Study of the microstructure of o/w creams with thermal and rheological methods

Thermogravimetric and rheological investigations of oil/water (o/w) creams prepared with different types of surface-active agents (non-ionic, non-ionic POE-free, ionic) were carried out. Thermogravimetry was aimed at the indirect study of the water bond mechanism in o/w creams and the influence of the composition, type and concentration of the mixed emulsifier on the binding of water incorporated in the structure (interlamellar, bulk) and on the binding proportions. The microstructural changes during application were studied with respect to the stability of the lamellar bilayer. This revised version was published online in July 2006 with corrections to the Cover Date.     

Water in oil (w/o) and double (w/o/w) emulsions prepared with spans: microstructure,stability, and rheology

The objective was to analyze the microstructure, stability, and rheology of model emulsions prepared with distilled water, refined sunflower oil, and different Spans (20, 40, 60, and 80) as emulsifiers. The effects of the water content and Span 60 concentration were studied. The lowest water contents led to w/o emulsions, whereas higher percentages gave w/o/w emulsions. Microscopy analysis showed that w/o/w emulsions of higher water contents had a lower number of internal water droplets. W/o emulsions were destabilized by coalescence and sedimentation, whereas creaming was observed in unstable w/o/w emulsions. In the last ones, the creaming stability decreased with increasing water content and enhanced with higher Span 60 concentration; the same effect was observed in their viscoelasticity: They were from unstable liquids to stable gels. Solid Spans (40 and 60) produced more consistent w/o/w emulsions at low water contents and more stable systems at high water percentages in comparison with liquid Spans (20 and 80).     

Calorimetric investigation of the formation of ZnS nanoparticles in w/o microemulsions

The enthalpies of precipitation of ZnS nanoparticles within water containing reversed micelles of sodium bis(2-ethylhexyl) solfosuccinate, L-α phosphatidylcholine, tetraethyleneglycol-mono-n-dodecyl ether and didodecyldimethylammonium bromide as a function of the molar concentration ratioR (R=[water]/[surfactant]) were measured by calorimetric technique. The results indicate that the energetic state of ZnS nanoparticles confined in the aqueous core of the reversed micelles is different from that in bulk water. Effects due to nanoparticle size, adsorption of HS⁻ ions on the nanoparticle surface and interactions between nanoparticles and water/surfactant interfaces are discussed. This work has been supported by MURST.     

Vibrational spectra and structure of mixed alkali borotungstate glasses: Evidence of mixed alkali effect

Mixed alkali borotungstate glasses with xLi₂O–(30 − x)Na₂O–10WO₃–60B₂O₃ (0 ≤ x ≤ 30) composition were prepared by melt quench technique. FT-IR and Raman spectroscopic studies were employed to investigate the structure of all the prepared glasses. Acting as complementary techniques, both IR and Raman measurements revealed that the network structure of the present glasses mainly based on BO₃ and BO₄ units placed in different structural groups. Raman spectra confirm the IR results regarding the presence of tungsten ions mainly as WO₆ groups. In the present work, the mixed alkali effect (MAE) has been investigated in the above glass system using FTIR and Raman studies.     

Influence of nonionic emulsifier included inside carboxylated polymer particles on the formation of multihollow structure by the alkali/cooling method

The influence of nonionic emulsifier, included inside styrene-methacrylic acid copolymer [P(S-MAA)] particles during emulsion copolymerization, on the formation of multihollow structure inside the particles via the alkali/cooling method (proposed by the authors) was examined in comparison to emulsifier-free particles. It was clarified that the nonionic emulsifier included inside the P(S-MAA) particles eased the formation of multihollow structure.Part CCL of the series studies on suspension and emulsion     

Hydrothermal synthesis and structure determination of the new vanadium molybdenum mixed oxide V1.1Mo0.9O5 from synchrotron X-ray powder diffraction data

A new vanadium molybdenum mixed oxide V_1.1Mo_0.9O₅ [V(V)_0.2V(IV)_0.9Mo(VI)_0.9O₅] has been synthesized, as a pure phase, via hydrothermal methods in the presence of molybdic acid and vanadyl sulfate. Its crystal structure has been solved ab initio from high-resolution powder diffraction data collected at the ESRF beamline ID31. This compound crystallizes in the monoclinic symmetry, space group C2/m, with cell dimensions , , , β=90.625(3)° and Z=2 per formula. The structure consists of double strings of VO₅ square pyramids sharing edges and corners along [100] and [010], and more weakly bound along [001]. In this latter direction, the bond (V,Mo)-O=2.377 Å, while remaining long, leads for the first time to the interpenetration of the apical oxygens of the [(V,Mo)₂O₅]_n layers, resulting in a three-dimensional (3D) structure closely related to R-Nb₂O₅. This structure will be compared to the pure layer structure of V₂O₅ where this bond reaches 2.793 Å.     

反应性乳化剂存在下的五元苯丙乳液共聚合

采用反应性乳化剂SE-10N,通过正交实验及单因素实验确定了以苯乙烯、甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸和丙烯腈为单体的五元无皂苯丙共聚乳液的组成及聚合工艺。所制得的无皂乳液稳定,其乳胶粒大小均匀,粒径为50~60nm,比同组成的有皂乳液乳胶粒的粒径稍小。乳液涂膜透明、硬度达H级;其硬度、耐水性及钙离子稳定性均较同组成有皂乳液的好。     

Solution of telechelic ionomers in water/AOT/oil (w/o) microemulsions: a static and dynamic light scattering study

Static and quasielastic light-scattering measurements of endsulfonated polyisoprene in a water in oil (w/o) microemulsions were used to characterize the structure and diffusion properties of this complex system. The hydrophilic end groups of the polymer stick to the surfactant covered oil/water interface, thus bridging the water droplets. This structure formation decreases the mobility of the aqueous nanodroplets and polymer molecules. At interdroplet distances larger than the end-to-end distance of the ionomer chain a decrease of the osmotic modulus is observed. It can be explained by a depletion force of free ionomer chains acting on the nanodroplets. With increasing polymer concentration structure formation of the microemulsion is observed at nanodroplet concentrations where the ionomer chains just fit the average separation of two nanodroplets.     

用混合乳化剂UE20/PVA制备的水包油型生漆乳液的性能

以漆酚基乳化剂(UE20)和聚乙烯醇(PVA)为混合乳化剂制备了水包油(O/W)型生漆乳液(RLE), 研究了UE20与PVA的质量比、混合乳化剂质量分数(wME)、水与天然生漆(RL)的质量比、温度和贮存时间对RLE性能的影响, 并用透射电镜观察了wME对RLE粒子的大小及形态的影响. 结果表明, RLE的黏度随着PVA的增加而增大; 当wME≤6.7%时, RLE表现出假塑性流体的特征, 其黏度随着wME的增大而增大, 乳液的稳定性增强; 而当wME≥10.0%时, RLE则表现出膨胀型流体的特征, 乳液的黏度较低; 随着温度的升高及水的用量增加, RLE粒子间相互作用减弱, 乳液的稳定性降低. 正交实验结果表明, 影响RLE的黏度及稳定性的顺序为wME＞mH2O∶mRL＞mUE20∶mPVA＞乳化温度. 随着wME的增大, RLE粒子的粒径减小, 其形态也由不规则的形状转变为球形粒子.     

Analysis of dielectric relaxations of w/o emulsions in the light of theories of interfacial polarization

An attempt is made to apply dielectric theories of interfacial polarization to observations of dielectric relaxations for W/O emulsions. Approximate formulas for disperse systems in a W/O type were derived from the two theories: one proposed by Maxwell and Wagner for dilute disperse systems of spherical particles, and the other developed by Hanai for concentrated disperse systems. Dielectric measurements were carried out on concentrated W/O emulsions prepared from kerosene and distilled water or KCl aqueous solutions by minimal use of emulsifiers. Marked dielectric relaxations were observed with the emulsions, the dielectric parameters having been determined to characterize the relaxation data. Phase parameters such as relative permittivity, electric conductivity and volume fraction of the disperse phase were evaluated from the dielectric parameters by use of the approximate formulas of the respective theories. The phase parameters evaluated and the frequency dependence of complex permittivity of the W/O emulsions deduced from the theory for concentrated disperse systems are in excellent agreement with the observed data in comparison to that for dilute disperse systems. It is concluded that the dielectric relaxations due to the interfacial polarization of disperse systems of spheres are explained satisfactorily by the theory for concentrated disperse systems.     

The structure of CeAlO3 by Rietveld refinement of X-ray powder diffraction data

The room temperature structure of perovskite CeAlO₃ has been reinvestigated by X-ray powder diffraction. The Rietveld refinement has confirmed the tetragonal symmetry; but revealed a super cell, a=5.32489(6) Å and c=7.58976(10) Å, with the space group I4/mcm. In CeAlO₃, the distortion from the ideal cubic perovskite is caused by the cooperative tilting of the AlO₆ octahedra around the primitive cubic [001]_p-axis.     

金属皂的晶体结构

钠、钾以外金属的高级脂肪酸盐通称金属皂。它们兼具金属盐和脂肪酸的特性,在工业上广泛用作为塑料助剂(热稳定剂、润滑剂等)、油漆催干剂、增稠剂、防水剂、脱模剂,爽滑剂等[1]。金属皂的许多特性随脂肪链长度和金属种类的不同而变化。稀土、碱土和锌、镉、铅等金属皂是重要的PVC热稳定剂和润滑剂[2,3]。前文[4,5]已报道了稀土金属皂结构的红外光谱和X 射线衍射谱,本文报道镁、钙、锶、钡、锌、镉、铅与棕榈酸、肉豆蔻酸、月桂酸、癸酸锌、辛酸形成金属皂结构的X 射线衍射谱。1　实验部分1 1　金属皂合成采用复分解法[1]合成,产物均…     

Synthesis and structure analysis of tetragonal Li7La3Zr2O12 with the garnet-related type structure

We have successfully synthesized a high-purity polycrystalline sample of tetragonal Li₇La₃Zr₂O₁₂. Single crystals have been also grown by a flux method. The single-crystal X-ray diffraction analysis verifies that tetragonal Li₇La₃Zr₂O₁₂ has the garnet-related type structure with a space group of I4₁/acd (no. 142). The lattice constants are a=13.134(4) Å and c=12.663(8) Å. The garnet-type framework structure is composed of two types of dodecahedral LaO₈ and octahedral ZrO₆. Li atoms occupy three crystallographic sites in the interstices of this framework structure, where Li(1), Li(2), and Li(3) atoms are located at the tetrahedral 8a site and the distorted octahedral 16f and 32g sites, respectively. The structure is also investigated by the Rietveld method with X-ray and neutron powder diffraction data. These diffraction patterns are identified as the tetragonal Li₇La₃Zr₂O₁₂ structure determined from the single-crystal data. The present tetragonal Li₇La₃Zr₂O₁₂ sample exhibits a bulk Li-ion conductivity of σ_b=1.63×10⁻⁶ S cm⁻¹ and grain-boundary Li-ion conductivity of σ_gb=5.59×10⁻⁷ S cm⁻¹ at 300 K. The activation energy is estimated to be E_a=0.54 eV in the temperature range of 300–560 K.     

Characterization of the gel structure in a nonionic ointment by small angle X-ray diffraction

The structure of systems containing equal weights of cetylalcohol, stearylalcohol and the nonionic surfactant poly(oxyethylene)₂₀-glycerolmonostearate is studied as a function of the water concentration. In this paper mainly results are presented obtained by small angle X-ray-diffraction. Up to ± 22% (w/w) water several coexisting phases were observed. From ± 22% to ± 55% water a lamellar structure is found. This structure consists of lipophilic bilayers formed by the hydrocarbon tails of cetylalcohol, stearylalcohol and the surfactant, alternated by hydrophilic layers formed by the polyoxyethylene glycerol chains, the hydroxyl groups of cetylalcohol and stearylalcohol and water. From the swelling behaviour the density of the gel structure (0.9 g/cm³) and the cross sectional area of the molecules in the bilayers (0.19 nm²) have been calculated. It is concluded that the hydrocarbon chains are in a crystalline, state and are placed perpendicular to the lattice plane. Upwards of ± 55% water the lamellar phase disperses in the excess of water.     

Molecular structure of decamethylgermanocene in the solid state

The low temperature X-ray structure analysis of decamethylgermanocene reveals two independent molecules in the unit cell, both of which have a bent sandwich structure with angles between the planes of the two C₅Me₅ rings of 31.26(0.09)° and 31.55(0.10)°, respectively. The perpendicular germanium to ring distances are 220 pm, corresponding to Ge-C bond lengths ranging from 240 to 266 pm.     

Study of CCl3F hydrate formation and dissociation in W/O emulsion by differential scanning calorimetry and X-ray diffraction

Differential scanning calorimetry (DSC) and time-resolved synchrotron X-ray diffraction as a function of temperature (XRDT) were combined in a novel way in order to study conditions of formation and the amount of gas clathrate formed in dispersed systems. The formation and dissociation of trichlorofluoromethane hydrate CCl₃F·(H₂O)₁₇ in a water-in-oil emulsion were followed by using these combined techniques. An emulsion containing 3 wt.% NaCl was submitted to a cooling and heating cycle between 20 and −50 °C. During cooling, a single exothermic peak at −43 °C, found in DCS thermograms was assigned to the freezing of under-cooled water droplets; however, no noticeable signal related to hydrate crystallisation was detected. Conversely, during subsequent heating, the progressive melting of ice was followed by an endothermic signal indicative of hydrate decomposition. From X-ray diffraction performed on an emulsion sample, it was possible to identify the exact condition of CCl₃F·(H₂O)₁₇ formation. XRDT diffraction patterns clearly demonstrated that only ice crystallised in the aqueous droplets during cooling and that the hydrate only formed during heating simultaneously with melting of ice. From the solid–liquid phase diagrams of systems H₂ONaCl and CCl₃FH₂ONaCl and from the DSC and XRDT experiments, the composition of the droplets was deduced. The upper limit of the amount of hydrate that could form in the system was calculated.     

Tri-n-butyltin carboxylate derivatives of para-substituted phenyl-ethanoic acids: synthesis, characterization and X-ray structure determination

The tributyltin esters of 4-(ethyl)-phenyl-ethanoic acid and 4-(isopropyl)-phenyl-ethanoic acid have been prepared as model compounds of the repeating unit of the related stannylated polystyrenic derivatives. Both the products were fully characterized by proton and carbon NMR two-dimensional techniques. FT-IR spectra show in the solid state carboxylated moieties bridging R₃Sn groups with the metal atom expanding its coordination number, this structure being destroyed in solution. The supramolecular arrangement of the products in the solid state has been investigated by X-ray diffraction, which confirms the pentacoordination at tin in both the products, and indicates a different spatial arrangement of the alkylated aryl groups, as evidenced also by the slightly different thermal properties.     

Lipophilicity assessment of basic drugs (log P(o/w) determination) by a chromatographic method

A previously reported chromatographic method to determine the 1-octanol/water partition coefficient (log P(o/w)) of organic compounds is used to estimate the hydrophobicity of bases, mainly commercial drugs with diverse chemical nature and pK(a) values higher than 9. For that reason, mobile phases buffered at high pH to avoid the ionization of the solutes and three different columns (Phenomenex Gemini NX, Waters XTerra RP-18 and Waters XTerra MS C(18)) with appropriate alkaline-resistant stationary phases have been used. Non-ionizable substances studied in previous works were also included in the set of compounds to evaluate the consistency of the method. The results showed that all the columns provide good estimations of the log P(o/w) for most of the compounds included in this study. The Gemini NX column has been selected to calculate log P(o/w) values of the set of studied drugs, and really good correlations between the determined log P(o/w) values and those considered as reference were obtained, proving the ability of the procedure for the lipophilicity assessment of bioactive compounds with very different structures and functionalities.     

The Na2O-SrO-B2O3 diagram in the B-rich part and the crystal structure of NaSrB5O9

The subsolidus phase relations in the B-rich part of the ternary system, Na₂O-SrO-B₂O₃, are investigated by the powder X-ray diffraction method. Four ternary compounds: NaSrBO₃, NaSr₄B₃O₉, Na₃SrB₅O₁₀ and NaSrB₅O₉ were found in it, the two lasts are new. NaSrB₅O₉ crystallizes in the monoclinic space group P2₁/c, with the lattice parameters a=6.4963(1) Å, b=13.9703(2) Å, c=8.0515(1) Å, β=106.900(1)°. Na₃SrB₅O₉ is also monoclinic, space group C2, a=7.290(1) Å, b=13.442(2) Å, c=9.792(1) Å, β=109.60(1). NaSrB₅O₉ is isostructural with another pentaborate NaCaB₅O₉, and its structure was refined by Rietveld method based on the structural model of NaCaB₅O₉. The fundamental building units are [B₅O₉]³⁻ anionic groups, forming complex thick anionic sheets, extending parallel to the ac plane. The Na and Sr atoms are all eight-coordinated with O atoms, forming trigonal dodecahedra. The [NaO₈] polyhedra are distributed between the B-O sheets, while the [SrO₈] polyhedra located in the sheets and connect with each other by edges to form infinite chains along the c-axis.     

Experimental and theoretical investigation on the correlation between aqueous precursors structure and crystalline phases of zirconia

Nanometer zirconia powders were prepared by the precipitation method at different pHs and different reaction temperatures. X-ray results show that monoclinic zirconia is favored at pH 4 while tetragonal zirconia is favored at pH 9.5 at room temperature, and monoclinic zirconia is also favored at pH 9.5 and 70 °C reaction temperature, with the slow addition of alkali. Four models of zirconium complexes were applied to simulate the structural monomers in different pH solutions. Geometric parameters and Mulliken charge population were calculated by optimizing these complexes using the density functional theory (DFT/B3LYP). Theoretical analyses show that if Model I ([Zr(OH)₂(H₂O)₄]²⁺ monomers) is favored in the aqueous precursor solution, it will be preferentially polymerized into monoclinic precursor structure irrespective of slow or quick alkali addition. Contrarily, if Model IV ([Zr(OH)₇]³⁻ monomers) is major in the aqueous precursor solution, tetragonal precursor structures are favored irrespective of slow or quick alkali addition. When Model II ([Zr(OH)₄(H₂O)₂]⁰ monomers) and Model III ([Zr(OH)₆]²⁻ monomers), respectively, predominate in the aqueous precursor solution, they will be preferentially polymerized into tetragonal precursor structure at slow alkali addition, however, for quick alkali addition, they will be preferentially polymerized into monoclinic precursor structure. Our theoretical models well explain the present experimental results as well as previous experimental results, and allow building up a correlation between aqueous precursor structures and crystalline phases of zirconia.