Polyreactions in miniemulsions

聚苯并咪唑基质子交换膜的显微红外分析以“聚苯并咪唑基质子交换膜的显微红外分析”为标题，本文讨论了聚苯并咪唑基质子交换膜(PEMs)在显微红外频谱(MIR)分析中的应用。

近年来，MIR技术已成为分析材料表征的一种有效和广泛应用的方法。

它采用了漫反射传输仪和分子吸收红外光谱的技术来分析各种材料的表面结构和性质。

这种技术可以获得大量的信息，包括形状、尺寸、表面形状、表面化学和分子结构。

PEMs是分子形状控制和气体分离的有用材料，有着广泛的应用材料，如电池、燃料电池以及气体分离。

PEMs是一类结构相对复杂的有机交换膜，它们含有大量的有机物质，可以通过不同的水溶液、离子和基团等来控制表面性质及性能。

这使得MIR技术变得非常重要，可以用来识别PEMs的表面结构及性质的不同变化。

MIR技术已经在PEMs的分析中有了重要的应用。

MIR技术提供了快速准确的数据，可以用来特征鉴定、结构表征以及催化研究等。

MIR 技术可以用来快速识别PEMs表面上的有机物质，并准确测量膜层的厚度和介质的特性。

MIR技术分析不仅局限于分析PEMs表面的有机物质，还可以对其结构进行详细的表征和鉴定，以了解其影响表面性能的分子结构。

另外，MIR技术可以用来实时监控PEMs的动态表征，可以用来模拟离子交换的过程，并可以用来探索PEMs中的催化反应。

最后，MIR技术可以用来实时监测各种催化反应，以及用于研究吸附和分离性能。

综上所述，MIR技术对于研究PEMs的表面形状、组成、厚度和表面性质等是非常有用的。

此外，MIR技术也被用于实时监测和研究PEMs的动态行为，以及吸附、分离和催化性能。

未来，MIR技术将继续为PEMs的研究打下基础。

囊泡作为亲水性和亲脂性生物活性成分的药物传输载体已经得到广泛研究并已有实际应用。

囊泡通常由天然的、可生物降解的和无毒的分子制备，除了由磷脂制备的脂质体外，脂肪酸也能够形成囊泡[1-2]，且形成的囊泡是多分散的，尺寸可以从小囊构建乙氧基化磷脂稳定的油酸囊泡用作药物传输系统泡到巨囊泡。

脂肪酸比磷脂更廉价易得，因此，有作为磷脂替代品的可能，然而脂肪酸囊泡只能在很窄的pH 范围内形成，因此，其在长期储存过程中的不稳定性和对周围环境的热力学敏感性，阻碍了脂肪酸囊泡作为药物传输系统的适用性和有效性。

由王淑钰 薄纯玲1,2 王 杰1,2 王 轩1 茅沁怡1 方 云1（1. 江南大学化学与材料工程学院，2. 江南大学至善学院，江苏无锡，214000）摘 要：针对各类囊泡的优缺点，介绍了以油酸囊泡作为主体并辅以乙氧基化磷脂，使其形成非离子两亲物与油酸的复合囊泡作为纳米载体及其药物缓释性，并总结了脂肪酸囊泡的其他研究进展以及在日用化学品和洗涤用品领域的应用前景。

关键词：乙氧基化磷脂；油酸囊泡；脂肪酸囊泡；药物传输系统；纳米载体；洗涤用品中图分类号：TQ423 文献标识码：A 文章编号：1672-2701（2018）10-48-06__________基金项目：国家大学生创新训练计划资助项目（201710295005）。

作者简介：王淑钰，女，应用化学专业本科生；E-mail: wang_shuyu1@126,com。

通信联系人：方云，男，博士，教授，博导；E-mail: yunfang@。

非离子表面活性剂形成的非离子囊泡虽然稳定[3]，但囊泡粒径较难控制且原料昂贵[4]。

Teo [5]等人证实各种不饱和脂肪酸均能形成脂肪酸囊泡，最近Suk [6]等人发现：如果将脂肪酸囊泡的理念与非离子囊泡的理念相结合，仅需将少量非离子囊泡的囊材乙氧基化磷脂（DOPEPEG2000）加入到大量脂肪酸囊泡的囊材油酸（OA ）中就能形成稳定且粒径较大的囊泡，这在药品和日用化学品工业中具有应用价值。

Modeling of morphology evolution in the injection moldingprocess of thermoplastic polymersR.Pantani,I.Coccorullo,V.Speranza,G.Titomanlio* Department of Chemical and Food Engineering,University of Salerno,via Ponte don Melillo,I-84084Fisciano(Salerno),Italy Received13May2005;received in revised form30August2005;accepted12September2005AbstractA thorough analysis of the effect of operative conditions of injection molding process on the morphology distribution inside the obtained moldings is performed,with particular reference to semi-crystalline polymers.The paper is divided into two parts:in the first part,the state of the art on the subject is outlined and discussed;in the second part,an example of the characterization required for a satisfactorily understanding and description of the phenomena is presented,starting from material characterization,passing through the monitoring of the process cycle and arriving to a deep analysis of morphology distribution inside the moldings.In particular,fully characterized injection molding tests are presented using an isotactic polypropylene,previously carefully characterized as far as most of properties of interest.The effects of both injectionflow rate and mold temperature are analyzed.The resulting moldings morphology(in terms of distribution of crystallinity degree,molecular orientation and crystals structure and dimensions)are analyzed by adopting different experimental techniques(optical,electronic and atomic force microscopy,IR and WAXS analysis).Final morphological characteristics of the samples are compared with the predictions of a simulation code developed at University of Salerno for the simulation of the injection molding process.q2005Elsevier Ltd.All rights reserved.Keywords:Injection molding;Crystallization kinetics;Morphology;Modeling;Isotactic polypropyleneContents1.Introduction (1186)1.1.Morphology distribution in injection molded iPP parts:state of the art (1189)1.1.1.Modeling of the injection molding process (1190)1.1.2.Modeling of the crystallization kinetics (1190)1.1.3.Modeling of the morphology evolution (1191)1.1.4.Modeling of the effect of crystallinity on rheology (1192)1.1.5.Modeling of the molecular orientation (1193)1.1.6.Modeling of theflow-induced crystallization (1195)ments on the state of the art (1197)2.Material and characterization (1198)2.1.PVT description (1198)*Corresponding author.Tel.:C39089964152;fax:C39089964057.E-mail address:gtitomanlio@unisa.it(G.Titomanlio).2.2.Quiescent crystallization kinetics (1198)2.3.Viscosity (1199)2.4.Viscoelastic behavior (1200)3.Injection molding tests and analysis of the moldings (1200)3.1.Injection molding tests and sample preparation (1200)3.2.Microscopy (1202)3.2.1.Optical microscopy (1202)3.2.2.SEM and AFM analysis (1202)3.3.Distribution of crystallinity (1202)3.3.1.IR analysis (1202)3.3.2.X-ray analysis (1203)3.4.Distribution of molecular orientation (1203)4.Analysis of experimental results (1203)4.1.Injection molding tests (1203)4.2.Morphology distribution along thickness direction (1204)4.2.1.Optical microscopy (1204)4.2.2.SEM and AFM analysis (1204)4.3.Morphology distribution alongflow direction (1208)4.4.Distribution of crystallinity (1210)4.4.1.Distribution of crystallinity along thickness direction (1210)4.4.2.Crystallinity distribution alongflow direction (1212)4.5.Distribution of molecular orientation (1212)4.5.1.Orientation along thickness direction (1212)4.5.2.Orientation alongflow direction (1213)4.5.3.Direction of orientation (1214)5.Simulation (1214)5.1.Pressure curves (1215)5.2.Morphology distribution (1215)5.3.Molecular orientation (1216)5.3.1.Molecular orientation distribution along thickness direction (1216)5.3.2.Molecular orientation distribution alongflow direction (1216)5.3.3.Direction of orientation (1217)5.4.Crystallinity distribution (1217)6.Conclusions (1217)References (1219)1.IntroductionInjection molding is one of the most widely employed methods for manufacturing polymeric products.Three main steps are recognized in the molding:filling,packing/holding and cooling.During thefilling stage,a hot polymer melt rapidlyfills a cold mold reproducing a cavity of the desired product shape. During the packing/holding stage,the pressure is raised and extra material is forced into the mold to compensate for the effects that both temperature decrease and crystallinity development determine on density during solidification.The cooling stage starts at the solidification of a thin section at cavity entrance (gate),starting from that instant no more material can enter or exit from the mold impression and holding pressure can be released.When the solid layer on the mold surface reaches a thickness sufficient to assure required rigidity,the product is ejected from the mold.Due to the thermomechanical history experienced by the polymer during processing,macromolecules in injection-molded objects present a local order.This order is referred to as‘morphology’which literally means‘the study of the form’where form stands for the shape and arrangement of parts of the object.When referred to polymers,the word morphology is adopted to indicate:–crystallinity,which is the relative volume occupied by each of the crystalline phases,including mesophases;–dimensions,shape,distribution and orientation of the crystallites;–orientation of amorphous phase.R.Pantani et al./Prog.Polym.Sci.30(2005)1185–1222 1186R.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221187Apart from the scientific interest in understandingthe mechanisms leading to different order levels inside a polymer,the great technological importance of morphology relies on the fact that polymer character-istics (above all mechanical,but also optical,electrical,transport and chemical)are to a great extent affected by morphology.For instance,crystallinity has a pro-nounced effect on the mechanical properties of the bulk material since crystals are generally stiffer than amorphous material,and also orientation induces anisotropy and other changes in mechanical properties.In this work,a thorough analysis of the effect of injection molding operative conditions on morphology distribution in moldings with particular reference to crystalline materials is performed.The aim of the paper is twofold:first,to outline the state of the art on the subject;second,to present an example of the characterization required for asatisfactorilyR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221188understanding and description of the phenomena, starting from material description,passing through the monitoring of the process cycle and arriving to a deep analysis of morphology distribution inside the mold-ings.To these purposes,fully characterized injection molding tests were performed using an isotactic polypropylene,previously carefully characterized as far as most of properties of interest,in particular quiescent nucleation density,spherulitic growth rate and rheological properties(viscosity and relaxation time)were determined.The resulting moldings mor-phology(in terms of distribution of crystallinity degree, molecular orientation and crystals structure and dimensions)was analyzed by adopting different experimental techniques(optical,electronic and atomic force microscopy,IR and WAXS analysis).Final morphological characteristics of the samples were compared with the predictions of a simulation code developed at University of Salerno for the simulation of the injection molding process.The effects of both injectionflow rate and mold temperature were analyzed.1.1.Morphology distribution in injection molded iPP parts:state of the artFrom many experimental observations,it is shown that a highly oriented lamellar crystallite microstructure, usually referred to as‘skin layer’forms close to the surface of injection molded articles of semi-crystalline polymers.Far from the wall,the melt is allowed to crystallize three dimensionally to form spherulitic structures.Relative dimensions and morphology of both skin and core layers are dependent on local thermo-mechanical history,which is characterized on the surface by high stress levels,decreasing to very small values toward the core region.As a result,the skin and the core reveal distinct characteristics across the thickness and also along theflow path[1].Structural and morphological characterization of the injection molded polypropylene has attracted the interest of researchers in the past three decades.In the early seventies,Kantz et al.[2]studied the morphology of injection molded iPP tensile bars by using optical microscopy and X-ray diffraction.The microscopic results revealed the presence of three distinct crystalline zones on the cross-section:a highly oriented non-spherulitic skin;a shear zone with molecular chains oriented essentially parallel to the injection direction;a spherulitic core with essentially no preferred orientation.The X-ray diffraction studies indicated that the skin layer contains biaxially oriented crystallites due to the biaxial extensionalflow at theflow front.A similar multilayered morphology was also reported by Menges et al.[3].Later on,Fujiyama et al.[4] investigated the skin–core morphology of injection molded iPP samples using X-ray Small and Wide Angle Scattering techniques,and suggested that the shear region contains shish–kebab structures.The same shish–kebab structure was observed by Wenig and Herzog in the shear region of their molded samples[5].A similar investigation was conducted by Titomanlio and co-workers[6],who analyzed the morphology distribution in injection moldings of iPP. They observed a skin–core morphology distribution with an isotropic spherulitic core,a skin layer characterized by afine crystalline structure and an intermediate layer appearing as a dark band in crossed polarized light,this layer being characterized by high crystallinity.Kalay and Bevis[7]pointed out that,although iPP crystallizes essentially in the a-form,a small amount of b-form can be found in the skin layer and in the shear region.The amount of b-form was found to increase by effect of high shear rates[8].A wide analysis on the effect of processing conditions on the morphology of injection molded iPP was conducted by Viana et al.[9]and,more recently, by Mendoza et al.[10].In particular,Mendoza et al. report that the highest level of crystallinity orientation is found inside the shear zone and that a high level of orientation was also found in the skin layer,with an orientation angle tilted toward the core.It is rather difficult to theoretically establish the relationship between the observed microstructure and processing conditions.Indeed,a model of the injection molding process able to predict morphology distribution in thefinal samples is not yet available,even if it would be of enormous strategic importance.This is mainly because a complete understanding of crystallization kinetics in processing conditions(high cooling rates and pressures,strong and complexflowfields)has not yet been reached.In this section,the most relevant aspects for process modeling and morphology development are identified. In particular,a successful path leading to a reliable description of morphology evolution during polymer processing should necessarily pass through:–a good description of morphology evolution under quiescent conditions(accounting all competing crystallization processes),including the range of cooling rates characteristic of processing operations (from1to10008C/s);R.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221189–a description capturing the main features of melt morphology(orientation and stretch)evolution under processing conditions;–a good coupling of the two(quiescent crystallization and orientation)in order to capture the effect of crystallinity on viscosity and the effect offlow on crystallization kinetics.The points listed above outline the strategy to be followed in order to achieve the basic understanding for a satisfactory description of morphology evolution during all polymer processing operations.In the following,the state of art for each of those points will be analyzed in a dedicated section.1.1.1.Modeling of the injection molding processThefirst step in the prediction of the morphology distribution within injection moldings is obviously the thermo-mechanical simulation of the process.Much of the efforts in the past were focused on the prediction of pressure and temperature evolution during the process and on the prediction of the melt front advancement [11–15].The simulation of injection molding involves the simultaneous solution of the mass,energy and momentum balance equations.Thefluid is non-New-tonian(and viscoelastic)with all parameters dependent upon temperature,pressure,crystallinity,which are all function of pressibility cannot be neglected as theflow during the packing/holding step is determined by density changes due to temperature, pressure and crystallinity evolution.Indeed,apart from some attempts to introduce a full 3D approach[16–19],the analysis is currently still often restricted to the Hele–Shaw(or thinfilm) approximation,which is warranted by the fact that most injection molded parts have the characteristic of being thin.Furthermore,it is recognized that the viscoelastic behavior of the polymer only marginally influences theflow kinematics[20–22]thus the melt is normally considered as a non-Newtonian viscousfluid for the description of pressure and velocity gradients evolution.Some examples of adopting a viscoelastic constitutive equation in the momentum balance equations are found in the literature[23],but the improvements in accuracy do not justify a considerable extension of computational effort.It has to be mentioned that the analysis of some features of kinematics and temperature gradients affecting the description of morphology need a more accurate description with respect to the analysis of pressure distributions.Some aspects of the process which were often neglected and may have a critical importance are the description of the heat transfer at polymer–mold interface[24–26]and of the effect of mold deformation[24,27,28].Another aspect of particular interest to the develop-ment of morphology is the fountainflow[29–32], which is often neglected being restricted to a rather small region at theflow front and close to the mold walls.1.1.2.Modeling of the crystallization kineticsIt is obvious that the description of crystallization kinetics is necessary if thefinal morphology of the molded object wants to be described.Also,the development of a crystalline degree during the process influences the evolution of all material properties like density and,above all,viscosity(see below).Further-more,crystallization kinetics enters explicitly in the generation term of the energy balance,through the latent heat of crystallization[26,33].It is therefore clear that the crystallinity degree is not only a result of simulation but also(and above all)a phenomenon to be kept into account in each step of process modeling.In spite of its dramatic influence on the process,the efforts to simulate the injection molding of semi-crystalline polymers are crude in most of the commercial software for processing simulation and rather scarce in the fleur and Kamal[34],Papatanasiu[35], Titomanlio et al.[15],Han and Wang[36],Ito et al.[37],Manzione[38],Guo and Isayev[26],and Hieber [25]adopted the following equation(Kolmogoroff–Avrami–Evans,KAE)to predict the development of crystallinityd xd tZð1K xÞd d cd t(1)where x is the relative degree of crystallization;d c is the undisturbed volume fraction of the crystals(if no impingement would occur).A significant improvement in the prediction of crystallinity development was introduced by Titoman-lio and co-workers[39]who kept into account the possibility of the formation of different crystalline phases.This was done by assuming a parallel of several non-interacting kinetic processes competing for the available amorphous volume.The evolution of each phase can thus be described byd x id tZð1K xÞd d c id t(2)where the subscript i stands for a particular phase,x i is the relative degree of crystallization,x ZPix i and d c iR.Pantani et al./Prog.Polym.Sci.30(2005)1185–1222 1190is the expectancy of volume fraction of each phase if no impingement would occur.Eq.(2)assumes that,for each phase,the probability of the fraction increase of a single crystalline phase is simply the product of the rate of growth of the corresponding undisturbed volume fraction and of the amount of available amorphous fraction.By summing up the phase evolution equations of all phases(Eq.(2))over the index i,and solving the resulting differential equation,one simply obtainsxðtÞZ1K exp½K d cðtÞ (3)where d c Z Pid c i and Eq.(1)is recovered.It was shown by Coccorullo et al.[40]with reference to an iPP,that the description of the kinetic competition between phases is crucial to a reliable prediction of solidified structures:indeed,it is not possible to describe iPP crystallization kinetics in the range of cooling rates of interest for processing(i.e.up to several hundreds of8C/s)if the mesomorphic phase is neglected:in the cooling rate range10–1008C/s, spherulite crystals in the a-phase are overcome by the formation of the mesophase.Furthermore,it has been found that in some conditions(mainly at pressures higher than100MPa,and low cooling rates),the g-phase can also form[41].In spite of this,the presence of different crystalline phases is usually neglected in the literature,essentially because the range of cooling rates investigated for characterization falls in the DSC range (well lower than typical cooling rates of interest for the process)and only one crystalline phase is formed for iPP at low cooling rates.It has to be noticed that for iPP,which presents a T g well lower than ambient temperature,high values of crystallinity degree are always found in solids which passed through ambient temperature,and the cooling rate can only determine which crystalline phase forms, roughly a-phase at low cooling rates(below about 508C/s)and mesomorphic phase at higher cooling rates.The most widespread approach to the description of kinetic constant is the isokinetic approach introduced by Nakamura et al.According to this model,d c in Eq.(1)is calculated asd cðtÞZ ln2ðt0KðTðsÞÞd s2 435n(4)where K is the kinetic constant and n is the so-called Avrami index.When introduced as in Eq.(4),the reciprocal of the kinetic constant is a characteristic time for crystallization,namely the crystallization half-time, t05.If a polymer is cooled through the crystallization temperature,crystallization takes place at the tempera-ture at which crystallization half-time is of the order of characteristic cooling time t q defined ast q Z D T=q(5) where q is the cooling rate and D T is a temperature interval over which the crystallization kinetic constant changes of at least one order of magnitude.The temperature dependence of the kinetic constant is modeled using some analytical function which,in the simplest approach,is described by a Gaussian shaped curve:KðTÞZ K0exp K4ln2ðT K T maxÞ2D2(6)The following Hoffman–Lauritzen expression[42] is also commonly adopted:K½TðtÞ Z K0exp KUÃR$ðTðtÞK T NÞ!exp KKÃ$ðTðtÞC T mÞ2TðtÞ2$ðT m K TðtÞÞð7ÞBoth equations describe a bell shaped curve with a maximum which for Eq.(6)is located at T Z T max and for Eq.(7)lies at a temperature between T m(the melting temperature)and T N(which is classically assumed to be 308C below the glass transition temperature).Accord-ing to Eq.(7),the kinetic constant is exactly zero at T Z T m and at T Z T N,whereas Eq.(6)describes a reduction of several orders of magnitude when the temperature departs from T max of a value higher than2D.It is worth mentioning that only three parameters are needed for Eq.(6),whereas Eq.(7)needs the definition offive parameters.Some authors[43,44]couple the above equations with the so-called‘induction time’,which can be defined as the time the crystallization process starts, when the temperature is below the equilibrium melting temperature.It is normally described as[45]Dt indDtZðT0m K TÞat m(8)where t m,T0m and a are material constants.It should be mentioned that it has been found[46,47]that there is no need to explicitly incorporate an induction time when the modeling is based upon the KAE equation(Eq.(1)).1.1.3.Modeling of the morphology evolutionDespite of the fact that the approaches based on Eq.(4)do represent a significant step toward the descriptionR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221191of morphology,it has often been pointed out in the literature that the isokinetic approach on which Nakamura’s equation (Eq.(4))is based does not describe details of structure formation [48].For instance,the well-known experience that,with many polymers,the number of spherulites in the final solid sample increases strongly with increasing cooling rate,is indeed not taken into account by this approach.Furthermore,Eq.(4)describes an increase of crystal-linity (at constant temperature)depending only on the current value of crystallinity degree itself,whereas it is expected that the crystallization rate should depend also on the number of crystalline entities present in the material.These limits are overcome by considering the crystallization phenomenon as the consequence of nucleation and growth.Kolmogoroff’s model [49],which describes crystallinity evolution accounting of the number of nuclei per unit volume and spherulitic growth rate can then be applied.In this case,d c in Eq.(1)is described asd ðt ÞZ C m ðt 0d N ðs Þd s$ðt sG ðu Þd u 2435nd s (9)where C m is a shape factor (C 3Z 4/3p ,for spherical growth),G (T (t ))is the linear growth rate,and N (T (t ))is the nucleation density.The following Hoffman–Lauritzen expression is normally adopted for the growth rateG ½T ðt Þ Z G 0exp KUR $ðT ðt ÞK T N Þ!exp K K g $ðT ðt ÞC T m Þ2T ðt Þ2$ðT m K T ðt ÞÞð10ÞEqs.(7)and (10)have the same form,however the values of the constants are different.The nucleation mechanism can be either homo-geneous or heterogeneous.In the case of heterogeneous nucleation,two equations are reported in the literature,both describing the nucleation density as a function of temperature [37,50]:N ðT ðt ÞÞZ N 0exp ½j $ðT m K T ðt ÞÞ (11)N ðT ðt ÞÞZ N 0exp K 3$T mT ðt ÞðT m K T ðt ÞÞ(12)In the case of homogeneous nucleation,the nucleation rate rather than the nucleation density is function of temperature,and a Hoffman–Lauritzen expression isadoptedd N ðT ðt ÞÞd t Z N 0exp K C 1ðT ðt ÞK T N Þ!exp KC 2$ðT ðt ÞC T m ÞT ðt Þ$ðT m K T ðt ÞÞð13ÞConcentration of nucleating particles is usually quite significant in commercial polymers,and thus hetero-geneous nucleation becomes the dominant mechanism.When Kolmogoroff’s approach is followed,the number N a of active nuclei at the end of the crystal-lization process can be calculated as [48]N a ;final Zðt final 0d N ½T ðs Þd sð1K x ðs ÞÞd s (14)and the average dimension of crystalline structures can be attained by geometrical considerations.Pantani et al.[51]and Zuidema et al.[22]exploited this method to describe the distribution of crystallinity and the final average radius of the spherulites in injection moldings of polypropylene;in particular,they adopted the following equationR Z ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi3x a ;final 4p N a ;final 3s (15)A different approach is also present in the literature,somehow halfway between Nakamura’s and Kolmo-goroff’s models:the growth rate (G )and the kinetic constant (K )are described independently,and the number of active nuclei (and consequently the average dimensions of crystalline entities)can be obtained by coupling Eqs.(4)and (9)asN a ðT ÞZ 3ln 24p K ðT ÞG ðT Þ 3(16)where heterogeneous nucleation and spherical growth is assumed (Avrami’s index Z 3).Guo et al.[43]adopted this approach to describe the dimensions of spherulites in injection moldings of polypropylene.1.1.4.Modeling of the effect of crystallinity on rheology As mentioned above,crystallization has a dramatic influence on material viscosity.This phenomenon must obviously be taken into account and,indeed,the solidification of a semi-crystalline material is essen-tially caused by crystallization rather than by tempera-ture in normal processing conditions.Despite of the importance of the subject,the relevant literature on the effect of crystallinity on viscosity isR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221192rather scarce.This might be due to the difficulties in measuring simultaneously rheological properties and crystallinity evolution during the same tests.Apart from some attempts to obtain simultaneous measure-ments of crystallinity and viscosity by special setups [52,53],more often viscosity and crystallinity are measured during separate tests having the same thermal history,thus greatly simplifying the experimental approach.Nevertheless,very few works can be retrieved in the literature in which(shear or complex) viscosity can be somehow linked to a crystallinity development.This is the case of Winter and co-workers [54],Vleeshouwers and Meijer[55](crystallinity evolution can be drawn from Swartjes[56]),Boutahar et al.[57],Titomanlio et al.[15],Han and Wang[36], Floudas et al.[58],Wassner and Maier[59],Pantani et al.[60],Pogodina et al.[61],Acierno and Grizzuti[62].All the authors essentially agree that melt viscosity experiences an abrupt increase when crystallinity degree reaches a certain‘critical’value,x c[15]. However,little agreement is found in the literature on the value of this critical crystallinity degree:assuming that x c is reached when the viscosity increases of one order of magnitude with respect to the molten state,it is found in the literature that,for iPP,x c ranges from a value of a few percent[15,62,60,58]up to values of20–30%[58,61]or even higher than40%[59,54,57].Some studies are also reported on the secondary effects of relevant variables such as temperature or shear rate(or frequency)on the dependence of crystallinity on viscosity.As for the effect of temperature,Titomanlio[15]found for an iPP that the increase of viscosity for the same crystallinity degree was higher at lower temperatures,whereas Winter[63] reports the opposite trend for a thermoplastic elasto-meric polypropylene.As for the effect of shear rate,a general agreement is found in the literature that the increase of viscosity for the same crystallinity degree is lower at higher deformation rates[62,61,57].Essentially,the equations adopted to describe the effect of crystallinity on viscosity of polymers can be grouped into two main categories:–equations based on suspensions theories(for a review,see[64]or[65]);–empirical equations.Some of the equations adopted in the literature with regard to polymer processing are summarized in Table1.Apart from Eq.(17)adopted by Katayama and Yoon [66],all equations predict a sharp increase of viscosity on increasing crystallinity,sometimes reaching infinite (Eqs.(18)and(21)).All authors consider that the relevant variable is the volume occupied by crystalline entities(i.e.x),even if the dimensions of the crystals should reasonably have an effect.1.1.5.Modeling of the molecular orientationOne of the most challenging problems to present day polymer science regards the reliable prediction of molecular orientation during transformation processes. Indeed,although pressure and velocity distribution during injection molding can be satisfactorily described by viscous models,details of the viscoelastic nature of the polymer need to be accounted for in the descriptionTable1List of the most used equations to describe the effect of crystallinity on viscosityEquation Author Derivation Parameters h=h0Z1C a0x(17)Katayama[66]Suspensions a Z99h=h0Z1=ðx K x cÞa0(18)Ziabicki[67]Empirical x c Z0.1h=h0Z1C a1expðK a2=x a3Þ(19)Titomanlio[15],also adopted byGuo[68]and Hieber[25]Empiricalh=h0Z expða1x a2Þ(20)Shimizu[69],also adopted byZuidema[22]and Hieber[25]Empiricalh=h0Z1Cðx=a1Þa2=ð1Kðx=a1Þa2Þ(21)Tanner[70]Empirical,basedon suspensionsa1Z0.44for compact crystallitesa1Z0.68for spherical crystallitesh=h0Z expða1x C a2x2Þ(22)Han[36]Empiricalh=h0Z1C a1x C a2x2(23)Tanner[71]Empirical a1Z0.54,a2Z4,x!0.4h=h0Zð1K x=a0ÞK2(24)Metzner[65],also adopted byTanner[70]Suspensions a Z0.68for smooth spheresR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221193。

专利名称：聚苯乙烯作为基底的生物敏感膜及其制备方法专利类型：发明专利
发明人：隋森芳,杨军
申请号：CN98117828.6
申请日：19980828
公开号：CN1211505A
公开日：
19990324
专利内容由知识产权出版社提供
摘要：本发明属于生物工程技术领域,在疏水性载体表面上结合一层聚苯乙烯薄膜组成生物敏感膜。

其制备方法包括:在去离子水形成的平静液面上滴加聚苯乙烯氯仿溶液,待氯仿挥发后聚苯乙烯在空气/水界面形成均匀薄层,将该薄层用LB膜方法水平转移到疏水性的载体表面。

本发明不但工艺简单,成本低廉,有利于推广,而且它可以作为很好的受体蛋白载体,其SPR测量精度至少比ELISA高两个数量级。

申请人：清华大学
地址：100084 北京市海淀区清华园
国籍：CN
代理机构：清华大学专利事务所
代理人：廖元秋
更多信息请下载全文后查看。

Section 10EmulsionsBy Drs. Pardeep K. Gupta, Clyde M. Ofner and Roger L. SchnaareTable of Contents Emulsions (1)Table of Contents (1)Introduction and Background (3)Definitions (3)Types of Emulsions (3)Formation of an Emulsion (4)Determination of Emulsion Type (4)Miscibility or Dilution Test (4)Staining or Dye Test (4)Electrical Conductivity Test (4)Physical State of Emulsions (5)Pharmaceutical Application of Emulsions (5)Formulations (6)Typical Ingredients (6)Drug (6)Oil Phase (6)Aqueous Phase (6)Thickening Agents (6)Sweeteners (6)Preservative (6)Buffer (7)Flavor (7)Color (7)Sequestering Agents (7)Humectants (7)Antioxidants (7)Emulsifiers (7)Guidelines (7)Type of Emulsion Desired (7)Toxicity (8)Method of Preparation (8)Typical Formulas (8)Cod Liver Oil Emulsion (polysaccharide emulsifier) (8)Protective Lotion (divalent soap emulsifier) (8)Benzoyl Benzoate Emulsion (emulsifying wax emulsifier) (8)Barrier Cream (soap emulsifier) (9)Cold Cream (soap emulsifier) (9)All Purpose Cream (synthetic surfactant emulsifier) (9)Emulsifiers (10)Natural Products (10)Polysaccharides (10)Sterols (10)Phospholipids (10)Surfactants (10)Anionic Surfactants (11)Soaps (11)Detergents (11)Cationic Surfactants (11)Nonionic Surfactants (11)Finely Divided Solids (12)Methods to Prepare Emulsions (13)Classical Gum Methods (13)Dry Gum Method (13)Wet Gum Method (13)“In Situ” Soap Method (13)Lime Water/Vegetable Oil Emulsions (13)Other Soaps (13)With Synthetic Surfactants (13)Required HLB of the Oil Phase (14)HLB of Surfactant Mixtures (14)Emulsion Stability (15)Sedimentation or Creaming (15)Factors - Stoke’s Law (15)Droplet Size (15)Density Difference (15)The Gravitational Constant, g (15)Viscosity (15)Breaking or Cracking (16)Thermodynamics of Emulsions (17)Microemulsions (18)References (19)Selected Readings (19)Introduction and BackgroundDefinitionsEmulsions are pharmaceutical preparations consisting of at least two immiscible liquids.Due to the lack of mutual solubility, one liquid is dispersed as tiny droplets in the other liquid to form an emulsion. Therefore,emulsions belong to the group of prepara-tions known as disperse systems.The USP also defines several dosage forms that are essentially emulsions but historically are referred to by other names. For example;Lotions are fluid emulsions orsuspensions intended for external application.Creams are viscous liquid or semi-solid emulsions of either an oil-in-water (O/W) or the water-in-oil (W/O) type. They are ordinarily used topically. The term cream is applied most frequently to soft, cosmetically acceptable types of preparations.Microemulsions are emulsions withextremely small droplet sizes and usually require a high concentration of surfactant for stability. They can also be regarded as isotropic, swollen micellar systems.Multiple emulsions are emulsions that have been emulsified a second time,consequently containing three phases. They may be water-in-oil-in-water (W/O/W) or oil-in-water-in-oil (O/W/O).Fluid emulsions are generally composed of discrete, observable liquid droplets in a fluid media, while semi-solid emulsions generally have a complex, more disorganized structure.The liquid which is dispersed as droplets iscalled as the dispersed , discontinuous or internal phase, and the liquid in which thedispersion is suspended is the dispersion medium or the continuous or external phase.For example, if olive oil is shaken with water,it breaks up into small globules andbecomes dispersed in water. In this case the oil is the internal phase, and water is the external phase.The dispersed particles or globules can range in size from less than 1 µm up to 100 µm. An emulsion is rarely a monodis-perse system, e.g., all the particles are rarely of the same size. A typical emulsion contains a distribution of many sizes, making it a polydisperse system.Types of EmulsionsBased on the nature of the internal (or exter-nal) phase, emulsions are of two types; oil-in-water (O/W) and water-in-oil (W/O). In an O/W type the oil phase is dispersed in the aqueous phase, while the opposite is true in W/O emulsions. Figure 1 depicts these two types of emulsions.Figure 1: Representation of Two Types of EmulsionsO/W Emulsion W/O Emulsion (water black)(oil white)When two immiscible phases are shaken together, either type of emulsion can result.However, this result is not random, but is dependent primarily on two factors; most importantly the type of emulsifier used and secondly the relative ratio of the aqueous and oil phases (phase volume ratio). The emulsifiers and their role in the type of emulsion are discussed in detail later in this chapter.In terms of the phase volume ratio, the percent of the internal phase is generally less than 50%, although emulsions can have internal phase volume percent as high as 75%. Uniform spheres, when packed in a rhombohedral geometry occupy approxi-mately 75% of the total volume. Phase volumes higher than 75% require that the droplets of dispersed phase be distorted into geometric shapes other than perfect spheres. Although it is rare to find emulsions with higher than 75% internal volume, phase volumes of over 90% have been reportedin literature.Formation of an EmulsionWhen two immiscible liquids are placedin contact with each other, they form two separate layers. The liquid with higher density forms the lower layer and the one with lower density forms the upper layer. When this two-layer system is shaken vigorously, one of the layers disperses in the other liquid forming an unstable emul-sion. If left unstirred, the dispersed phase comes together and coalesces into larger drops until the layers become separate again. If no other ingredient is added, this process of separation is usually completein a matter of a few minutes to a few hours. Therefore, a liquid dispersion is inherently an unstable system.However, when an emulsifier is present in the system, it reduces the interfacial tension between the two liquids and forms a physical barrier between droplets, hence lowers the total energy of the system(see discussion on Thermodynamics of Emulsions), thereby reducing the tendency of the droplets to come together and coalesce. Consequently, the globules ofthe internal phase may remain intact for long periods of time, forming a “stable”emulsion. It should be noted, however,that even with an emulsifier, an emulsionis a thermodynamically unstable system and will eventually revert to bulk phases. The time required for this process is determined by kinetics.Determination of Emulsion TypeSeveral tests can be used to determine whether a given emulsion is an O/W or W/O type. These are as follows:Miscibility or Dilution TestThis method is based on the fact that an emulsion can be diluted freely with a liquid of the same kind as its external phase. Typically, a small amount of the emulsion is added to a relatively large volume of water and the mixture is stirred. If the emulsion disperses in water, it is considered to bean O/W type emulsion. If, however, the emulsion remains undispersed, it is a W/O type emulsion.Staining or Dye TestThis test is based on the fact that if a dye is added to an emulsion and the dye is soluble only in the internal phase, the emulsion contains colored droplets dispersed inthe colorless external phase. This can be confirmed by observing a drop of emulsion under a low power microscope. An example of such a dye is scarlet red, which is an oil soluble dye. When added to an O/W type emulsion, followed by observation under the microscope, bright red colored oil drops in an aqueous phase can be seen clearly. Electrical Conductivity TestThis test is based on the fact that onlythe aqueous phase can conduct electrical current. Thus, when a voltage is applied across a liquid, a significant amount of electrical current will flow only when the path of the current is through a continuous aqueous phase. Since oil is a non-conductor of electricity, when tested for conductivity, a W/O type emulsion will show insignificant current flow.Often times a single test may not be conclu-sive. In such circumstances, more than one test may need to be carried out to confirm the emulsion type.Physical State of EmulsionsMost emulsions are either liquid or semi-solid at room temperature. In general, due to their high viscosity, the semi-solid emulsions are relatively more physically stable. Liquid emulsions are more commonly compounded for internal use, while semisolids are usually for external use or for use in body cavities (rectal or vaginal).Other terms commonly used to describe emulsions are lotion and cream . The term lotion refers to a disperse system that flows freely under the force of gravity. A cream is a product that does not flow freely under the force of gravity. It should be noted, however,that these terms are meaningful only when the product is at room temperature. A cream product may behave like a lotion with a temperature increase of a few degrees. The physical state of the final product is also influenced by its intended use. For example suntan lotions are dispensed as lotions instead of creams because they need to be applied on large body surface. Lotion form makes it easy to pour and spread the product. For application over a small portion of skin, a cream is the preferred form of an emulsion.Pharmaceutical Applications of Emulsions There are several reasons for formulation of a product as an emulsion. These include the following:•To disguise the taste or smell of oils or oil soluble drugs. These emulsions are normally O/W types with the aqueous phase containing sweeteners and flavoring agents to mask the poor taste of oils. An O/W type of emulsionalso makes it easy to rinse off the residual dose from the mouth and does not leave an oily taste. Mineral oil and cod liver oil are emulsified for this reason.•To improve the absorption of poorly soluble drugs. Oil soluble drugs may not be soluble enough to be absorbed efficiently. An example of such a drug is cyclosporin, which is dispensed as a microemulsion. •To deliver nutrients and vitamins by intravenous injection. Intralipid is an emulsion product for administering an oil by the IV route.•To serve as a vehicle for the topical administration of a variety of drugs.Kb is the binding constant of the preservative with the surfactantSweeteners are added to emulsions to produce a more palatable preparation, toand sorbitol.AntioxidantsAntioxidants are often added to prevent oxidation of vegetable oils and/or the active drug.Table 1. Typical AntioxidantsEmulsifiersEmulsifiers are substances that have the ability to concentrate at the surface of a liquid or interface of two liquids, many of them reducing the surface or interfacial tension. Those emulsifiers that reduce surface tension are also called surfactants .Emulsifiers in general are discussed inmore detail in a later section of this chapter.GuidelinesBefore selecting a formula for an emulsion,one needs to consider several factors.These are listed below.Type of Emulsion DesiredSince O/W emulsions are more pleasant to touch and swallow, they are generally preferred. Preparations for internal use are almost always O/W type products.Externally used emulsions may be of either type. Creams and lotions that are used primarily to provide oil to the skin need to be W/O due to high concentration of oils in these preparations.The equation shows that the effective concentration in the aqueous phase will always be a fraction of the total concentration.Solvents such as alcohol, glycerin and propylene glycol are often used as apreservative at concentrations approaching 10%. See Table 5, Typical Preservatives in Section 9 of this manual.BufferMany chemical buffer systems have been used in emulsions to control the pH. The optimal pH is chosen to ensure activity of the emulsifier, control stability of the drug and to ensure compatibility and stability of other ingredients.FlavorFlavoring agents enhance patient accept-ance of the product, which is particularly important for pediatric patients.ColorColorants are intended to provide a more aesthetic appearance to the final product.Emulsions are generally not colored with the exception of some topical products. Sequestering AgentsSequestering agents may be necessary to bind metal ions in order to control oxidative degradation of either the drug or other ingredients. HumectantsHumectants are water soluble polyols that prevent or hinder the loss of water from semi-solid emulsions, i.e., topical creams.They also contribute to the solvent proper-ties of the aqueous phase and contribute to the sweetness of oral preparations. The most common are glycerin, propylene glycolToxicityMost emulsifiers are not suitable for internal use. For orally given emulsions, acacia is commonly used as an emulsifying agent.Taste is another factor in selection ofingredients. In this regard, most polysaccha-rides are tasteless and, hence, suitable from a taste standpoint.Method of PreparationSoaps and acacia are excellent forextemporaneous preparations. While soaps allow the preparation to be made by simply mixing the ingredients and shaking, acacia can be used in a pestle and mortar to prepare emulsions.Typical FormulasCod Liver Oil Emulsion (polysaccharide emulsifier)Preparationing a ratio of 4:2:1 for oil, water and gums(both combined), prepare a primary emulsion by dry gum method. (See Methods to Prepare Emulsions on page 13.)2.Dilute with water to a flowable consistency andpour in a measuring device.3.Add alcohol diluted with equal volume of water,followed by the benzaldehyde and saccharin sodium.4.Dilute to volume (200 mL) with waterPreparation1.Add benzyl benzoate to the wax in a beakerand heat in a water bath until the wax melts and the temperature reaches 60°C.2.In a separate beaker, add an appropriate volumeof water and heat to the same temperature.3.Add the water to the oil phase with continuousstirring.4.Continue to stir until the mixture begins tothicken and cools to room temperature.Preparation1.Mix the two powders in a mortar and trituratewell, taking care that all the lumps and large particles have been reduced.2.Then add oil slowly with constant trituration untilall the oil has been added. Triturate to form a smooth paste.3.Then add the limewater and triturate briskly toform the emulsion.Note: The emulsifier, calcium oleate (from limewater and olive oil), preferentially forms O/W emulsions.Protective Lotion (divalent soap emulsifier)Benzyl Benzoate Emulsion (emulsifying wax emulsifier)Preparation1.Mix the paraffins, cetostearyl alcohol andstearic acid in a beaker and heat in a water bath to about 60°C.2.Heat water and chlorocresol together to thesame temperature.3.Add the aqueous phase to the oil phase andstir until congealed and cooled to room temperature.Note:The emulsifier is triethanolamine stearate formed in situ.Preparation1.Melt the sorbitan monostearate and stearicacid in the liquid paraffin and cool to 60°C. 2.Mix the sorbitol solution, preservatives,polysorbate 60 and water and heat to the temperature of the oil mixture.3.Add the aqueous solution to the oil phase andstir until it has congealed and cooled to room temperature.Note:Propylene glycol serves as a solvent for the preservatives.Preparation1.Mix and melt the wax and paraffin together.2.Dissolve borax in water and heat both containerson a water bath to 70°C.3.Add the aqueous phase to the oil phase andstir until it has congealed and cooled to room temperature.Note:The fatty acid in white beeswax reacts with borax (sodium borate) to make a sodium soap which acts as an W/O type emulsifier.Barrier Cream (soap emulsifier)All Purpose Cream (synthetic surfactant emulsifier)Cold Cream (soap emulsifier)Surfactants or surface active agents are molecules that consist of two distinct parts,a hydrophobic tail and a hydrophilic head group. They are generally classified based on the hydrophilic properties of the head group (ionic charge, polarity, etc.). Since the hydrophobic chains do not vary much in their properties, the nature of surfactants is dependent mainly on the head group structure.A common problem with sterol-containing emulsifiers is that being complex mixtures of natural substances, they are prone to variability in their quality and, hence, performance. Also, these agents usually contain some degree of an odor, which varies with the purity and source. Some semi-synthetic substitutes are available that seek to overcome some of the problems associated with these agents.There are of basically three types of emulsifiers: natural products, surface active agents (surfactants), and finely divided solids. Based on whether a stable emulsion can be produced, emulsifiers are also classified either as primary emulsifying agents which produce stable emulsions by themselves, or secondary emulsifying agents (stabilizers) which help primary emulsifiers to form a more stable emulsion.of cholesterol. Cholesterol itself is a very efficient emulsifier and produces W/O type emulsions. Consequently, its use is limited to topical preparations such as Hydrophilic Petrolatum USP which readily absorbs water forming a W/O cream. Woolfat or lanolin contains a considerable amount of choles-terol esters and can absorb up to 50% of its own weight of water.This group of emulsifiers, which numbers in the hundreds, contain a polyoxyethylene chain as the polar head group. They arenonionic and, thus, are compatible with ionic compounds and are less susceptible to pH changes. There are several such surfactants official in the USP/NF , typified by sorbitan monooleate (a partial ester of lauric acid with sorbitol), polysorbate 80(polyoxyethyl-ene 20 sorbitan monooleate) which contains 20 oxyethylene units copolymerized sorbitanAmine soaps consist of an amine, such as triethanolamine, in the presence of a fatty acid. These surfactants are viscous solutions and produce O/W type emulsions. They offer the advantage that the final pH of the preparations is generally close to neutral,and, therefore, allows their use on skin for extended periods of time.monooleate) and polyoxyl 40 stearate(a mixture of stearic acid esters with mixed poloxyethylene diols equivalent to about40 oxyethylene units).The large number of nonionic emulsifiers results from the large number of possible combinations of various alkyl groups with polyoxyethylene chains of varying lengths. Compounds with saturated and/or large alkyl groups, such as stearyl, tend to be solids or semisolids while oleyl (also large, but unsaturated) compounds tend to be liquids. Also, the longer the polyoxyethylene chain, the higher the melting point.To characterize such a large number of compounds, they are each assigned an HLB number. The HLB number or hydrophile-lipophile balance, is a measure of the relative hydrophilic vs lipophilic character of the molecule as determined by the relative size of the polyoxyethylene chain vs the alkyl group. HLB numbers range from 0 for a pure hydrocarbon to 20 for a pure poly-oxyethylene chain. Some typical valuesare listed in Table 3.Ionic surfactants, such as sodium lauryl sulfate, were not included in the original definition of the HLB system but have been included as the HLB system was developed. The HLB number of 40 for sodium lauryl sulfate is outside of the range of 0 to 20 and simply means that sodium lauryl sulfate is much more soluble or hydrophilic thana pure polyoxyethylene chain.Table 3. Typical HLB Numbersof EmulsifiersFinely Divided SolidsFinely divided solids function as emulsifiers because of their small particle size. Fine particles tend to concentrate at a liquid-liquid interface, depending on their wetability, and form a particulate film around the dispersed droplets. They are seldom used as the primary emulsifier.phase. The emulsion type will depend on the type of soap formed.Basically the formula is divided into anoil phase and an aqueous phase with the ingredients dissolved in their proper phases (oil or water). The surfactant(s) is added to the phase in which it is most soluble. The oil phase is then added to the aqueous phase with mixing, and the coarse mixture passed through an homogenizer.When waxes or waxy solids are included in the formulation, the use of heat is necessary,as described above.Required HLB of the Oil Phase.It has been found that various oils and lipid materials form stable emulsions withsurfactants that have a certain HLB value.This HLB value is called the required HLB of the oil or lipid. Theoretically, any surfac-tant with the required HLB would produce a stable emulsion with the indicated oil or lipid. Some examples are given in Table 4.Table 4. Required HLB Values for Typical Oils and LipidsHLB of Surfactant MixturesIt may be difficult to find a surfactant with the exact HLB number required for a given oil phase in an emulsion. Fortunately, the HLB numbers have been shown to be additive for a mixture of surfactants. Thus, if one required a surfactant with a HLB of 10, one could use a mixture of sorbitan monooleate (HLB = 4.7) and polysorbate 80 (HLB = 15.6). Such a mixture can be calculated on the basis of a simple weighted average as follows.Suppose 5 g of surfactant mixture is required. Let ␹= the g of sorbitanmonooleate, then 5 ␹= the g of polysorbate 80 required.␹(4.7)+(5- ␹)(15.6) = 10(5)4.7 ␹+ 78.0- 15.6␹= 10(5)10.9␹= 28␹= 2.57 and 5- ␹= 2.43Thus a mixture of 2.57 g of sorbitanmonooleate and 2.43 g of polysorbate 80would have a HLB of 10.Griffin 2described an experimental approach for the formulation of emulsions using synthetic emulsifiers.1.Group the ingredients on the basis of theirsolubilities in the aqueous and oil phases.2.Determine the type of emulsion required andcalculate an approximate required HLB value.3.Blend a low HLB emulsifier and a high HLBemulsifier to the required HLB.4.Dissolve the oil soluble ingredients and the lowHLB emulsifier in the oil phase. Heat, if necessary,to approximately 5 to 10°over the melting point of the highest melting ingredient or to a maximum temperature of 70 to 80°C.5.Dissolve the water soluble ingredients (exceptacids and salts) in a sufficient quantity of water.6.Heat the aqueous phase to a temperature whichis 3 to 5°higher than that of the oil phase.7.Add the aqueous phase to the oil phase withsuitable agitation.8.If acids or salts are employed, dissolve them inwater and add the solution to the cold emulsion.9.Examine the emulsion and make adjustments inthe formulation if the product is unstable. It may be necessary to add more emulsifier, change to an emulsifier with a slightly higher or lower HLB value or to use an emulsifier with different chemical characteristics.In addition to chemical degradation of various components of an emulsion, which can happen in any liquid preparation, emulsions are subject to a variety of physical instabilities. Sedimentation or Creaming Factors - Stoke’s LawCreaming usually occurs in a liquid emulsion since the particle size is generally greater than that of a colloidal dispersion. The rate is described by Stoke’s Law for a single particle settling in an infinite container under the force of gravity as follows:d ␹=d 2(␳2- ␳1)gdt 18␩where:d ␹/d t= the sedimentation rate in distance/time d = droplet diameter ␳2= droplet density␳1= emulsion medium density g = acceleration due to gravity ␩= viscosity of the emulsion mediumSince for most oil phases, ␳2< ␳1, then sedimentation will be negative, i.e., the oil droplets will rise forming a creamy whitelayer. While Stoke’s Law does not describe creaming quantitatively in an emulsion, it does provide a clear collection of factors and their qualitative influence on creaming.Droplet SizeReducing droplet size can have a significant effect on creaming rate. Since the diameter is squared in Stoke’s Law, a reduction in size by ¹⁄₂will reduce the creaming rate by (¹⁄₂)2or a factor of 4.Emulsion StabilityDensity DifferenceIf the difference in density between the emulsion droplet and the external phase can be matched, the creaming rate could be reduced to zero. This is almost impossi-ble with most oils and waxy solids used in emulsions.The Gravitational Constant, gThis parameter is not of much interest since it can not be controlled or changed unless in space flight.ViscosityViscosity turns out to be the most readily controllable parameter in affecting the creaming rate. While the viscosity in Stoke’s Law refers to the viscosity of the fluid through which a droplet rises, in reality the viscosity that controls creaming is the viscosity of the entire emulsion. Thus, doubling the viscosity of an emulsion will decrease the creaming rate by a factor of 2.There are three major ways to increase the viscosity of an emulsion:•Increase the concentration of the internal phase•Increase the viscosity of the internal phase by adding waxes and waxy solids to the oil phase.•Increase the viscosity of the external phase by adding a viscosity building agent. Most of the suspending agents described in the Suspensions Section in this manual have been used for this purpose.Creaming does not usually occur in a semi-solid emulsion.Breaking or CrackingThis problem arises when the dispersed globules come together and coalesce to form larger globules. As this process continues, the size of the globules increases, making it easier for them to coalesce. This eventually leads to separation of the oil and water phases. For cracking to occur, the barrier that normally holds globules apart has to break down. Some of the factorsthat contribute to cracking are as follows:•Insufficient or wrong kind of emulsifier in the system.•Addition of ingredients that inactivate the emulsifier. Incompatible ingredients may show their effect over a period of time.An example of such an incompatibilitywill be to use large anions in thepresence of cationic emulsifier.•Presence of hardness in water. The calcium and magnesium present in hard water can replace a part of the alkalisoap with divalent soap. Since thesesoaps form different kinds of emulsions, phase inversion usually takes place.•Low viscosity of the emulsion •Exposure to high temperatures can also accelerate the process of coalescence.This is due to the fact that at an elevated temperature, the collisions between theglobules can overcome the barrier tocoalescence, thereby increasing thechance that a contact between twoparticles will lead to their fusion.Temperature may have an adverse effect on the activity of emulsifiers, particularly if these are proteinaceous in nature.However, this usually happens at temper-atures higher than 50°C. Conversely, areduction in temperature to the point that the aqueous phase freezes also will break the emulsion.•An excessive amount of the internal phase makes an emulsion inherently less stable because there is a greater chance of globules coming together.Cracking is the most serious kind of physical instability of an emulsion. Cracking of an emulsion usually renders it useless. In creams, the problem of cracking may show up as tearing. This is a process where one phase separates and appears like drops on top of the cream.The basic difference between creamingand cracking is that the globules in creaming do not coalesce to form larger particles. Therefore, creaming is a less serious problem and most preparations that show creaming can be shaken to redisperse the internal phase to its original state. A com-mon example of creaming is the formation of cream on top of whole milk due to collection of emulsified fat of the milk. This problem is solved by homogenizing the milk to reduce the particle size of dispersed fat, thereby reducing the rate at which they travel tothe surface.。

大连理工大学硕士学位论文摘要活化的过硫酸盐氧化，作为一种新兴的高级氧化技术，是一种矿化难降解有毒污染物的有效方法。

在众多的活化方法中，过硫酸盐通过接受电子完成的电化学活化，具有容易操控和环境友好的特点，被认为是一种有前景的活化技术。

但在电化学活化的过程中，由于静电斥力阻碍了过硫酸盐阴离子和阴极之间的接触，导致过硫酸盐低的分解率和随后低的自由基的产生量，从而使污染物的降解效果变差。

针对此问题，本文使用天然木材衍生的碳化木（CW）制备了具有多通道的流通式阴极（FTC），通过将过一硫酸盐（PMS）阴离子限制在阴极的微通道中，能够显著地强化其与阴极的碰撞与接触，提高电化学活化的效率并增强对污染物的降解。

主要的研究成果如下：（1）通过天然松木的一步碳化制备并组装了具有丰富的介孔，良好的导电性，较高的机械强度，大量有序的微通道以及对PMS有良好的电催化活性的FTC。

以苯酚为目标污染物，探究了不同的反应条件（PMS浓度、电流密度和停留时间）对FTC电活化PMS降解苯酚性能的影响。

结果表明，在苯酚进水浓度为20 mg/L, 进水TOC=18 mg/L，进水PMS浓度为6.51 mM，背景Na2SO4为0.05 M，电流密度为2.75 mA/cm2，进水pH 2.87，停留时间10 min以及常温的条件下，通过FTC电活化PMS，PMS的分解率达到了71.9%。

苯酚和TOC的去除率分别达到了97.9%和39.6%。

EPR实验结果表明，在FTC电活化PMS的过程中，产生了大量的·OH和SO4•-。

同时，自由基淬灭实验也表明，·OH和SO4•-均参与了对苯酚的降解，且·OH对降解的贡献更大。

此外，五次循环实验的结果证明了本研究组装的FTC具有很好的稳定性。

（2）通过封闭CW的微通道，获得了流过式阴极（FBC）。

在相同的优化条件下，详细对比了在FTC中和FBC上的PMS的分解、自由基的产量以及电活化PMS降解三种酚类有机物（苯酚、双酚A和4-氯苯酚）的性能。

专利名称：一种动态动力学拆分合成光学纯的2-取代吲哚啉类化合物的方法
专利类型：发明专利
发明人：周少林,石维敏
申请号：CN201910793261.6
申请日：20190827
公开号：CN110437123A
公开日：
20191112
专利内容由知识产权出版社提供
摘要：本发明属于纯手性化合物的拆分制备技术领域，特别涉及一种动态动力学拆分合成光学纯的2‑取代吲哚啉类化合物的方法，其是以2‑取代吲哚啉原料和烯丙基‑3‑甲氧基苯基碳酸酯为原料，在消旋化组合物和脂肪酶的作用下，通过化学酶法协同动态动力学拆分得到具有一定光学纯度的2‑取代吲哚啉类化合物，具有较高的收率，能够减少反应原料用量，实现克级规模的制备得到光学纯的2‑取代吲哚啉类化合物，具有资源节省、经济高效等特点。

申请人：华中师范大学
地址：430079湖北省武汉市洪山区珞喻路152号
国籍：CN
代理机构：杭州宇信知识产权代理事务所(普通合伙)
代理人：张宇娟
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