High‐Internal‐Phase Pickering Emulsions Stabilized Solely by Peanut‐Protein‐Isolate Microgel Particles with Multiple Potential Applications

High‐internal‐phase Pickering emulsions have various applications in materials science. However, the biocompatibility and biodegradability of inorganic or synthetic stabilizers limit their applications. Herein, we describe high‐internal‐phase Pickering emulsions with 87 % edible oil or 88 % n‐hexane in water stabilized by peanut‐protein‐isolate microgel particles. These dispersed phase fractions are the highest in all known food‐grade Pickering emulsions. The protein‐based microgel particles are in different aggregate states depending on the pH value. The emulsions can be utilized for multiple potential applications simply by changing the internal‐phase composition. A substitute for partially hydrogenated vegetable oils is obtained when the internal phase is an edible oil. If the internal phase is n‐hexane, the emulsion can be used as a template to produce porous materials, which are advantageous for tissue engineering.     

表面活性剂稳定高内相乳液的研究进展

具有较高孔隙率和较高比表面积的多孔聚合物材料在能源、化工、生物和功能性材料等领域应用广泛。目前越来越多的研究是以高内相乳液为模板来制备多孔聚合物材料,其中高内相乳液的稳定对多孔聚合物材料的制备十分重要。本文主要介绍了近年来发展的多种用于高内相乳液滴稳定的表面活性剂,以及以高内相乳液为模板制备得到的多孔聚合物材料在多个领域中的应用。     

Composition Ripening in Mixed Water-in-Oil Emulsions Stabilized with Solid Particles

Water and oil transport in emulsified systems is far from being elucidated. Calorimetric analysis has proved to be an appropriate technique to study composition ripening in mixed water in oil emulsions. In this article, the role of the stabilizing agent is studied and particular attention is given to emulsions stabilized solely with solid particles. Mixed emulsions are prepared by mixing two simple water-in-oil (W/O) emulsions, one with pure water droplets and one with droplets containing an aqueous urea solution. At different time intervals, a sample is introduced in a calorimeter cell and submitted to successive cooling and heating cycles. During the cooling phase, the aqueous internal phase solidifies at a temperature which depends on its composition. Just after the mixed emulsion was prepared, the calorimetric experiment identified two solidification peaks, one corresponding to pure water droplets, and the other one to urea solutions. After a long enough stabilization time, just one peak was observed, showing that the systems evolved toward one type of droplets characterized by a unique composition, due to water transfer between the two aqueous phases. The effect of emulsion stabilizing agent (particles or nonionic emulsifier) on the kinetics of water transfer was investigated.     

Van der Waals Emulsions: Emulsions Stabilized by Surface‐Inactive,Hydrophilic Particles via van der Waals Attraction

Surface‐inactive, highly hydrophilic particles are utilized to effectively and reversibly stabilize oil‐in‐water emulsions. This is a result of attractive van der Waals forces between particles and oil droplets in water, which are sufficient to trap the particles in close proximity to oil–water interfaces when repulsive forces between particles and oil droplets are suppressed. The emulsifying efficiency of the highly hydrophilic particles is determined by van der Waals attraction between particle monolayer shells and oil droplets enclosed therein and is inversely proportional to the particle size, while their stabilizing efficiency is determined by van der Waals attraction between single particles and oil droplets, which is proportional to the particle size. This differentiation in mechanism between emulsification and stabilization will significantly advance our knowledge of emulsions, thus enabling better control and design of emulsion‐based technologies in practice.     

Osmotically Driven Formation of Double Emulsions Stabilized by Amphiphilic Block Copolymers

Double emulsions are valuable for the formation of multi‐compartmental structures. A variety of pathways to prepare double emulsions have been developed, but high‐throughput routes to droplets of controlled size and architecture remain scarce. A new single‐step process is introduced for preparation of water‐in‐oil‐in‐water double emulsions by a previously unexplained process of self‐emulsification. We show that the origin of this process is the osmotic stress resulting from the presence of salt impurities within the amphiphilic block copolymers used for emulsion stabilization. Further, we utilize osmotically driven emulsification to tailor the structures of multiple emulsions, which upon solvent evaporation can yield multi‐compartmental capsules or hierarchically structured porous films.     

疏水缔合聚合物稳定乳状液的研究*

本文综述了近年来疏水缔合聚合物稳定乳状液的研究进展。论述了疏水缔合聚合物水溶液的性质,由于其较复杂的分子结构以及其分子主链上疏水基团的缔合作用,使其水溶液增稠的能力比小分子表面活性剂的增稠能力强的多。另外,对疏水缔合聚合物单独稳定乳状液的研究现状进行了介绍,其稳定乳状液的机理与小分子表面活性剂不同。同时讨论了疏水缔合聚合物与表面活性剂的相互作用,此类聚合物可与小分子表面活性剂通过静电和疏水缔合发生强烈的相互作用形成复合体系,并评述了其复配体系稳定乳状液的情况。最后总结了疏水缔合聚合物稳定乳状液的机理。     

Three-Component Olive Oil-In-Water High Internal Phase Emulsions Stabilized by Palm Surfactant and Their Moisturizing Properties

In the present study, olive oil was used for the preparation of three-component high internal phase emulsions with oil volume fraction of more than 0.77 stabilized by palm-based polyoxyethylene lauryl ether for the first time. These emulsions were investigated on their morphology, structural properties, stability, and hydration efficacy. Droplet size distribution observed from the optical micrographs was in agreement with the light scattering results, which suggested that droplet size was influenced by oil phase and surfactant concentrations. Rheological results exhibiting flow curves cross-over implied structural build-up that gave rise to high stability which was supported by stable three-month storage at an elevated temperature. The hydration efficacy of the emulsion was examined in vivo using a corneometer.     

Surfactant-Free Multiple Pickering Emulsions Stabilized by Combining Hydrophobic and Hydrophilic Nanoparticles

A series of W/O/W or O/W/O emulsion stabilized solely by two different types of solid nanoparticles were prepared by a two-step method. We explored the option of particular emulsifiers for the multiple Pickering emulsions, and a variety of nanoparticles (silica, iron oxide, and clay) only differing in their wettability was used. The primary W/O emulsion was obtained by the hydrophobic nanoparticles, and then the hydrophilic nanoparticles were used as emulsifier in the secondary emulsification to prepare the W/O/W emulsion. In a similar way, the primary O/W emulsion of the O/W/O emulsion was stabilized by the hydrophilic nanoparticles, while the secondary emulsification to prepare the O/W/O emulsion was effected with the hydrophobic nanoparticles. The resultant multiple Pickering emulsion was stable to coalescence for more than 3 months, except the W/O/W emulsions of which the secondary emulsion stabilized by clay nanoparticles became a simple O/W emulsion in a day after preparation. Moreover, the temperature and pH sensitive poly(N-isopropylacrylamide-co-methacrylic acid) (P(NIPAm-co-MAA)) microgels were introduced as an emulsifier for the secondary emulsification to obtain the stimulus-responsive multiple W/O/W emulsion. Such microgel-stabilized multiple emulsions could realize the efficient controlled release of water-soluble dye, Rhodamine B (RB) on demand in a multiple-emulsion delivery system.      

Pickering Emulsions Stabilized with Curcumin-Based Solid Dispersion Particles as Mayonnaise-like Food Sauce Alternatives

Pickering emulsions, which are emulsions stabilized by colloidal particles, are being increasingly positioned as novel strategies to develop innovative food product solutions. In this context, the present work aims to develop Pickering emulsions stabilized by natural-based curcumin-loaded particles produced by the solid dispersion technique as promising mayonnaise-like food sauce alternatives. Two particle formulations (KC1 and KC2) were produced using k-carrageenan as the matrix material and different curcumin contents, then employed in the preparation of three Pickering emulsion formulations comprising different oil fractions (φ) and particle concentrations (KC1 φ 0.4 (4.7%), KC2 φ 0.4 (4.7%) and KC2 φ 0.6 (4.0%)). The creaming index tests accompanied by the optical microscopy analysis evidenced the good stability of the developed products for the tested period of 28 days. The final products were tested concerning color attributes, pH, oxidative stability, textural, and nutritional composition, and compared with two commercial mayonnaises (traditional and light products). Overall, the produced emulsions were characterized by a bright yellow color (an appealing attribute for consumers), an acidic pH (similar to mayonnaise), and a considerably improved oxidative stability, implying a foreseeable longer shelf life. The sauce KC1 φ 0.4 (4.7%) showed a similar texture to the light commercial mayonnaise, being a promising alternative to conventional sauces, holding a low-fat content and potentially added benefits due to the curcumin and virgin olive oil intrinsic properties.     

Water-in-Oil Emulsions Stabilized by Asphaltenes Obtained from Venezuelan Crude Oils

W/O emulsions were studied using asphaltenes as surfactants. Asphaltenes were obtained from three Venezuelan crude oils: “Lago Cinco,” “Rosa Mediano,” and “Ayacucho.” They were extracted using n-heptane as a precipitanting agent. The following variables were studied: concentration of asphaltenes in the oleic phase and pH of the aqueous phase. An increase in asphaltene concentration in the oleic phase increases emulsion stability. On the other hand, the most stable emulsions correspond to an alkaline aqueous phase. Likewise, emulsion stability was higher for asphaltenes obtained from “Lago Cinco” crude oil and lowest from Rosa Mediano asphaltenes.     

Study by Differential Scanning Calorimetry of Water-in-Oil Emulsions Stabilized by Clays and CTAB

In this work, we have tested various formulations in order to get emulsions containing pure water, Tunisian olive oil, Tunisian clays, and an ammonium salt. Two different types of clays: smectite and kaolinite and the cethyltrimethylamonium bromide (CTAB) were tested. CTAB is used as surfactant and a compound modifying the clays properties. The amount of CTAB being fixed at 0.66 w/w, the proportions of clays were varied from 0 to 9% for each of the following proportions of water: 10, 20, 30%. To the aqueous phase obtained by mixing two separate aqueous phases: water + CTAB and water + clay, the oil was added drop by drop, the agitation being maintained at 5000 rpm. The obtained mixtures were analyzed by Differential Scanning Calorimetry (DSC), optical microscopy and bottle tests. An optimized formulation containing water (30%), smectite clay (5.3%) and CTAB (0.66%) was found to give W/O emulsions which kinetic stability is greater than 75 days regarding coalescence and greater than 700 hours regarding sedimentation.     

高内相比乳液模板法合成多孔材料的研究进展

综述了以高内相比乳液作模板制备多孔材料的研究进展,介绍了油包水(W/O)乳液体系法、水包油(O/W)乳液体系法和超临界CO2法等制备方法、各种多孔材料的泡孔及通道直径、比表面积、密度等性能,以及这类多孔材料在生物医学、有机化学品清除、化学催化、水溶液中固体杂质分离、液相色谱、电化学传感器等领域的应用,并对其发展前景进行了展望。     

Double Emulsions Stabilized by Xanthan in the Absence of Hydrophilic Surfactant

The preparation of double water-in-oil-in-water (W/O/W) emulsions containing xanthan gum (XG) in the absence of hydrophilic surfactant was investigated. The emulsions were prepared by the two-step emulsification process. The stability of these systems was evaluated through the evaluation of physicochemical and rheological properties. Microscopic observations in combination with particle size analysis were also performed. The obtained results show that it is possible to prepare stable double emulsions with a single polysaccharide by using the indirect process. The stability depends on the viscosity of the continuous phase and hence the concentration of XG. The apparent viscosity of the emulsions increased with the increase of XG concentration. Particle size analysis shows that the droplet sizes are directly related to XG concentration.     

硅氧烷乳液聚合过程中大颗粒形成机理研究Ⅰ．阳离子型乳液的耐电解质稳定性

探讨了二甲基聚硅氧烷阳离子型乳液耐电解质稳定性的影响因素。结果表明,加入少量的非离子型表面活性剂与阳离子型乳化剂并用进行乳液聚合,可以保护乳液粒子,防止由于电解质引起的乳液粒子的相互凝聚而形成大颗粒。     

硅氧烷乳液聚合过程中大颗粒形成机理研究：Ⅰ.阳离子型乳液的耐电解质…

探讨了二甲基聚硅氧烷阳离子型乳液耐电解质稳定性的影响因素。结果表明，加入少量的非离子型表面活性剂与阳离子型乳化剂并用进行乳液聚合，可以保护乳液粒子，防止由于电解质引的乳液粒子的相互凝聚而形成大颗粒。     

马来松香酸和纳米氧化铝颗粒协同稳定具有pH响应性的Pickering 乳液

使用有机颗粒稳定Pickering乳液受到越来越多的关注, 润湿性可调的有机颗粒且结合纳米无机颗粒协同稳定不同类型的Pickering乳液却鲜有报道. 系统研究了基于具有多羧酸基团的松香基衍生物马来松香(MPA)与纳米Al₂O₃颗粒在不同pH条件下形成的乳液类型及相关机理. 研究发现, 在单一MPA颗粒体系条件下, pH可以诱导乳液的类型由W/O Pickering乳液到O/W Pickering乳液, 到最后O/W乳液的转变, MPA的亲水性随着pH升高而增强是该乳液转变的原因. 当纳米Al₂O₃颗粒加入到MPA中后, 吸附在MPA颗粒上的亲水性Al₂O₃导致MPA颗粒亲水性增加, 从而可以使W/O Pickering乳液转变为O/W Pickering乳液(pH=1). 当pH=6时, MPA分子与纳米Al₂O₃颗粒同时具有较强的亲水性且分别无法形成稳定的乳液, 但两者的混合体系可以形成稳定的W/O Pickering乳液, 这是因为MPA分子与纳米Al₂O₃颗粒可以在水溶液中形成疏水性较强的络合物. 另外, 研究了MPA浓度及油相体积分数对乳液外观及粒径的影响, 发现随着MPA浓度增加Pickering乳液的粒径逐渐减小, 增加油相的体积分数会引起粒径的增大. 最后, 利用Zeta电势、颗粒在油水界面吸附率、接触角及表/界面张力研究了稳定Pickering乳液的稳定机理, 在油水界面上吸附的类似盔甲状颗粒层及颗粒层之间形成的网状结构是乳液液滴保持稳定的原因. 为Pickering乳液的绿色化制备提供了一种新的途径, 将在化妆品、医药及新材料等领域得到重要应用.