Effect of Addition of Cosurfactant on the Phase Behaviour of Oil-in-water Aminosilicone Oil Microemulsion

Stable and transparent aminosilicone oil microemulsion of the average particle size below 0.05 micron was prepared. The interaction of the aminosilicone oil, water, complex surfactants and cosurfactant was studied by part pseudotemary phase diagram. The effect of cosurfactants (such as alcohol) and the mechanism of its effect on the phase behaviour of the pseudotemary system were investigated.     

Clouding and Hydrodynamic Behavior of Pluronic-Surfactant Interaction in Aqueous Salt Solutions

Clouding behavior of PEO-PPO-PEO and PPO-PEO-PPO block copolymers were studied in presence of sodium dodecyl sulfate (SDS) and NaCl. Extensive study of Pluronic P84 (EO₁₉PO₄₃EO₁₉) with different salts and ionic surfactants, were carried out using cloud point, viscosity and dynamic light scattering (DLS) measurements. The change in cloud point, as well as the size of P84 micelles in aqueous salt solution obeys the Hofmeister lyotropic series. Results on P84-ionic surfactant mixture indicate stronger interaction in case of SDS compared to those in presence of dodecyl trimethylammonium chloride (DTAC); here interaction seems to diminish in the presence of salts.     

Interfacial Behavior,Structure, and Thermodynamics of Water in Oil Microemulsion Formation in Relation to the Variation of Surfactant Head Group and Cosurfactant

Interfacial behavior, structural, and thermodynamic parameters in relation to the formation of water-in-oil (w/o) microemulsion (μE) with varied surfactant head groups and cosurfactants have been evaluated through dilution technique at different temperature and [water]/[surfactant] mole ratio. Dodecyltrimethylammonium bromide (DTAB), sodium dodecylsulphate (SDS), and polyoxyethylene sorbitan monolaurate (Tween-20) were used as surfactants and n-butanol and n-pentanol were used as cosurfactants. Distribution of cosurfactants between bulk oil and the interface using fixed amount of surfactant at varied [water]/[surfactant] mole ratio and temperature has been studied to evaluate thermodynamic parameters. Associated structural parameters, such as droplet dimension and aggregation number of surfactant and cosurfactant at the droplet interface, have also been evaluated. Spontaneity of the μE formation followed the order DTAB>SDS>Tween-20 for both butanol and pentanol in the studied range of temperature. Correlations of the results in terms of the evaluated physicochemical parameters have been attempted.     

Tuneable Control of Interfacial Rheology and Emulsion Coalescence

Breaking point: Switchable peptide surfactants are used to demonstrate that the extent of cross‐linking in an interfacial surfactant layer can control the rate of emulsion coalescence. Pictured is the rupture of an aqueous thin film where the peptide layer lacks sufficient strength to prevent hole formation, but nonetheless dramatically slows the rate of hole expansion.

     

Study on Osmotic Pressure and Liquid-Liquid Equilibria for Micelle, Colloid and Microemulsion Systems by Yukawa Potential

An equation of state (EOS) was established to study the osmotic pressure and liquid-liquid equilibria for micellecolloid and microemulsion systems. The Carnahan-Starling equation was used for the hard sphere repulsion. The Yukawa potential was used to describe both the attractive dispersion and the double-layer repulsion. By using the established EOS, the osmotic pressures for charged colloid, uncharged micelle, uncharged and weakly charged microemuslion, the phase equilibria for uncharged micelle and charged colloid systems were studied.     

胆红素/HDEHP反相微乳液的制备及应用

磷酸酯;胆红素钙;生物矿化;胆红素/HDEHP反相微乳液的制备及应用     

Molecular Weight Influence on Gelatin Gels: Structure,Enthalpy and Rheology

Summary: This paper deals with the gelation properties of gelatins with various molecular weights. The samples are 4 different extracts from limed bones. We investigated firstly the structural properties: the helix amounts by optical rotation measurements and the enthalpy of helix formation and melting, with the same thermal protocols and for various concentrations. Comparison between the two methods allowed deriving the enthalpy of helix-coil transition and melting. Rheology was performed under the same conditions with a stress controlled rheometer working with a fixed, very small, strain during gel formation, maturation and melting. Correlation between all the measurements confirms the existence of the master curve for storage modulus versus gelatin concentration for all samples investigated.     

Synthesis of ZnS Nanospheres in Microemulsion Containing Cationic Gemini Surfactant

The reverse microemulsion containing cationic gemini surfactant trimethylene‐1,3‐bis(dodecyldimethyl ammonium bromide) (12‐3‐12, 2Br^?) is applied to synthesize ZnS nanospheres. Narrow size distributed ZnS nanospheres with controllable size and uniform morphology are successfully fabricated by direct reaction of ZnCl₂ and Na₂S in the reverse microemulsion systems. Except for the appearance of large aggregates owing to quantum size effects when the incubation time is 2 h, with increasing the incubation time from 12 to 48 h, the diameter of the ZnS nanosphere can be controlled as 20–25 nm and 140 nm, respectively. X‐ray diffraction (XRD), transmission electron microscopy (TEM), and UV‐visible absorption spectroscopy are applied to characterize the resulting ZnS nanoparticles. In the system used in the present study uniform nanosphere morphology can be synthesized, with the incubation time as an important factor in controlling the size of as‐prepared products.     

聚丙烯酰胺对石油磺酸盐／正丁醇混合胶束体系流变性的影响

研究了一定矿化度下，不同分子量、不同水解度的聚丙烯酰胺对石油磺酸盐／正丁醇混合胶事体系的流型、粘度等充变性质的影响。     

Micellization and Effect of Salt Behavior on Meristyl Alcohol Based Bis-Sulfosuccinate Gemini Surfactants in Aqueous Solutions

A series of bis-sulfosuccinate anionic gemini surfactants were synthesized from meristyl alcohol (BSGSMA_1,4; BSGSMA_1,6, and BSGSMA_1,8) containing 4, 6, and 8 methylene chains as different flexible spacer lengths. The chemical structures of synthesized geminis were confirmed by using spectroscopic analytical techniques, viz., elemental analysis, Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance spectroscopy(NMR). Investigations were carried out to examine the effect of different spacer length and different salts (organic and inorganic) on surface and fluorescence properties of prepared gemini surfactants. The results of surface properties shown that surface tension at CMC (?_CMC) and critical micelle concentration (CMC) were reduced and pC₂₀ value was enhanced with increased spacer length. Fluorescence investigations were also revealed the significance of longer spacer with the concluded remarks of higher aggregation number and reduced micropolarity for BSGSMA_1,8 having elongated flexible spacer. The results of salts studies had shown the better results for organic salts as compared to inorganic salts.     

Application of Cryo-Transmission Electronic Microscopy in Sodium Dodecylsutfonate Middle Phase Microemulsion

The middle phase microemulsion of Sodium Dodecylsulfonate / 2-Phenyloxyethanol / heptane / Brine was studied at optimal salinity. The fact that structure nonhomogeneity develops upon standing was revealed by cryo-TEM, polarizing microscopy and small angle X-ray diffraction. The structural complexity in this middle phase microemulsion is demonstrated and the cause of structure transformation from spherical micelles to thread-like ones, then to vesicles and to lamellar phase was analyzed using a concentration gradient of surfactant and cosurfactant in the middle phase microemulsion. This experiment also shows the advantages of this new cryo-TEM method.     

Salt and Heat Induced Aggregation of Diblock Copolymers of Sodium 2-(acrylamido)-2-methylpropanesulfonate and N-Isopropylacrylamide in Aqueous Solutions

Heat and salt induced aggregation of three well-defined double hydrophilic block copolymers (DHBCs) of sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS) and N-isopropylacrylamide (NIPAM) with constant chain length of the PAMPS block (with number-average degree of polymerization, DP _n  = 61) and varying chain length of the PNIPAM block with DP _n  = 11, 23, and 34 synthesized via reversible addition-fragmentation chain transfer (RAFT) controlled radical polymerization was investigated by turbidity, dynamic light scattering (DLS) and ¹H NMR measurements. In the presence of salt or with an increase in temperature, the diblock copolymers form micelles with a PNIPAM core and PAMPS corona. The heat and salt induced aggregation in dilute aqueous solutions dependant on the molecular characteristics of the DHBC (DP _n of the PNIPAM block) was observed. The DHBC becomes amphiphilic as the PNIPAM block loses hydrophilicity at higher temperature above its lower critical solution temperature (LCST). Furthermore, the presence of salt induces salting out effect of the uncharged PNIPAM block. The diblock copolymer thus forms nanosized aggregates at a high temperature or in the presence of salt. These aggregates may be multiple aggregates due to inter-micellar aggregation of the spherical core-corona micelles.     

用乳化度评价中相微乳

用乳化度评价中相微乳;微乳相图;表面活性剂;油相性质;盐宽;用乳化度评价中相微乳     

Thermally-induced Transition in Aqueous Solution of Cationic Surfactant Containing Aromatic Ring

Heat capacities of aqueous solutions of cetyltrimethylammonium (CTA) salicylate, of CTA m-hydroxybenzoate and of CTA p-hydroxybenzoate were measured using a scanning microcalorimeter. Only the salicylate solution exhibited heat-capacity anomaly around 330 K, depending on the heating rate. The transition enthalpy was 3.5±0.2 kJ mol^–1, which was similar to that observed in solution of 1:1 intermolecular compound between CTA bromide (CTAB) and o-iodophenol (OIPh). The enthalpy of formation H_f of the 1:1 intermolecular compound from CTAB and OIPh was determined by measuring the enthalpies of solution of the relevant crystals into ethanol. Positive value _fH=3.0±0.3 kJ mol^–1 was explained from a large difference between the heat capacities of the 1:1 compound and 1:1 mixture of the component crystals.This revised version was published online in November 2005 with corrections to the Cover Date.     

Influence of Mixing Speed in Liquid Crystal Formation and Rheology of O/W Emulsions Containing Vegetable Oils

The process parameters are important in the development of emulsions containing liquid crystals. Thus, we studied the influence of the mixing speed in microscopic and rheological features. Oil-in-water emulsions using vegetable oils and nonionic surfactant were developed employing gradual raise of the mixing speed. It decreased the liquid crystal formation and the density values, and increased apparent viscosity values. The most suitable mixing speed was 600 rpm, since it allowed the attainment of emulsion with better performance and presence of lamellar liquid crystals. However, all emulsions were stable in these experimental conditions and presented pseudoplastic behavior and tixotropy.     

Kinetics for the Reaction between Potassium Ferricyanide and Cobalt Chloride in Aqueous Solution and Microemulsion

The kinetics for the reaction between potassium ferricyanide (K₃Fe(CN)₆) and cobalt chloride (CoCl₂) in aqueous solution and water/bis(2-ethylhexyl) sodium sulfosuccianate (AOT)/isooctane microemulsions were studied by three-wavelength spectrophotometry at 298.2 K. The second-order rate constants (k₂) were calculated from the time dependence of the concentration of reactant K₃Fe(CN)₆. The result showed that the reaction rates in water/AOT/isooctane microemulsions were slower than that in the aqueous solution, and k₂ decreased with molar ratio (ω) of water to AOT in microemulsions, which was interpreted by the transition state theory and confirmed that the reaction took place at the interfaces of the microemulsion water pools.     

Physicochemistry of Mixed Systems of Water/AOT (Surfactant)/Alkanol (Cosurfactant)/Cycloalkanone (Oil): A Detailed Study of Phase Behavior,Salt Effect,and Conductance Properties

Water in oil microemulsion (μE) systems comprising water/AOT ± alkanol (n-butanol to n-dodecanol)/cycloalkanone (cyclopentanone to cycloheptanone, CA5, CA6, and CA7) were physicochemically studied with respect to phase and conductance behaviors. In absence of alkanols, AOT produced large clear zone with the cycloalkanones, compared to linear alkanes. Clear zone was comprised of gel, viscous, and clear fluid. Alkanols increased the fluidity of μE while its clarity was reduced. A maximum two-phase region was observed for n-heptanol (also for formulations with n-octanol). Salts, which reduced the clarity of the μE, followed the order of effectivity: Na⁺ < Mg²⁺ < Al³⁺. A correlation between clarity and turbidity was found irrespective of molecular size of oil, cosurfactant and salt. The influence of water and temperature on the conductance behavior of W/O formulations was studied. The studied systems were found to be less conducting than those with linear alkanes. Energetics and other structural parameters of the studied systems were evaluated from conductance behavior and the use of scaling equations.     

壳聚糖在1-乙基-3-甲基咪唑醋酸盐溶液中的流变行为

离子液体1-乙基-3-甲基咪唑醋酸盐（[EMIM]Ac）对壳聚糖具有良好的溶解能力。利用新一代旋转流变仪哈克MARS-Ⅲ考察了壳聚糖-[EMIM]Ac溶液的稳态流变和动态流变性能。稳态流变结果表明：当低黏均分子量壳聚糖离子液体溶液的质量分数在3%以下时,溶液呈牛顿性流体特征,高于此质量分数时溶液呈假塑性流体特征;壳聚糖离子液体溶液的黏度、结构黏度指数随着温度升高而降低;在同一质量分数下,溶液黏度随壳聚糖黏均分子量的增大而增加,溶液的恒剪切活化能黏流活化能随着剪切速率的增大而降低。动态流变结果表明：溶液的储能模量和损耗模量随着温度的升高而下降,储能模量与损耗模量存在一个交叉点,该交叉点随着温度升高向高频区移动。