微孔分散法制备单分散微胶囊研究进展

小粒径单分散多孔微胶囊的制备具有重要学术意义和实际应用价值。本文在介绍传统的微胶囊合成方法和特性表征的基础上,重点阐述利用孔径均一的SPG膜分散乳化法,以及微通道法制备粒径单分散微乳液和微胶囊的工艺过程、技术原理及该技术的开发应用现状。     

单分散聚苯乙烯微球的制备及表征

应用膜乳化-液中干燥法成功制备出粒径为2～20μm的单分散聚苯乙烯(PS)微球.PS微球的粒径主要由膜孔径决定,其值约为膜孔径的2倍;PS溶液的浓度对其也有一定的影响.膜乳化过程中的压力对微球粒径的分散性有很大的影响,在一定压力范围内,粒径呈单分散.在分散相中加入致孔剂,制备出表面多孔的PS微球.采用复乳-液中干燥法制备出中空PS微球.     

用混合乳化剂制备不同粒径的乳状液

乳状液按其颗粒大小可分为普通乳状液（约IN10pm，微小乳状液（01～0·4Pm），微乳状液（001卜0．lPm）．其中微小乳状液比普通乳状液颗粒小，分散均匀，稳定性好，比微乳状液所需乳化剂的用量要低得多，在实际应用中很有前景．但有关微小乳状液的研究工作做得很少［’－‘］．在乳化过程中，若不需外界做功，靠乳化剂的自身作用，使两种不相混溶的液体自动混合，生成乳状液称为自发乳化，无需专门的乳化设备即可方便地制备出乳状液．目前自发乳化所得的乳状液颗粒都较大，稳定性较差卜一＼若将微JJ、乳状液的制备与其自发形成的条件结合…     

Pickering多重乳状液的一步法合成及形成机理研究

使用锂皂石层状纳米颗粒与表面活性剂(Span80)复配制备乳状液的过程中, 在乳化之前对锂皂石颗粒水分散体系进行稀释, 则可以通过一步法制备出性能稳定的W/O/W型Pickering多重乳状液. 研究了Span80浓度、锂皂石浓度以及稀释用水的量对生成乳状液的类型及稳定性的影响规律, 对一步法合成Pickering多重乳状液的成因及机理进行了探讨和分析. 实验结果表明, 对锂皂石颗粒水分散体系的稀释是一步法合成稳定Pickering多重乳状液的关键因素, 稀释用水的量决定了多重乳状液中的内水相体积. 随着Span80浓度的增加, 多重乳状液的粒径减小, 稳定性迅速增加. 锂皂石颗粒的浓度能够影响乳状液的类型, 但对乳状液的稳定性以及乳状液的粒径影响不大. 锂皂石颗粒在水分散体系中缓慢的扩散速率是一步法合成Pickering多重乳状液的主要原因.     

含VE微胶囊的制备及其控制释放性能研究

以天然维生素E（VE）为芯材，利用Shirasu porous glass (SPG) 膜乳化结合液中干燥法，制备了粒径单分散的聚苯乙烯（PS）微胶囊.微胶囊的粒径为膜孔径的4倍，粒径单分散系数CV小于0.2.考察了改变PS和VE的比例及微胶囊的粒径对控制释放性能的影响.     

非离子表面活性剂体系的液晶与自发乳化(I)

乳状液广泛用干工、农业、医药、食品与化妆品生产中．近年来，许多研究集中在如何制备颗粒细小、均匀的乳状液方面．用通常的机械法制备细小乳状液，需要较昂贵的设备和消耗较多能量，其颗粒分布仍不够均匀．近来，一些研究发现，有可能采用物理化学方法，而不需乳化机械，只要选用合适的乳化剂，在轻微的搅拌下，可制得颗粒细小而均匀的微小乳状液[1，2]．我们在采用反相乳化法和自发形成O／W型微小乳状液的研究中发现，在自发乳化的中间过程中常有液晶棺和粘稠的胶状物形成[3，4]．有关液晶对乳状液的稳定作用前人有过较多研究[5]，但在…     

乳状液-中空纤维膜萃取钕及其传质性能研究

采用非分散的萃取方式,将乳状液膜体系Span80/皂化D2EHPA/煤油/液体石蜡/盐酸通过中空纤维膜对钕进行了逆流萃取,研究了乳化剂浓度、乳状液与水相流量比、内相盐酸浓度、萃取时间等因素对萃取率的影响。结果表明,乳状液和水相流量越小、乳状液内相盐酸浓度越大,萃取率越高,内相富集倍数越大。将乳液循环萃取70次后,内相富集倍数达50.2,表明乳状液在中空纤维膜萃取器中对稀土有很好的萃取和富集效果。与乳状液膜的分散萃取方式相比,非分散萃取方式的萃取速率更快,而且萃余水相澄清,液膜稳定性好,泄漏少,膜溶胀小。同时还计算了非分散萃取过程基于水相的总传质系数实验值和理论值,当调节参数Kf(络合反应传质系数)的取值为3.5×10-9m.s-1,水相流量大于10×10-6m3.s-1时,实验值与理论预测值相吻合。     

功能化磁性纳米粒子在乳状液制备及破乳中的应用及作用机制

功能化磁性纳米粒子因其独特的理化性质,在乳状液制备与破乳领域的应用受到广泛关注。本文归纳了功能化磁性纳米粒子的制备方法、合成结构与特征性质,阐述了其在乳状液制备及破乳中的应用过程,重点分析了磁性纳米粒子在溶液中良好分散、稳定吸附于油水界面排布为膜结构的作用行为,尤其是磁性纳米粒子的磁响应特征对乳状液中界面性质、液滴形貌及运动状态的影响,并进一步总结出其表面性质及作用行为对稳定乳状液或使乳状液破乳的规律。针对磁性纳米粒子对乳状液稳定性影响规律的探究可为其在应用领域提供理论支持。最后本文就功能化磁性纳米粒子研究中亟待解决的新问题作出展望。     

白油乳状液稳定性实验研究与机理分析

乳状液的微观特征影响着油包水乳状液的稳定性，从而影响油基钻井液的稳定性能。室内选用3^#白油、26%CaCl₂水溶液、JH主辅乳化剂，采用超声分散乳化方法，配制得到油包水型白油乳状液。采用显微图像技术，研究了JH主辅乳化剂加量、油水比、有机土对白油乳状液微观特性的影响；以油水界面张力、动态界面张力以及界面扩张粘弹性等为参数分析了乳状液稳定性的机理。结果表明：JH主辅乳化剂配比为4∶1,加量为4%,油水比为80∶20时，白油乳状液中的分散相呈球形液珠，直径为3.31～12.93μm;油水界面张力为0.559 mN·m^-1;JH主辅乳化剂形成的油水界面膜强度大，白油乳状液稳定性好；有机土与JH主辅乳化剂的协同作用使白油乳状液和油基钻井液的稳定性能显著提高。     

无皂相反转乳化法制备高分子水基分散体系

高分子树脂水基分散体系是指高分子树脂以微粒形式分散于水中 ,包括高分子乳液、高分子悬浮液等体系 .由于高分子树脂水基分散体系具有低成本 ,高性能 ,无污染等优点 ,一直受到普遍关注 .高分子树脂乳液一般通过乳液聚合制备 .该方法只适用于由含双键的单体制备的加聚产物 .而在制备缩聚产物的乳液时 ,乳液聚合方法局限性很大 ,而最近发展起来的相反转乳化技术 ,适用于制备包括加聚产物和缩聚产物在内的大多数高分子水基分散体系 ,拓宽了高聚物水基分散体系的范围 [1] .杨振忠等 [2～ 5] 利用相反转乳化技术制备了未固化和可固化的环氧树脂…     

Preparation characteristics of water-in-oil-in-water multiple emulsions using microchannel emulsification

Microchannel (MC) emulsification is a novel technique for preparing monodispersed emulsions. This study demonstrates preparing water-in-oil-in-water (W/O/W) emulsions using MC emulsification. The W/O/W emulsions were prepared by a two-step emulsification process employing MC emulsification as the second step. We investigated the behavior of internal water droplets penetrating the MCs. Using decane, ethyl oleate, and medium-chain triglyceride (MCT) as oil phases, we observed successful MC emulsification and prepared monodispersed oil droplets that contained small water droplets. MC emulsification was possible using triolein as the oil phase, but polydispersed oil droplets were formed from some of the channels. No leakage of the internal water phase was observed during the MC emulsification process. The internal water droplets penetrated the MC without disruption, even though the internal water droplets were larger than the resulting W/O/W emulsion droplets. The W/O/W emulsion entrapment yield was measured fluorometrically and found to be 91%. The mild action of droplet formation based on spontaneous transformation led to a high entrapment yield during MC emulsification.     

Effect of interfacial tension on the dynamic behavior of droplet formation during microchannel emulsification

Microchannel (MC) emulsification is a novel technique for producing monodisperse emulsions. In this study, we investigated the effect of interfacial tension on the dynamic behavior of droplet formation with various surfactant concentrations. Interfacial tension did not affect the resultant droplet diameter in lower flow velocity ranges, but it did affect the time-scale parameters. These results were interpreted using the droplet formation mechanism reported in our previous study. At surfactant concentrations below 0.3%, the emulsification behavior was differed from that at higher surfactant concentrations. An analysis of diffusional transfer indicated that dynamic interfacial tension affects the emulsification behavior at lower surfactant concentrations. Dynamic interfacial tension that exceeded the equilibrium value led to a shorter detachment time. This resulted in stable droplet formation of monodispersed emulsions by spontaneous transformation, even at flow velocities above the predicted critical flow velocity. A previous study predicted that the droplet formation would become unstable and polydispersed larger droplets would form over critical flow velocity. Wetting of the MC with the dispersed phase at lower surfactant concentrations induced formation of larger polydispersed droplets at high flow velocities.     

Supramolecular Polymer Emulsifiers for One-step Complex Emulsions

Complex emulsions,such as double emulsions and high-internal-phase emulsions,have shown great applications in the fields of drug delivery,sensing,catalysis,oil-water separation and self-healing materials.Their controllable preparation is at the forefront of interface and material science.Surfactants and polymers have been widely used as emulsifiers for building complex emulsions.Yet some inherent disadvantages exist including multi-step emulsifications and low production efficiency.Alternatively,supramolecular polymer emulsifier for complex emulsions via one-step emulsification is rising as a new strategy due to the ease of preparation.In this feature article,we review our recent progresses in using supramolecular polymer emulsifiers for the preparation of complex emulsions.Double emulsions and high-internal-phase emulsions are successfully prepared via one-step emulsification with the help of different supramolecular interactions including electrostatic,hydrogen bond,coordination interaction and dynamic covalent bond,which will be particularly emphasized in detail.In the end,a comprehensive prospect is given for the future development of this field.This article is expected to provide new inspirations for preparing complex emulsions via supramolecular routes.     

Production of Oil-in-Water Microspheres Using a Stainless Steel Microchannel

From the point of view of practical application of the microchannel (MC) emulsification technique, which can be used to produce super-monodispersed microspheres (MS), we fabricated a stainless steel MC and investigated the production and characterization of oil-in-water (O/W) MS using a stainless steel MC instead of a silicon MC plate. We discovered that a stainless steel MC could not be fabricated precisely at a 1-&mgr;m scale; because of its multicrystal property, it can only be processed mechanically on a 10-&mgr;m scale. O/W-MS ranging from 20 to 210 &mgr;m in average diameter were produced using a stainless steel MC with 10 to 80 &mgr;m in equivalent diameter. The MS produced were monodispersed with a coefficient of variation lower than 3% for each individual channel. This value is smaller than that of normal emulsions obtained by the conventional emulsification techniques by 1 order of magnitude. The average diameter of the MS produced at breakthrough pressure was about 2.6 times the stainless steel MC equivalent diameter. The operation pressure affects the MS formation, causing a size-stable zone, size-expanding zone, and outflow zone observed. Larger stainless steel MC demonstrated difficulties in stably producing monodispersed O/W-MS. The breakthrough pressure was approximately inversely proportional to the MC equivalent diameter. Copyright 2001 Academic Press.     

Highly concentrated (gel) emulsions,versatile reaction media

Highly concentrated (gel) emulsions are characterised by dispersed phase volume fractions exceeding 0.74, the critical value for the most compact packing of monodispersed undistorted spheres. Their structure consists of polyhedral droplets separated by thin films of continuous phase, a structure resembling gas–liquid foams. Their rheological properties vary from elastic to viscoelastic having a gel appearance. One of the most promising applications is their use as reaction media. The recent advances in the preparation of low-density polymeric materials (solid foams, aerogels) are reviewed and new applications are described. These include the preparation of dual meso/macroporous inorganic oxide materials and the use of gel emulsions as alternative to conventional solvent media in chemical and enzyme-catalysed reactions.     

Visualization and characterization of SPG membrane emulsification

Shirasu-porous-glass (SPG) membrane emulsification is highly attractive for various fields of foods, cosmetics, and pharmaceuticals because this technique produces monodispersed emulsions. However, there are few reports on the observation of membrane emulsification at the membrane surface. In the present work, we aimed to visualize the membrane emulsification using a microscope high-speed camera system. The direct observation made it possible to measure the mean rate of droplet formation and the percentage of active pores. The mean rate of droplet formation ranged 0.3–12 s⁻¹ and the percentage of active pores ranged 0.3–0.5% under the dispersed-phase flux of 0.58×10⁻⁶–5.8×10⁻⁶ m³/(m² s). We also observed that the droplets were formed without continuous-phase flow and the droplets were also formed by shear force at the continuous-phase flow under different experimental conditions. The balance among the dispersed-phase flux and the continuous-phase flow velocity influenced droplet formation.     

Regulating the Oil-Water Interface to Construct Double Emulsions: Current Understanding and Their Biomedical Applications

Double emulsions have been extensively used in scientific researches and industrial applications due to their attractive unique feature of multiple phases. However, constructing droplets with such a complex structure is not a simple task for all time. The simultaneous existence of two contradictory interfaces makes it hard to prepare stable double emulsions in principle and in practice. Over the past century, tremendous efforts have been devoted by myriads of scientists to make progresses in both theory and preparation of double emulsions. In this review, the current understanding of double emulsions is systematically revealed. In addition to emphasizing the corresponding pioneer and landmark works as many as possible, the state-of-the-art achievements will also be discussed. By regulating the oil-water interface with smartly designed interface-active agents in combination with varying the phase volume fractions, the basic theory framework based on the phase inversion from simple emulsions to double emulsions is also summarized. Technical preparation strategies of emulsification are introduced to show the building process of the two contradictory interfaces in one system. Furthermore, some specific biomedical applications of double emulsions are also discussed, which is expected to stimulate further innovation and utilization of double emulsions.     

Influence of a mixed ionic/nonionic surfactant system and the emulsification process on the properties of paraffin emulsions

Paraffin emulsions are important in technological applications such as coating in the food packaging industry or to provide waterproof properties to particleboard panels. Small particle size (about 1.0 μm) and low polydispersity are required to form stable paraffin emulsions for these applications. In this context, the main objective of the present work is to study the influence of the surfactant system and the emulsification process on the properties of paraffin emulsions. A high pressure homogenizer was used to prepare the emulsions and its characterization was made by means of optical microscopy, laser diffraction and electrophoretic mobility measurements. Emulsions were prepared as a function of the ionic/nonionic surfactant ratio, the total surfactant concentration and the homogenization pressure. A simple theoretical model to predict the minimum particle size was used, assuming that surfactant is either at the oil-water interface or as monomer in the external phase. Experimental and theoretical data are on good agreement and the formation of stable emulsions is explained according to such model. This result could be of prime importance in order to formulate new paraffin emulsions.     

柴油-生物质油乳化燃料最佳HLB值及理化性质研究

采用超声波乳化法制备柴油-生物质油乳化燃料,并研究了乳化燃料所需乳化剂的最佳亲水亲油平衡（HLB）值以及乳化条件对乳化燃料稳定性的影响,测定了乳化燃料的密度、黏度、闭口闪点、烟点、凝点和总热值等理化性质。结果表明,柴油-生物质油乳化燃料乳化剂的最佳HLB值为5.5~6.2;当乳化温度为50℃~60℃、单位容积输入功为180J/mL~300J/mL时,乳化燃料的稳定性最好;乳化燃料的密度、黏度、闪点和烟点随生物质油比例的增加而增大,而凝点和总热值则随生物质油比例的增加而降低。