A THEORY OF THE FORMATION OF MICROEMULSIONS

A mathematical model was proposed (1) in a recently published paper in an attempt to represent the formation of microemulsion systems. However, the model fits microemulsion systems only up to certain critical dispersed phase volume, known as the percolation threshold. A single total free energy minimum corresponding to a stable system was found by the model for phase volumes below the percolation threshold. If the dispersed phase volume is further increased, the model predicts instability with no free energy minimum. However, experimental results (1,2) indicate percolation of microdroplets above the percolation threshold before the system eventually breaks down upon further increase of the phase volume. An extra free energy term from the interaction between microdroplets is introduced and incorporated into the model. This new model now predicts two free energy minima above the percolation threshold of the dispersed phase corresponding to polydispersity of the system. Further increase in dispersed phase volume will then cause the system to become unstable.     

THE EFFECT OF ALCOHOLS WITH DIFFERENT STRUCTURES ON THE FORMATION OF WARM O/W MICROEMULSIONS

The influence of twenty five different alcohols on the formation of warm oil-in-water (O/W) microemulsions was investigated. Selected concentrations of each alcohol were added to fixed amounts of stearic acid, Tween 20 and water at 65 ° C. Fifteen alcohols formed microemulsions, at least at one of the concentrations. A pattern recognition study was performed to elucidate the activities of the alcohols by Principal Component Analysis (PCA). Linear Discriminant Analysis (LDA) was used to classify them. Two classification functions, obtained for alcohols forming / not forming microemulsions, suggest that the formation of warm O/W microemulsion is linked to the nature and the dimension/lipophilicity of the alcohol.     

THE EFFECT OF ALKANES ON THE FORMATION OF ULTRAFINE SILVER BROMIDE PARTICLES IN IONIC W/O MICROEMULSIONS

ABSTRACT

Ultrafine AgBr particles formed in w/o microemulsions with different chain length of alkanes were studied by UV-VIS spectrophotometry, stopped-flow spectrophotometry and transmission electron microscopy. The ultrafine particles of AgBr (5-7?nm in diameter) were obtained by mixing two separately prepared microemulsion systems both containing AOT, n-hexane and an aqueous solution of either AgNO³ or NaBr.The size distribution of the nearly spherical AgBr particles broadened from 5 to about 10?nm as chain length of alkane was increased from n-hexane to n-octane. When n-dodecane or a higher alkane was used, the microemulsion system became increasingly unstable causing precipitation of AgBr.     

BUTYL LACTATE: A USEFUL COSURFACTANT TO PREPARE O/W MICROEMULSIONS WITH SDS

The possibility of substitution of the conventional pentanol as cosurfactant by butyl lactate, on the preparation of OAV microemulsions in a system with SDS as anionic surfactant, is investigated. Whereas a narrow region of OAV microemulsion is described for the system with pentanol for a critical ratio 85/15 between water and SDS, butyl lactate leads to wider regions of solubility for different water/surfactant proportions, making easy the preparation of these microemulsions. Besides this advantage, being butyl lactate obtained from renewable resources and considered as a safe and biodegradable product, the microemulsions prepared with this cosurfactant could be applied in technological fields as cosmetic and dermopharmaceutical, where the biological agressivity of pentanol could avoid any practical application. As a complementary study, the influence that 1,3-buryleneglycol as polar cosolvent exert on the microemulsion regions, was also considered. Although according to experimental data given in the paper 1,3-butyleneglycol affects only slightly the OAV region of microemulsions, it can be foreseen that its presence could provide emollient characteristics to the final compositions.     

DETERMINATION OF LONG-TERM STABILITY OF VITAMIN E EMULSION AND FORMATION OF MICROEMULSIONS BY USING LASER LIGHT SCATTERING AND UV ABSORPTION MEASUREMENTS

This paper presents methods of determining the long-term stability of vitamin E emulsion and formation of microemulsions. Several emulsion systems formed by using anionic, zwitterionic and cationic surfactants have been studied in the presence and absence of NaCI. Several conclusions can be drawn: (1) by using UV absorption and particle size measurements, one may be able to predict the long-term stability of an emulsion or the possibility of forming a microemulsion by measuring the initial properties of an emulsion, (2) in order to form a stable vitamin E emulsion or microemulsion, the initial properties of the emulsion should have the following features : (a) the particle size is ≤ 200 nm, (b) the surfactant system has a saturation value ≥ 1 and (c) the surfactant system can dissolve a substantial amount of vitamin E without causing an increase of the emulsion droplet size and (3) the saturation value and the stability of many vitamin E emulsion systems can be increased by adding an optimum amount of NaCI.     

PHASE BEHAVIOR OF MICROEMULSIONS THERMODYNAMICS OF THE R-THEORY

It has been shown previously that the phase behavior of water-oil and amphiphile mixtures can be satisfactorily depicted by the R-theory. This theory, originally developed by Winsor, is based on the qualitative consideration of the interactions of the surfactant relatively to oil and water. Firstly, we show experimental evidence of the power of the R-theory as a tool for optimizing microemulsion formulations. Then, we give a thermodynamical justification of the concepts underlying the R-theory. Lastly, it is shown that, with a very limited number of adjustable parameters, it is possible to calculate series of phase diagrams obtained with ethoxylated alkylphenols, n-alkanes and water.     

W/O微乳液体系稳定条件的研究

研究表明[1～4] ,一个好的微乳液体系要求具有稳定范围宽阔 ,对ｐＨ值和温度的变化不敏感等特点。本文研究目的是为了寻找一个适合制备所需功能氧化物粒子的微乳液体系 ,考察研究Ｔｘ 6～Ｃ4Ｈ9ＯＨ/ｃ Ｃ6Ｈ1 2 /Ｈ2 Ｏ体系Ｗ/Ｏ微乳液在不同条件下能稳定存在的组成范围以及温度和不同ｐＨ值对该稳定组成区域的影响。1　实验部分1 1　实验试剂本实验以Ｔｘ 6(烷基聚氧乙烯酚醚 )为表面活性剂 ,Ｃ4Ｈ9ＯＨ(正丁醇 )为助表面活性剂 ,ｃ Ｃ6Ｈ1 2(环己烷 )为油相。除Ｔｘ 6由上海高桥石化三厂提供外 ,其它试剂均为分析纯。1 2　实验内容在 2…     

CONTINUOUS ABSORPTION OF TOLUENE VAPOR BY MICELLAR SOLUTIONS AND THE RESULTING MICROEMULSIONS

ABSTRACT

Microemulsions consisting of AOT-H₂O-toluene-hexyl carbitol (HC) or butyl carbitol (BC) were investigated in relation to the relative vapor pressure of toluene (P/P_o). The microemulsions generally revealed high (P/P_o). The relatively lower (P/P_o) was only obtained from those containing 10% and 15% AOT at higher levels of HC and BC respectively. From the linear plot of (P/P_o) against the volume fraction of toluene, the transition from micellar solution to microemulsion was evident. This transition phenomenon was also observed in the continuous absorption of toluene vapor. It was concluded chat the microemulsions studied were not efficient in scrubbing toluene vapor, but they were much more effective than their respective micellar solutions.     

脱乙酰甲壳质溶液的粘度及其稳定性

本文研究了脱乙酰甲壳质(CTS)的甲酸、乙酸以及甲、乙酸的异丙醇、乙醇、丙酮溶剂体系的溶液粘度及稳定性,并从溶液的稠度指数K和流动行为指数n来考察其增稠能力和溶液性质。实验表明,含有异丙醇和乙醇溶液的粘度,比不含有机溶剂的溶液的粘度高,而含有丙酮的则较低。有机溶剂的加入,对溶液的稳定性没有明显的影响,CTS甲酸系统的溶液比乙酸系统的溶液具有较好的稳定性。分子量为5.6×10~5CTS的增稠能力不及部分水解聚丙烯酰胺,但优于卡拉胶。CTS溶液属假塑性流体,其K值随溶液存放时间延长而下降,但n值上升,并接近于1。实验发现,抗氧剂维生素C不仅不能增加CTS溶液的稳定性,且对CTS有明显的促进降解作用。     

SDBS／正辛烷／正丁醇／盐水体系中相微乳液微观结构的研究

利用冷冻蚀刻电镜、ＦＴ－ＩＲ、ＥＳＲ和ＮＭＲ方法研究了ＳＤＢＳ／ｎ－Ｃ４Ｈ９ＯＨ／ｎ－Ｃ８Ｈ１８盐水体系中相微乳液微观结构。四种方法均表现随着体系含盐度的增加，中相微乳液微观结构经历了从Ｏ／Ｗ型到Ｂ．Ｃ型，再到Ｗ／Ｏ型的转变。     

聚对苯二甲酸乙二酯(PET)/聚对乙酰氧基甲酸(PHB)共聚酯及同类共聚物序列分布表征的数学统计

由聚对苯二甲酸乙二酯(PET)和对-乙酰氧基苯甲酸制得的PET/PHB共聚酯代表了一类序列结构较一般二元共聚物复杂的共聚体系.在揭示了这类共聚物与序列分布有关的诸概率参数中只有一个是独立的之后,定义了参数B_q来描述此类共聚物的无规度.并指出,共聚物B_q=b时的序列分布,可以从一般二元共聚物无规度B=b时的序列结构加以推断.     

PREPARATION OF W/O/W EMULSIONS IN AN EDIBLE FORM ON THE BASIS OF PHASE INVERSION TECHNIQUE

An attempt was made to provide a basic composition and simple technique for preparing the W/O/W emulsions in an edible form in a view to possible food applications of this type of emulsions. It has been found that TGCR (tetraglyceryl condensed ricinoleate), which is one of the hydrophobic food surfactants, plays a relevant role in developing water/olive oil/water emulsions due to the phase inversion phenomenon occuring when an aqueous solution of glucose or sodium chloride or acetic acid is being introduced successively into the mixture of TGCR and olive oil. The existence of a small amount of sodium chloride (around 10 mM) in the aqueous phase facilitated the development of a water/olive oil/water-type dispersion. The durability of oil layer on the surface of the aqueous compartments in the W/O/W emulsions prepared was much improved by addition of sodium chloride to the aqueous phase.     

高密度聚乙烯／超高分子量聚乙烯共混物高取向薄膜形态结构与力学性能的研究

高密度聚乙烯／超高分子量聚乙烯共混物高取向薄膜形态结构与力学性能的研究张伟广，赵勇，杨德才中国科学院长春应用化学研究所，高分子物理开放实验室，长春，１３００２２）关键词ＨＤＰＥ、ＵＨＭＷＰＥ、共混物、形态结构、力学性能如何提高高分子材料抗张强度和模量...     

K2O对Pt—Sn／Al2O3催化剂表面酸性及MCH脱氢稳定性的影响

利用吡啶吸附－ＩＲ，ＮＨ３吸附－脱附，原位热重积炭，ＤＳＣ等技术并结合甲基环己烷（ＭＣＨ）脱氢活性试验，研究了Ｋ２Ｏ对工业Ｐｔ－Ｓｎ／Ａｌ２Ｏ３催化剂的表面酸性及ＭＣＨ脱氢稳定性的影响，结果表明，Ｋ２Ｏ能有效地调变催化剂的表面酸性，降低其表面酸中心特别是强酸中心的数目；ＭＣＨ脱氢反应的积炭量随Ｋ２Ｏ含量的增加而减少，但催化剂的高温脱氢稳定性与Ｋ２Ｏ含量并不完全呈顺变关系，Ｋ２Ｏ含量应严格控制，当Ｋ     

FORMATION OF O/W EMULSIONS BY SURFACTANT PHASE EMULSIFICATION AND THE SOLUTION BEHAVIOR OF NONIONIC SURFACTANT SYSTEM IN THE EMULSIFICATION PROCESS

Surfactant-Phase Emulsification is a very useful method to produce oil-in-water emulsions having fine and uniform droplets. The mechanism of this emulsification method and the effect of hydrophile-lipophile balance (HLB) of the surfactants on the process of this emuisification were investigated by using phase diagrams of nonionic surfactant/hexadecane/water/1,3-butanediol four component systems.

It was shown that the process of this emulsification begins with the formation of isotropic surfactant solution, followed by formation of oil-in-surfactant clear gel emulsion, and finally by formation of oil-in-water emulsion. By using this emulsification technique, fine oil-in-water emulsions were formed without a need for adjusting of HLB.     

ON THE USE OF SACCHAROSE ESTERS IN THE PREPARATION OF O/W EMULSIONS WITH LIQUID CRYSTALS

The stability and the rheological properties of emulsions prepared with saccharose esters were studied regarding the amounts of the two emulsifiers used and their HLB. The satisfactory stability of these systems has been ascribed to the presence of α-gel phases, evidenced by polarised light microscopy and studied by rheological and water evaporation measurements. The possibility of enclosing pigments such as TiO; and ZnO in these emulsions has also been verified.     

SYNERGETIC EFFECT OF SUCROSE AND ETHANOL ON FORMATION OF TRIGLYCERIDE MICROEMULSIONS

The phase behavior of soybean oil, a nonionic surfactant (ethoxylated monodiglycerides) and an aqueous phase of water containing ethanol, and sucrose was investigated at 35 and 40°C. A minimum concentration of 20 wt% ethanol was required for the formation of isotropic solutions. Addition of sucrose to the aqueous phase decreased the amount of ethanol required to form these solutions. The solubilization mechanism of the oil was investigated by small angle x-ray diffraction and polarized light microscopy. A stable lamellar liquid crystalline phase was formed for a mixture of 75/25 surfactant/sucrose solution (2.5 wt% sucrose). This phase was destabilized with increased concentrations of sucrose and liquid crystalline phases having hexagonal structures were favored at 8.75 wt% sucrose. At a ratio of 55/45 wt% of surfactant/sucrose solution (9 wt% sucrose) hexagonal structures were formed and could be destabilized or destroyed by addition of ethanol. The concept of stabilization and destabilization of liquid crystalline mesophases was applied to the solubilization of triglycerides in aqueous solutions. Two microemulsion regions were identified; oil-in-water (L₁) and water-in-oil (L₂) in systems containing soybean oil, ethoxylated monodiglycerides, and 20 wt% ethanol solution. At 55/45 wt% surfactant/20 wt% ethanol solution,7.5 wt% of soybean oil was solubilized. Addition of 10, 20, and 30 wt% sucrose, at the same ratio of surfactant to ethanol solution, increased the solubility of the oil to 9, 13.5, and 18 wt% respectively. In addition, the size of the L₁ phase increased and moved to the aqueous corner of the phase diagram and the size of the L₂ phase decreased.     

MECHANICAL MODEL FOR TWO-PHASE POLYMER BLEND SYSTEMS WITH THE CHARACTERISTICS OF PHASE INVERSION

For two-phase polymer blend systems, the phase inversion will take place as the blendcomposition is changed. In this paper a mechanical model has been proposed to describe themodulus-composition relation in the phase inversion region. The application of the mechanicalmodel to two polyurethane blend systems has been studied. It was found that the theoreticalprediction for the modulus-composition relation is quite consistent with the experimentalresults. Furthermore, the characteristics of the phase inversion can be determined uniquelyby the parameters involved in the mechanical model.     

煤、焦炭标准物质的稳定性考察及评价

介绍了影响煤、焦炭标准物质稳定性的因素,以实际煤、焦炭标准物质为例,考察了煤、焦炭标准物质的稳定性,介绍了评价煤、焦炭标准物质稳定性的方法,提出了保证煤、焦炭标准物质稳定性的措施。