SPG膜乳化与界面聚合法制备单分散多孔微囊膜

小粒径单分散中空储库结构微囊膜的制备具有重要学术意义和实用价值。为此采用了SPG(Shirasu-Porous-Glass)膜乳化法和界面聚合法，对小粒径单分散多孔微囊膜的制备进行了较系统的实验研究，以期为进一步制备多孔内接枝环境感应型功能凝胶开关的小粒径单分散微囊型靶向式药物载体提供基体。研究结果表明，采用SPG膜乳化法可制得单分散性良好的乳液液滴，进而采用界面聚合法可得到单分散微囊。用膜乳化方法易于控制乳液液滴及微囊的大小，在研究中SPG膜乳化法制备的乳液液滴及微囊的平均粒径大约是所用膜孔径的3．6倍。微囊膜的多孔性可以靠改变溶剂和单体的成分来进行控制，扫描电镜检测结果表明所制备出的不同粒径级别的单分散微囊膜均具有良好的多孔结构。     

膜乳化和微流控法制备单分散W／O乳液的研究

以油相为连续相、水相为分散相,分别采用SPG膜乳化法和微流控技术制备出了单分散W／O乳液。对两种制备单分散乳液的方法进行了系统比较。结果表明,微流控技术不仅更易操作,而且制备出的W／O乳液单分散性更好。     

二次膜射流乳化法制备单分散乳状液研究

为解决传统膜乳化法制备单分散O/W型乳状液中存在的粒径和通量的矛盾,介绍了采用二级陶瓷膜乳化在射流条件下制备单分散O/W乳状液的方法。2套一体式陶瓷膜乳化装置被串联使用,一级膜乳化采用孔径为0.16μm的ZrO2陶瓷膜,二级膜乳化采用孔径为1.5μm的-αA l2O3陶瓷膜。以甲苯/水体系为研究对象,阴离子表面活性剂(SDS)和非离子表面活性剂(乳化剂OP)分别被用作乳化剂。2种情况下均可获得单分散的乳液,能耗分别是1.53×105J/m3和1.21×105J/m3。因此,该方法可在较低的能耗下制备单分散乳液。     

陶瓷膜射流法制备单分散异辛烷/甲酰胺乳液的研究

乳液模板法是制备高度有序多孔材料的重要方法之一.采用二次陶瓷膜乳化在射流条件下制备单分散乳液的方法成功制备出一种非水乳液模板.一次射流过程采用平均孔径为0.2 μm的ZrO2陶瓷膜作为乳化介质,二次射流乳化过程采用平均孔径为1.6 μm的α-Al2O3陶瓷膜作为乳化介质.异辛烷/甲酰胺体系为研究对象,三嵌段高分子聚(乙二醇)-聚(丙二醇)-聚(乙二醇)作为乳化剂,制备出平均粒径在1～2 μm的单分散乳液模板,并考察了操作压力、异辛烷浓度对液滴粒径及粘度的影响.     

单分散油包水乳液制备的研究进展

单分散油包水(W/O)乳液在食品、化妆品、药剂以及高分子微球微囊合成等方面具有广泛的应用。该文综述了近年来单分散W/O乳液的主要制备方法及其基本原理,此外还简要介绍了其在单分散温敏性微球微囊和可生物降解微球微囊合成方面的应用,以期为单分散W/O乳液的制备提供参考。     

二次膜射流乳化法制备单分散乳液模板的研究

乳液模板法是一种制备高度有序多孔材料的重要方法,而膜乳化法则是一种新型的通过膜结构制备乳液的方法。文中提出了一种采用二次膜射流乳化制备单分散乳液模板的方法,平均孔径为0.16μm和1.5μm的陶瓷膜分别被作为两次乳化的乳化介质。采用异辛烷/甲酰胺体系为研究对象,嵌段高分子聚(乙二醇)聚(丙二醇)聚(乙二醇)作为乳化剂。实验表明一级膜乳化过程的通量为75.4 L/(m2.h),二级膜乳化过程的通量可达到169.9 L/(m2.h)。所得单分散乳液模板的平均粒径为1.8μm,且在10 h内能保持较好的稳定性。     

微流控法以单乳为模板制备单分散中空微囊的研究

单分散中空微囊在化工、医药、生物技术等领域有着广阔的应用前景。本文采用微流控技术制备了含甲基丙烯酸β羟乙酯和甲基丙烯酸甲酯两种单体的单分散水包油（O／W）乳液,并以此为模板,在致孔剂的作用下,光引发聚合成功制备了单分散聚甲基丙烯酸β羟乙酯-甲基丙烯酸甲酯的中空微囊。用光学显微镜和扫描电子显微镜对微囊进行系统的表征,结果表明,微囊的粒径在40μm左右,尺寸分布较窄,具有良好的单分散性,微囊外表面光滑,内表面粗糙,囊壁较薄,为中空结构。本研究中提出的方法为单分散中空微囊的制备提供了一条新的途径。     

纳米Fe3O4稳定的Pickering型ASA乳液

利用纳米Fe₃O₄作为稳定剂和乳化剂来制备Pickering型ASA（alkenyl succinic anhydride） 施胶乳液,并研究了固体颗粒浓度、油水比、水分散相pH对乳液类型、稳定性、形态及施胶性能的影响。结果表明,纳米Fe₃O₄能够乳化制备均一稳定的Pickering型ASA乳液。乳液在室温下静置稳定,析出油相体积分数随固体颗粒用量的增加而增大,随油水比的增大而减小。油水比为2：1,水分散相浓度为0.1%（质量分数）时制备的ASA乳液稳定性最佳。固体颗粒部分吸附在油/水界面处,部分分散在分散相中,随分散相中固体颗粒浓度的增加,乳液稳定性变差。乳液静置分层之前,ASA发生部分水解。在放置1 h后用于纸页浆内施胶,随ASA乳液用量的增加,纸页表面接触角逐渐增大,且纸页表面粗糙度下降。在ASA的添加量为1.0%（质量分数）时,纸页表面接触角达到93.5°,纸页表面粗糙度为15.924 μm。     

原油乳状液稳定性与乳化剂关系研究

分析了油水两相之间的界面张力大小,通过乳化实验测出乳状液的黏度变化和稳定时间,再借助显微镜观察水滴分散程度,最后得出对于酯类和磺酸盐类等大多数乳化剂,疏水基单烷基链越长,在油相中与油相之间交错的程度就会越复杂,配制出的乳状液性能越好;若乳化剂的疏水基团中存在不饱和双键,在空间上限制了烷基碳链在油相中的三维伸展,形成的乳状液乳化效果越差;若乳化剂的疏水基团中存在与烷基主链相同的支链,由于氢键的存在严重限制了疏水基在油相中的分散吸附,同时由于界面膜之间也会产生有一定的角度,使得界面膜的排列紧密程度变弱,导致乳状液性能变差。     

陶瓷膜乳化法制备O/W乳状液

膜乳化法是获得高质量单分散稳定乳状液的一种简单有效方法,以氧化铝陶瓷微滤膜为乳化媒介,大豆油为分散相,含有乳化剂的去离子水为连续相,直接制备O/W乳液.比较了膜乳化法与机械搅拌法的乳化效果;考察了乳化剂浓度、膜两侧压差和磁力搅拌转速对乳化效果的影响.结果表明:乳化剂浓度2%、膜面压差0.12MPa、搅拌转速450r/min为最佳乳化条件.     

Hydrophobic Modification and Regeneration of Shirasu Porous Glass Membranes on Membrane Emulsification Performance

The effect of hydrophobic modification and regeneration of Shirasu porous glass (SPG) membranes was systematically investigated on the monodispersity of emulsions. The results showed that the hydrophobic modification and regeneration of SPG membranes had little influence on the monodispersity of emulsions, no matter how many modification and regeneration runs were operated. The emulsification runs affected the emulsification performance to a certain extent when hydrophobically‐modified SPG membranes were used for preparing water‐in‐oil (W/O) emulsions repeatedly. However, they almost did not affect the emulsification performance when regenerated hydrophilic SPG membranes were used for preparing oil‐in‐water (O/W) emulsions. The SPG membranes could be used repeatedly after hydrophobic modification or regeneration with almost the same emulsification performance as fresh or freshly‐modified ones. The results provided some valuable guidance for the repetitive use of SPG membranes to prepare monodisperse O/W and W/O emulsions.     

Preparation of monodisperse water-in-oil-in-water emulsions using microfluidization and straight-through microchannel emulsification

Water-in-soybean oil-in-water (W/O/W) emulsions with an internal water phase content of 10–30% (vol/vol) were prepared by a two-step emulsification method using microfluidization and straight-through microchannel (MC) emulsification. A straight-through MC is a silicon array of micrometer-sized through-holes running through the plate. Microfluidization produced water-in-oil (W/O) emulsions with submicron water droplets of 0.15–0.26 μm in average diameter (d _av,w/o) and 42–53% in CV (CV_w/o) using tetraglycerin monolaurate condensed ricinoleic acid esters (TGCR) and polyglycerin polycondensed ricinoleic acid esters (PGPR) as surfactants dissolved in the oil phase. The d _av,w/o and viscosity of the W/O emulsions increased with an increase in internal water phase content. Straight-through MC emulsification was performed using the W/O emulsions as the to-be-dispersed phase and polyoxyethylene (20) sorbitan monooleate (Tween^® 80) as a surfactant dissolved in the external water phase. Monodisperse W/O/W emulsions with d _av,w/o/w of 39.0–41.0 μm and CV_w/o/w below 5% were successfully formed from a straight-through MC with an oblong section (42.8×13.3 μm), using the TGCR-containing systems. The d _av,w/o/w of the monodisperse W/O/W emulsions decreased as the internal water phase content increased because of the increase in viscosity of the to-be-dispersed phase. Little leakage of the internal water droplets and no droplet coalescence or droplet break-down were observed during straight-through MC emulsification.     

Mechanism of suspension polymerization of uniform monomer droplets prepared by glass membrane (Shirasu Porous Glass) emulsification technique

The mechanism of the unique suspension polymerization of uniform monomer droplets, without coalescence and breakup during the polymerization, was investigated using styrene (S) as a monomer mixed with water‐insoluble hexadecane (HD). The glass membrane (Shirasu Porous Glass, SPG) emulsification technique was employed for the preparation of uniform droplets. Depending on the pore sizes of the SPG membranes (1.0, 1.4, and 2.9 μm), polymer particles of an average diameter ranging from 5.6 to 20.9 μm were obtained with the coefficient of variation (CV) being close to 10%. The role of HD was to prevent the degradation of the droplets by the molecular diffusion process. Sodium nitrite was added in the aqueous phase to kill the radicals desorbed from the droplets (polymer particles), thereby suppressing the secondary nucleation of smaller particles. Each droplet behaved as an isolated locus of polymerization. With the presence of HD, the initial polymerization rate was proportional to 0.24th power of the benzoil peroxide (BPO) concentration. This peculiar behavior as compared with the ordinary suspension polymerization was explained by introducing the assumption that each droplet was composed of isolated compartments (cells) in which active polymeric radicals were dissolved in an S‐rich phase and surrounded by a rather incompatible S/HD (continuous) phase. The average number of radicals in the droplet increased initially due to the separate existence of polymeric radicals in compartments. As the polymerization progressed, the HD‐rich phase gradually separated, eventually forming macrodomains, which were visible by an optical microscope. The phase separation allowed polystyrene chains to dissolve in a more favorable S phase, and the homogeneous bulk polymerization kinetics took over, resulting in a gradual decrease of the average number of radicals in the droplet until the increase of viscosity induced the gel effect. When no HD was present in the droplets, the polymerization proceeded in accordance with the bulk mechanism except for the initial retardation by the entry of inhibiting radicals generated from sodium nitrite in the aqueous phase. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1025–1043, 2000     

聚(N-异丙基丙烯酰胺)温敏微球的粒径及单分散性

Thermo-responsive poly (N-isopropylacrylamide-co-styrene ) [P(NIPAM-co-St)] hydrogel microspheres were prepared by surfactant-free emulsion polymerization. The effects of initiator dosage, stirring rate, phase ratio and polymerization time on particle size and monodispersity were investigated. The results showed that, with increasing initiator dosage, mean diameter increased slightly to a maximum, and then decreased drastically; meanwhile, the monodispersity of the particles became a little better at first, and then became worse significantly. With increasing stirring rate, particle diameter decreased while the monodispersity became worse. When the amount of phase rate increased, the mean diameter became larger simply, whereas the monodispersity became worse firstly and then became better again. As the polymerization proceeded, the mean diameter of the particles hardly changed, and the monodispersity became better gradually. The microspheres prepared under the optimum experimental conditions showed satisfactory particle size and monodispersity.     

The membrane emulsification process—a review

Membrane emulsification has received increasing attention over the last 10 years, with potential applications in many fields. In the membrane emulsification process, a liquid phase is pressed through the membrane pores to form droplets at the permeate side of a membrane; the droplets are then carried away by a continuous phase flowing across the membrane surface. Under specific conditions, monodispersed emulsions can be produced using this technique. The purpose of the present paper is to provide a review on the membrane emulsification process including: principles of membrane emulsification, influence of process parameters and industrial applications. Small‐scale applications such as drug delivery systems, food emulsions, and the production of monodispersed microspheres are also included. Compared with conventional techniques for emulsification, membrane processes offer advantages such as control of average droplet diameter by average membrane pore size and lower energy input. Copyright © 2004 Society of Chemical Industry     

Stirred tank membrane emulsification using flat metallic membranes: A dimensional analysis

The performance of a membrane emulsification unit, using flat membranes in a stirred tank, has been examined by dimensional analysis. The dimensionless numbers were defined in terms of shear and membrane pore size. Dimensionless droplet size prediction models based on simple force balances were used to select the most representative dimensionless numbers including operating parameters. Oil-in-water emulsions were produced with tailor-made metallic membranes with pore sizes of 30 and 50 μm. Results showed that monodisperse emulsions were produced with span values around 0.5, significantly lower than when a rotor-stator homogenizer is used. The influence of the selected operating parameters (impeller rotational speed, continuous phase viscosity and dispersed phase flux) on droplet size distribution was studied and experimental results were compared with droplet size prediction models. Impeller rotational speed and membrane pore size were the key parameters influencing emulsion droplet size and monodispersity. A correlation based on the Euler dimensionless number, including all the operating parameters is proposed.     

Emulsification using tubular metallic membranes

Tubular metallic membranes with pore diameters of 5 and 10 μm have been used in a cross-flow unit to prepare monodisperse oil-in-water emulsions (O/W) with span values as low as 0.67, significantly lower than for emulsions prepared with a rotor–stator homogenizer. The influence of typical operating parameters (continuous phase flow rate and transmembrane pressure) on droplet size distribution was studied. The smallest droplets were obtained at low transmembrane pressures and high continuous phase flow rates. The droplet production with tubular metallic membranes was higher than with other types of tubular membranes, such as SPG or ceramic.Experimental results were compared with those obtained in a stirred tank unit operating under similar conditions and using flat metallic membranes with the same pore diameter. Droplet size prediction models based on simple force balances were applied to compare theoretical and experimental droplet diameters. The droplet formation regime (dripping, jetting) was also studied for both types of membranes.