic group(b) Replacement of straight chain hydrophobic groupby isomeric branched chain(c) For ionics , increase in the electrolyte content of theaqueous solution(d) Increase in the temperature of the solution8 Predict the effect of each of the following changes on the value of the Winsor ratio , R:(a) Increase in the length of the hydrophobic group of the surfactant(b) Increase in the length of the POE chain of a nonionic surfactant(c) Replacement of n-hexane by n-octane as the hydrocarbon phase(d) Addition of n-pentanol to the system(e) Addition of NaCl to the systemCHAPTER 3 MICELLE FORMATION BY SURFACTANTSPROBLEMS1 If we assume that the length of the alkyl chain of a surfactant in a micelle is 80% of its fully extended length , what would be the shape of the micelle of a surfactant whose hydrophobic group is a straight 12-carbon chain and whose hydrophilic group has cross-sectional area at the micellar surface of 60Å2 ?2 Indicate in the table below the effect of each change on the aggregation number of a micelle . Use symbols : + = increase ; - =decrease ; 0 = little or no effect ; ? = effect not clearly known.For compounds R(OC 2H 4)x OH in water( R = straight chain ): Effect a. Increase in temperatureb. Increase in the number of carbon atoms in Rc. Increase in the value of xFor compounds RS 4-Na + in water Effect b. Addition of electrolyte to the solutionc. Replacement of Na + by Li +d. Replacement of water as a solvent by methyl alcohol3 Place in order of increasing CMC in aqueous solution (list answers by letters) : (a) 32113()CH CH SO Na(b) 3211248()()CH CH OC H OH(c) 3293()CH CH SO Na(d) CH 3(CH 2)8CHSO 3Na2H 5(e) CH 3(CH 2)9SO 3Na(f) 3211244()()CH CH OC H OH4 Calculate the 0mic G , in kJmol -1 , for a nonionic surfactant whose CMC is 4×10-4mol/liter at 27℃5 Indicate in the table below the effect of each change on the CMC/C 20 ratio of the surfactant in aqueous solution. Use symbols : + = increase ; - =decrease ; 0 = little or no effect ; ? = effect not clearly known.Change Effecta. Increase in the length of the hydrophobic groupb. Branched , instead of straight chain , isomerichydrophobic groupc Addition of urea to aqueous solutiond Addition of NaCl to aqueous solution of ionic surfactante Decrease in the length of the polyoxyethylene chain(nonionic surfactant)6 Derive the following relationships for mixed micelle foration in a mixture of the two surfactants in aqueous solution . Define all symbols . (a) 111,01M MM M C f X C = (b) ,0,01212,0,01121(1)M M M M M C C C C C αα=-+, for ideal mixed micelle formation7 Without using the tables , place the following compounds in order of decreasing CMC/C 20ratios . Use if values are approximately equal(a) 12254C H SO Na -+ , in H 2O , 25℃(b) 12254C H SO Na -+, in H 2O , 40℃(c) 12254C H SO Na -+ , in 0.1M NaCl (aq.) , 25℃(d) 122533()C H N CH Br +- in H 2O , 25℃(e) 1225246()C H OC H OH in H 2O , 25℃CHAPTER 4 SOLUBILIZATION BY SOLUTIONSOF SURFACTANTS: MICELLAR CATALYSISPROBLEMS2Predict the locations of the following solubilizates in a micelle of C12H25SO4Na in aqueous medium(a)Toluene(b)Cyclohexane(c)n-Hexyl alcohol(d)n-Dodecyl alcohol3Predict the effect of the following changes on the solubilization capacity of a micelle of R(OC2H4)x OH in aqueous medium for the two solubilizates given below . Use the symbols: + = increase; - =decrease; 0 = little or no effect; ? = effect not clearly predictableChange Effect forn-Octane n-Octylamine(a) Increase in the value of x(b) Increase in the temperature to thecloud point(c) Addition of electrolyte(d) Addition of HCl(e) Increase in the chain length, R3Predict the effect on the solubilization of water , by micelles of R(OC2H4)x OH in heptane of :(a). Increase in the value of x(b). Increase in the temperature(c). Addition of electrolyte(d) Addition of HCl(e) Increase in the chain length, R4Explain why it is advisable to use a solution ofC H CO CH SO at a1123223 concentration above its CMC in distilled water soon after it is prepared , if one wishes to obtain an accurate measurement of its surface tension . (The pH of distilled water is about 5.8)CHAPTER 5 WETTING AND ITS MODIFICATION BY SURFACTANTS PROBLEMS1(a) The Good-Girifalco factor Ф , which is a measure of the degree of interaction between the two phases in contant at an interface , varies from0.5 when interaction is minimal to about 1.1 when interaction is strong . What can you conclude regarding the strength of the interaction of water (LA γ = 72dynes/cm at 25℃) and a liquid , X , whose surface tension is 20dynes/cm at 25℃ , if the interfacial tension between them at that temperature is 45 dynes/cm ?(b) What is the value of the spreading coefficient in this system ?2 For low energy surfaces , C γ, the critical surface tension for wetting , is oftenequated with SA γ . What is the implication of this ?3 Water at 25℃(LA γ= 72dynes/cm) makes a contact angle of 102° on a solidsubstrate . The addition of a surfactant to the water decreases the surface tension to 40dynes/cm and the contact angle to 30°. Calculate the change in the work of adhesion of the water to the substrate as a result of the surfactant addition .4 Suggest a reason for the observation that POE nonionics often show shorterwetting times than anionics on hydrophobic substrates but show longer wetting times than anionics on cellulosic substrates.CHAPTER 6 EMULSIFICATIONPROBLEMS1 List 4 different ways of distinguishing O/W from W/O macroemulsions.2 Describe, or give the characteristic properties , of each of the following : (a) macroemulsion(b) miniemulsion(c) microemulsion(d) multiple emulsion3 Discuss the changes in interfacial tension that occur in the conversion of an O/W macroemulsion stabilized by a polyoxyethy-lenated nonionic surfactant to a W/O macroemulsion , upon raising the temperature above the cloud point.4 Explain the relationship between OE γ , WE γ , spreading coefficient , and emulsion type .5 An oil has an HLB of 10 for O/W emulsification . Calculate the percentages of1225242()C H OC H OH and 1225248()C H OC H OH that should be used inattempting to emulsify this oil with a mixture of these two surfactants.CHAPTER 7 FOAMING AND ANTIFOAMINGBY AQUEOUS SOLUTIONS OF SURFACTANTSPROBLEMS1 Explain why film elasticity is greatest in the region of the CMC2 Discuss two properties of surfactants that account for the existence of film elasticity.3 Describe two different mechanisms by means of which antifoams operate.4 Give structural formulas for 3 different types of low-foaming surfactants , indicating the structural characteristics that cause them to foam pooly.5 Calculate the time it would take for the surface concentration to reach a value of 2×10-10 moles per cm 2 from a 1×10-2 M solution of surfactant in the absence of stirring or an energy barrier to adsorption . Assume the bulk diffusion constant of the surfactant to be 2×106 cm 2/sec.CHAPTER 8 DISPERSION AND AGGREGATION OF SOLID IN LIQUIDMEDIA BY SURFACTANTSPROBLEMS1 List three different ways of increasing the stability of a dispersion of an ionic solid in liquid .2 Discuss two different mechanisms by which the polyoxyethylene chain in a nonionic surfactant adsorbed on a finely divided hydrophobic substance can help stabilize a dispersion of that substance in water3 Explain why Ca ++ is much more effective than Na + , at the same molar concentration in the solution phase , as a flocculant for an aqueous dispersion stabilized by an anionic surfactant .4 Which one of the following , at the same molar concentration in the solution phase , would be expected to be the most effective stabilizer for a dispersion of a positively changed hydrophilic solid in heptane ?(a) 1225242()C H OC H OH(b) 1225248()C H OC H OH(c) 122533()C H N CH Cl +-(d) Sodium ligninsulfonate5 A dispersion of an ionic solid in aqueous medium is precipitated by small amountsof 12254C H SO Na -+ or 12252410()C H OC H OH , but is unaffected by the additionof 122533()C H N CH Cl +- . What conclusions regarding the mixture of the solid can be drawn from these data?6 Discuss the effect of the following surfactants on an aqueous dispersion of a water-insoluble salt of a polyvalent metal whose particles are positively-charged:(a) A small amount of 12254C H SO Na -+(b) A small amount of 12252410()C H OC H OH(c) A small amount of 122533()C H N CH Cl +-(d) A large amount of 1225643C H C H SO Na -+CHAPTER 9 DETERGENCY AND ITS MODIFICATIONBY SURFACTANTSPROBLEMS1 Explain why cationic surfactants , which ordinarily show poor detergency inaqueous media , can be used successfully as detergents at low pH2 Explain how the addition of a small amount of a cationic surfactant can increasethe efficiency of an alkaline solution of an anionic surfactant in soil removal from a textile surface .3 (a) What effect would adsorption of a surfactant onto a textile surface via itshydrophilic head have on the spreading coefficient of the bath on the textiles surface ?(b) List two cases where this may occur .CHAPTER 10 MOLECULAR INTERACTIONS AND SYNERGISM INMIXTURES OF TWO SURFACTANTSPROBLEM S1 (a) Surfactant A has a pC 20 value of 3.00 in 0.1 M NaCl (aq); surfactant B has apC 20 value of 3.60 in the same medium . The σβ value for the mixture in0.1M NaCl is – 2.80 . Will a mixture of surfactants A and B in 0.1M NaCl show synergism in surface tension reduction efficiency ?(b) If this system does show synergism of this type , calculate the value of α* (the mole fraction of surfactant A in the mixture , on a surfactant-only basis ,at the point of maximum synergism) and C 12,min (the minimum total molar surfactant concentration to yield a 20dyne/cm reduction in the surface tension of the solven) .2 Surfactants C and D have CMC values of 1.38×10-4 an 4.27×10-4 moles/liter ,respectively , in aqueous 0.1M NaCl . This mixture , in the same medium , has a CMC value of 3.63×10-4 moles/liter , when the mole fraction αof surfactant C in the mixture is 0.181 ( on a surfactant-only basis)(a) Calculate M β for a mixture of surfactants A and B(b) Will this mixed system exhibit synergism or negative synergism in mixedmicelle formation ? If so , calculate the values of *α and 12.min M C3 Surfactants C and D of problem 2 individually reduce the surface tension of anaqueous 0.1M NaCl solution to 30dynes/cm when their respective molar concentrations are 9.1×10-5 and 3.98×10-4 . The mixture of them at α=0.181 in problem 2 has a surface tension value of 30dynes/cm when the total molar surfactant concentration is 3.47×10-4 .Will a mixture of surfactants C and D exhibit synergism or negative synergism in surface tension reduction effectiveness ?4 Without consulting tables , place the following mixtures in order of increasingattractive interaction ( increasing negative σβ value ) at the aqueous solution/air interface :(a) 122524612253()C H OC H OH C H SO Na -+-(H 2O)(b) 122524612252415()()C H OC H OH C H OC H OH -(0.1M NaCl , H 2O)(c) 1225312253222()()C H SO Na C H N CH CH COO H O -++--(d) 12253312253222()()()C H N CH Cl C H N CH CH COO H O +-+--。

中国吏州眼科杂志第ｌｇ卷（：００１）辩７娟硅油填充眼的白内障超声乳化联合硅油取出术福建泉州市ＪＬ童医院北京同Ｌ跟科中心３６２。

ｏＯ北京问Ｌ医院眼科谢江斌魏文斌／狮Ａ目的：探讨玻璃体视网膜手术联台硅油眼内填充术后并发性白内障行白内障超声乳化和７或人工晶体植人联合辞油取出术的临床教粜。

方法：对２２例２２跟硅油填克术后＂发性亡Ｊ内障进行白内障超声乳化联合硅油取出手术．其中９例通过巩膜隧道切口植人硬性八工晶体，３例通过角膜切口植＾折叠人丁晶体．】０例未植八人上晶体．结果：２２例ｆ术１－后囊膜保持完整．除１０例因高度近视、视网膜条件很差或再发视网膜脱离而未植人人工晶体外．其余均顺利植＾人上晶体。

术后ｊ例发牛角膜水肿，均在术后３～７天内消退。

硅油取出顺利。

３例术中发现限局性网脱．行视网膜复位后．！侧ｃ２Ｆ６气体填亢术后２周再发｜ｃ４脱．】侧再次硅油填充视网膜保持复忙．视力除３倒再发网脱外．其余均达到玻璃侔手术后最佳视力结论：硅油填充眼台片白内障行白内障超声乳化联合硅油取出手术不仅安全、有效、而且可减少病人多次手术的痛苦。

关键词：硅油白内障超声乳化Ｐｈａｃｏｅｍｕｌｓｉｆｉｆａｔｉｏｎ∞ｍｂｌｎｅｄｓｌｌｌｃｏｎｅｏｉｌｒｃｍｏｖｅｉｎｔｋ。

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2004年第62卷第16期,1491～1494化学学报ACT A CHIMICA SINICAV ol.62,2004N o.16,1491～1494高浓度无机盐对正负离子等摩尔混合表面活性剂表面活性的影响张　莹 陈　莉 肖进新Ξ 马季铭Ξ(北京大学化学与分子工程学院　北京100871)摘要　一般认为无机盐对等链长正负离子表面活性剂等摩尔混合体系的表面活性没有明显影响.通过测定等摩尔癸基三乙基溴化铵和癸烷磺酸钠混合体系在卤化钠(NaX,X=F-,Cl-,Br-,I-)溶液中的表面活性,发现高浓度的无机盐具有明显影响,使混合表面活性剂的临界胶束浓度(cmc)降低,水溶液的最低表面张力(γcmc)升高.无机盐的影响程度随NaX中X的离子半径增加而增大.可通过无机反离子对正负离子表面活性剂头基之间吸引作用的“屏蔽”及“盐析”作用对结果加以解释.关键词　表面活性剂,正负离子表面活性剂混合体系,表面张力,表面活性E ffect of Salt with H igh Concentration on Surface Activities of EquimolarMixtures of C ationic2Anionic SurfactantsZH ANG,Y ing CHE N,Li XI AO,Jin2X inΞ M A,Ji2Ming(College o f Chemistry and Molecular Engineering,Peking Univer sity,Beijing100871)Abstract　It is usually thought that inorganic salts have little effect on the surface activity of equim olarly mixed cationic2anionic surfactant mixtures.This w ork studied the effect of s odium halide(NaX,X=F-,Cl-,Br-,I-) on the surface activity of equim olarly mixed decyltriethylamm onium bromide2s odium decanesu fonate.It was showed that the added salts with high concentration had obvious effect on the surface activities,and the critical micelle concentration(cmc)was decreased,while the lowest surface tension of the aqueous s olution(γcmc)was increased. Such effects were increased with ion radius of X-of NaX.The results were explained in terms of the“screening”effect of inorganic counter ions on the attraction between oppositely charged headgroups of mixed cationic2anionic surfactants and the“salt out”effect.K eyw ords　surfactant,cationic2anionic surfactant mixture,surface tension,surface activity 正负离子表面活性剂混合体系具有单一表面活性剂无法比拟的高表面活性[1].这是由于反电性极性基之间强烈的静电吸引作用,使得表面活性剂分子更易于在表面吸附(表面吸附层中疏水链密度增大)及在溶液内部自聚.一般认为,对于等碳链长的正、负离子表面活性剂等摩尔混合体系,无机盐的加入对其表面活性没有显著影响,因为在等摩尔混合溶液的界面上和胶团中,正、负表面活性剂离子电性自行中和,扩散双电层不复存在[2,3].大量实验也表明加盐与不加盐体系的表面张力-浓度对数曲线基本重合[3].应该指出的是,上述研究及结论都是在较低盐浓度(一般为0105～011m ol・L-1)下得到的.由于大多数等摩尔混合的正负离子表面活性剂体系在很低浓度即形成沉淀,无机盐的加入会使混合表面活性剂的溶解度更加降低,因而使得人们难以研究高浓度无机盐对其表面活性的影响.最近我们发现癸基三乙基溴化铵[C10H21N(C2H5)3Br,C10NE]和癸烷磺酸钠(C10H21SO3Na,C10SO3)等摩尔混合体系在很高浓度也可形成均相溶液[4],这使我们有了合适的体系研究高浓度无机盐的影响.本工作通过表面张力测定研究了卤化钠(NaX,X= F-,Cl-,Br-,I-)在较高浓度范围内对C10NE2C10SO3等摩尔混合均相体系表面活性的影响.ΞE2mail:xiaojx@;T el:010*********.Received December11,2003;revised M arch6,2004;accepted April20,2004.国家自然科学基金(N os.29973002,20273006)资助项目.1　实验部分1.1　原料癸基三乙基溴化铵[C 10H 21N (C 2H 5)3Br ,简写为C 10NE],用溴代癸烷和三乙胺反应制备,产物用丙酮-乙醚混合溶剂重结晶五次.癸基磺酸钠(C 10H 21SO 3Na ,简写为C 10SO 3),分析纯,日本东京化成工业株式会社.这两种表面活性剂的表面张力曲线均无最低点,表明没有高表面活性的杂质存在.NaF ,NaCl ,NaBr 和NaI ,分析纯,北京化工厂.水为二次重蒸水.1.2　溶液表面张力的测定和cmc ,γcmc 的确定溶液表面张力用滴体积法测定[5].实验温度为(25±011)℃.实验误差范围为±012mN ・m -1.根据测出的各体系的表面张力γ与表面活性剂浓度c 的关系,以γ对lg c 作图(γ2lg c 曲线),转折点处相应浓度为临界胶束浓度(cmc ),相应的γ为γcmc .2　结果和讨论图1为不同阴离子NaX 存在下,C 10NE 2C 10SO 3等摩尔混合体系的γ2lg c T 曲线(c T 为正负离子混合表面活性剂的总浓度).因为当[NaF]>0154m ol ・L -1时,混合溶液将发生相分离,生成双水相体系[6],因而图1中,[NaF]=0150m ol ・L -1,其它三种盐浓度均为110m ol ・L -1.图1　C 10NE 2C 10S O 3等摩尔混合体系的γ2lg c T 曲线(25℃)Figure 1　γ2lg c T plot of equim olarly mixed C 10NE 2C 10S O 3(25℃)图1表明,当外加无机盐NaX 的阴离子为F -,Cl -和Br -时,溶液的γ2lg c T 曲线与无外加盐的C 10NE 2C 10SO 3等摩尔混合体系γ2lg c T 曲线比较接近;而当NaX 的阴离子为I -时,溶液γ2lg c T 曲线与不加盐时相比偏离得十分明显.于是我们考虑减小外加NaI 的浓度,看这种偏离是否仍然存在.图2为溶液中[NaI]=015m ol ・L -1和[NaI]=110m ol ・L -1时,γ2lg c T 曲线的对比.从中可以看出,当[NaI]=015m ol ・L -1时,其对C 10NE 2C 10SO 3等摩尔混合体系γ2lg c T 曲线的影响已很明显.图2　C 10NE 2C 10S O 3等摩尔混合体系的γ2lg c T 曲线(25℃)Figure 2　γ2lg c T plot of equim olarly mixed C 10NE 2C 10S O 3(25℃)表面活性剂的表面活性通常用cmc 和γcmc 来表征,而表面活性剂分子在气液界面吸附层的排列情况,可以通过比较饱和吸附时表面活性剂分子平均占有面积和分子自身尺寸来推测.首先可应用G ibbs 吸附公式[1]:Γ=-12×2.303RT 9γ9lg cT(式中Γ为表面活性剂浓度为c 时的表面吸附量)和γ2lg c曲线中直线段斜率可计算出极限(饱和)吸附量Γm ,然后由下式计算表面活性剂分子在表面层的极限吸附分子面积A m :A m =1N 0Γm式中N 0为Av ogadro 常数.图1～2数据处理的结果列于表1中.由表1可以看出,当外加NaX 的阴离子按F -,Cl -,Br -,I -变化时,C 10NE 2C 10SO 3等摩尔混合体系的γcmc 呈现增大趋势.加入NaF ,NaCl 和NaBr 时,这种增大不很明显;但NaI 对体系γcmc 的影响则十分明显.为进一步讨论NaI 对γcmc 的影响,我们测定了c T =3010mm ol ・L -1时,混合溶液表面张力随NaI 浓度的变化,结果示于图3.图3表明γcmc 随NaI 浓度的升高而增大,当[NaI]=210m ol ・L -1时,可使混合体系的γcmc 值增大约4mN ・m -1.已知无机盐可使水的表面张力升高.为证明上述表面张力的升高是否由无机盐对水的表面张力的影响所致,我们测定了上述NaX 水溶液的表面张力,结果示于图4.图4数据表明,无机盐虽然可使纯水的表面张力升高,但很有限.因此,可以认为上述表面张力的升高是由于无机盐对表面活性剂的影响所致.2941 化学学报V ol.62,2004表1　外加盐对C 10NE 2C 10S O 3等摩尔混合体系表面活性的影响(25℃)T able 1　E ffect of salts on the surface activity of equim olarly mixed C 10NE 2C 10S O 3(25℃)Saltc salt /(m ol ・L -1)γcmc /(mN ・m -1)cmc/(mm ol ・L -1)Γm /(10-10m ol ・cm -2)A m /nm2N o salt 26.9 3.4 4.20.39NaF 0.526.9 2.0 4.20.39NaCl 1.027.4 2.3 4.20.39NaBr 1.028.0 2.3 4.20.39NaI 0.529.0 1.6 3.80.44NaI 1.030.6 1.5 3.60.46NaI2.030.9图3　NaI 对C 10NE 2C 10S O 3等摩尔混合体系表面张力的影响(25℃)Figure 3　E ffect of NaI on the surface tension of equim olarly mixed C 10NE 2C 10S O 3(25℃)图4　无机盐对纯水表面张力的影响(25℃,c 盐=1.0m ol ・L -1)Figure 4　E ffect of inorganic salts on the surface tension of water (25℃,c salt =1.0m ol ・L -1)对γcmc 的影响也反映在表面活性剂分子在表面吸附层的饱和吸附量Γm 及饱和吸附时分子平均占有面积A m 的变化上.由表1可以看出,NaI 的加入使Γm 明显减小,A m 明显增大.换言之,NaI 的加入使吸附层分子排列变得松散.由表1可以看出,C 10NE 2C 10SO 3等摩尔混合体系中加入高浓度的NaX 后,溶液的cmc 值普遍减小.不加盐时,溶液的cmc 值在313mm ol ・L -1左右;加入110m ol ・L -1的NaI 时,溶液的cmc 值降至115mm ol ・L -1.前文指出[4],在我们所试验的浓度范围内(c T 高达012m ol ・L -1),C 10NE 2C 10SO 3等摩尔混合体系均为均相溶液,其分子聚集体的平均流体力学半径在20nm 以下.一般认为加入无机盐将降低正负离子混合表面活性剂的水溶性.我们的研究表明,对于C 10NE 2C 10SO 3等摩尔混合体系,在本工作中所用的如此高的NaX 浓度(如2m ol ・L -1NaI ,其质量分数为30%),仍为均相溶液.对于离子型表面活性剂的单组分溶液,加入电解质后,通常会使溶液中的聚集体长大.对于正负离子表面活性剂混合体系,研究结果亦表明,加入电解质后聚集体会向更大的结构转变[7,8].然而我们的研究却发现,对于C 10NE 2C 10SO 3混合均相体系,外加盐(如NaBr 和NaI )的加入甚至会使混合体系的聚集体变小[9].如对总浓度30mm ol ・L -1的C 10NE 2C 10SO 3等摩尔混合体系,在2m ol ・L -1NaI 存在时,其聚集体的平均流体力学半径由无NaI 时的15nm 降低到215nm [9],这正是此混合体系在高浓度无机盐存在下仍为均相溶液的原因.无机盐对单一离子型表面活性剂的影响主要表现在无机盐反离子压缩了表面活性剂离子头的离子氛厚度,减少了表面活性剂离子头之间的排斥作用,从而使表面活性剂更容易在表面吸附,也更容易形成胶团,导致溶液的表面张力与cmc 降低[1].而对于等碳链长的正、负离子表面活性剂等摩尔混合体系,由于反电性极性基之间强烈的静电吸引作用,在溶液的界面上和胶团中,正、负表面活性剂离子电性自行中和,扩散双电层不复存在[1,3].因而无机盐的加入对其表面活性没有明显影响.正负离子表面活性剂混合体系突出的高表面活性也正是源于此种反电性极性基之间强烈的静电吸引作用.我们认为,当无机盐的浓度较高时,正、负离子表面活性剂反电性极性基之间的静电吸引作用会被削弱.其机理类似于无机反离子对单一离子型表面活性剂的影响.所不同的是,对单一离子型表面活性剂,无机反离子减弱了表面活性剂离子头之间的排斥作用;而对于正负离子混合表面活性剂,无机阳离子和阴离子则分别通过压缩阴离子和阳离子表面活性剂离子头的离子氛厚度,减弱了正、负离子表面活性剂离子头之间的吸引作用,从而使混合表面活性剂吸附量下3941N o.16张　莹等:高浓度无机盐对正负离子等摩尔混合表面活性剂表面活性的影响降,并且使吸附层分子排列变得松散,导致溶液的表面张力升高.也正是由于此种作用,表面活性剂分子在聚集体中排列变得松散,导致聚集体变小.研究表明,电解质离子的半径越小,其水合半径就越大[10],其对离子型表面活性剂极性基的电性屏蔽作用就越小.因而,随NaX 中X 离子半径的增加,其对正负离子表面活性剂混合体系γcmc 的影响逐渐增大,以NaI 的影响最为明显.如果按上述解释,半径较大的阴离子会削弱相反电性表面活性剂分子头基之间的吸引,那么高浓度外加盐应该不利于表面活性剂胶团形成,即增大体系的cmc.然而结果却与此相反.这可能因为高浓度外加盐对表面活性剂分子还存在“盐析”作用.“盐析”作用使表面活性剂分子更容易自聚形成胶团[3],导致cmc 降低.3　结论对于等链长正负离子表面活性剂等摩尔混合体系,当无机盐浓度较小时,对其表面活性影响很小.但高浓度无机盐则有明显影响.一方面可削弱正、负离子表面活性剂离子头基之间的吸引作用,使表面张力升高;另一方面则由于其“盐析”作用使cmc 降低.R eferences1X iao ,J.2X.;Zhao ,Z.2G.In Application Principle o f Sur factants ,Chemical Industry Press ,Beijing ,2003,p.433,p.54(inChinese ).(肖进新,赵振国,表面活性剂应用原理,化学工业出版社,北京,2003,p.433,p.54.)2Zhao ,G.2X.;X iao ,J.2X.Acta Phys.2Chim.Sin.1995,11(9),785(in Chinese ).(赵国玺,肖进新,物理化学学报,1995,11(9),785.)3Zhao ,G.2X.;Zhu ,B.2Y.In Action Principle o f Sur factants ,Chinese Light Industry Press ,Beijing ,2003,p.356(in Chinese ).(赵国玺,朱　瑶,表面活性剂作用原理,中国轻工业出版社,北京,2003,p.356.)4Chen ,L.;X iao ,J.2X.;Ruan ,K.;Ma ,ngmuir 2002,18,7250.5Zhu , B.2Y.;Zhao ,G.2X.Chemistry 1981,6,341(inChinese ).(朱　瑶,赵国玺,化学通报,1981,6,341.)6Chen ,L.;X iao ,J.2X.;Ma ,J.2M.Acta Phys.2Chim.Sin.2003,19(7),577(in Chinese ).(陈莉,肖进新,马季铭,物理化学学报,2003,19(7),577.)7Brasher ,L.L.;Herrington ,K.L.;K aler , ngmuir 1995,11,4267.8Bergstrom,M.;Pedersen ,J.S.J.Phys.Chem.B 1999,103,8502.9Chen ,L.Ph.D.Dissertation ,Peking University ,Beijing ,2003.(陈莉,博士论文,北京大学,北京,2003.)10Aswal ,V.K.;G oyal ,P.S.Phys.Rev.E 2000,61,2947.(A0312114　LU ,Y.J.;ZHE NG,G. C.)4941 化学学报V ol.62,2004。

适用于火腿肠、午餐肉等肉糜类制品，具有高强度、易分散、乳化效果好、持水性好、肉制品切片成形性好的特点。

◆参考配方◆参考工艺↓分享举报复配胶加入量对猪耳西式火腿物性的影响研究叶劲松，李洪军( 1 ．四川农业大学食品科学系，四川雅安；2 ．西南农业大学食品科学院，重庆)摘要：以猪耳为原料加工西式火腿，探讨了猪耳西式火腿的加工过程中复配胶加入量对产品物性的影响。

旨在为火腿制品的开发提供一定的实验依据；为猪耳的利用拓展一条新的途径。

结果表明，复配胶( 明胶一海藻酸钠复合剂)的加入对猪耳火腿的物性指标有明显影响，明胶一海藻酸钠配比以8 ：1计，总添加量为1 6 ．5 ％时，可使产品获得较理想的感官性能。

关键词：猪耳，西式火腿，复配胶，物性Abstract：The paper studies the physicochemical and sensory properties of the pig ears sandwichham.with the purpose of providing some experimentaI basis for the development of the sandwich ham and developing a new way for the use of pig ears.Theresults indicated show: when glutin,sodium alginate was 8:1,and dosage was 16.5 ％.satisfactory sensory properties could be obtainedKey words :pigs ears; sandwich ham; multi—pastern; physics property西式火腿是高营养、高水分、柔嫩多汁，具有良好的弹性、切片性的一种来源于西方的重要肉制品。

我国目前还没有规定火腿的分类标准。

The effect of surfactants on materialspropertiesSurfactants are compounds that play a crucial role in maintaining the stability and performance of materials in a wide range of industrial applications. These materials include polymers, paints, cosmetics, detergents, and even pharmaceuticals. Surfactants can affect the physical, chemical, and mechanical properties of materials. Their key role is to reduce the surface tension of liquids and solids, enable emulsifications and suspensions, and enhance wetting and spreading of the materials. In this article, we will explore the various ways in which surfactants affect materials properties.1. Surface TensionSurfactants can be characterized as amphiphilic molecules, meaning that they have both hydrophobic and hydrophilic regions. The hydrophobic part of the molecule prefers to stay away from water while the hydrophilic part is attracted to water. This property of surfactants disrupts the hydrogen bonding between water molecules and reduces the surface tension of liquids at the interface with air or other surfaces. This effect is critical in enhancing emulsification and wetting of materials.2. EmulsificationEmulsions are dispersed mixtures of two immiscible liquids such as oil and water. Surfactants can stabilize the emulsions by forming a layer around the dispersed droplets that prevents them from coalescing. The surfactant molecules adsorb at the oil-water interface, reducing the interfacial tension and promoting the formation of small droplets. The choice of surfactant depends on the nature of the materials and the desired stabilityof the emulsion.3. SuspensionSurfactants can also stabilize suspensions of solid particles in liquids. The surfactant molecules adsorb at the surface of the solid particles and form a protective layer thatprevents the particles from agglomerating. This effect is essential in the production of cosmetics, paints, and other products that require stable suspensions.4. WettingWetting is the ability of a liquid to spread on a surface. Surfactants can enhance wetting by reducing the contact angle between the liquid and the surface. This effect is due to the reduction in surface tension and adsorption of the surfactant molecules at the interface, which promotes spreading of the liquid. Surfactants are widely used in cleaning agents, personal care products, and agricultural formulations that require efficient dispersal and wetting.5. RheologySurfactants can affect the rheology of materials by altering their flow properties and viscosity. The surfactant molecules adsorb at the surface of the materials, creating a barrier that inhibits flow. This effect depends on the concentration and type of surfactant used and has significant implications for the processing and performance of materials.6. StabilitySurfactants play a critical role in stabilizing materials such as emulsions, suspensions, and foams. The surfactant molecules form a protective layer around the dispersed phase or bubbles, preventing them from coalescence or rupture. This effect is essential for the shelf life and performance of products such as food, cosmetics, and pharmaceuticals.ConclusionThe effect of surfactants on materials properties is multifaceted and complex. The properties of surfactants such as hydrophobicity, surface activity, and interfacial behavior have significant implications for the performance and stability of materials in various applications. The choice of surfactant, its concentration, and interaction with other components of the material are critical factors that determine the properties of the final product. Understanding the role of surfactants in materials science is essential for designing and processing materials with specific properties for various applications.。