Electrorheological Effects in Lecithin Organogels with Water and Glycerol

The effect of an external electric field on ternary mixtures consisting of lecithin, n-decane, and small amounts of polar additives (water or glycerol) has been studied by oscillating rheology, polarizing microscopy, and electric birefringence. It is shown that an electric field that is applied induces a so-called electrorheological (ER) effect, i.e., an increase in the viscosity and dynamic shear moduli of all the examined mixtures. The ER effect is absent in solutions of nonoverlapping micelles. The electric field causes the formation of fiber-like structures in the interelectrode gap. The ER effect becomes evident at a critical field of about 40 and 100 V/mm for water- and glycerol-containing organogels, respectively. In the latter case, a region of the reproducible and stable ER effect is extended up to 1700 V/mm, which is 3-4 times greater than that observed in the jelly-like phases with water. The buildup, as followed from birefringent measurements, includes fast and slow processes. Those correspond to both the local motions of parts of micellar chains and the restructuring of the whole network under the action of an external electric field. The ER response depends on the molar ratio of the polar additives to lecithin. Diagrams describing the behavior of ternary mixtures under the electric field have been constructed. They differ for water- and glycerol-containing organogels. The dependence of the stable ER effects on the molar ratio of glycerol to lecithin has a maximum in the vicinity of the phase separation of the homogeneous organogel, whereas for water-containing systems there is a gradual increase up to and including mixtures with the solid precipitate. A new rheological regime has been first established for solutions of polymer-like micelles. This feature is the square-root scaling of the dynamic moduli with the frequency. Such a scaling is inherent in polymers. A possible mechanism is considered, basing on the ordering of cylindrical micelles under the action of an external electric field. Copyright 1999 Academic Press.     

Lecithin Organogels Containing Poly(ethylene glycol) Monolaurate

The effect of added poly(ethylene glycol) monolaurate (PEGML) on the formation and properties of lecithin organogels composed of polymer-like micelles was studied by the methods of dynamic rheology and the Fourier transform IR spectroscopy. It was established that the addition of even small amounts of PEGML causes a significant decrease in viscosity, whereas the elastic properties of organogels remained almost unchanged. The analysis of the scaling dependences indicated that the formation mechanism of polymer-like lecithin micelles remained also unchanged. Spectral studies revealed that the PEGML molecules affect intermolecular hydrogen bonding during their incorporation into micelles, thus stabilizing micellar structure. This effect is caused by the partial dehydration of the lecithin polar region. This leads to a decrease in the number of hydrogen bonds or their weakening and, as a result, to the disintegration of polymer-like lecithin micelles into shorter micellar aggregates.     

Organogels from a vitamin C-based surfactant

A new double chained surfactant, 2-octyl-dodecanoyl-6-O-ascorbic acid (8ASC10), with a L-ascorbic acid unit as the polar headgroup was synthesized for the first time. The behavior of the compound in the dry solid state has been characterized through DSC, XRD, and SAXS measurements. The surfactant forms stable viscous organogels in the presence of suitable organic solvents and also water-induced organogels upon addition of water to the organogel. These mixtures show shear-thinning properties and are birefringent. The behavior and properties of the organogels have been studied through rheology, DSC, and SAXS experiments. The organogels possess the same antioxidant properties of the original L-ascorbic acid ring and can be used to solubilize and protect valuable organic molecules.     

Crude Oil Hydrocarbon Group Separation Quantitation

Abstract

The petroleum industry like most other industrial segments are continuously developing new and sophisticated techniques of analysis and at the same time are working to automated routine techniques. In the petroleum industry, the source of supply has generally become less stable and economics has dictated new thinking, both in processing and in the analysis of composition to support these new trends. In addition, this industry is faced with having a new raw material, shale oil, and coal liquids, in the near future.     

Organogels from water-in-oil microemulsions

A new family of organogels is described. They originate from water-in-oil microemulsions, from which the name microemulsion gels or microemulsion-based gels is derived. Two different types of such gels are presented here, referred to asgelatine gels andlecithin gels, respectively. In the case of gelatine gels, the initial ternary system typically consists of isooctane, AOT (bis 2-ethylhexyl sodiumsuccinate) and water; gelation is induced by solubilization of gelatine in the water microphase above a critical concentration. In the case of lecithin gels no polymeric material is needed. Starting from a reverse micellar solution of lecithin (50–200 mM) in an organic solvent, gelation is induced by the addition of a small amount of water. The molar ratio of water to lecithin typically varies between 1 and 12 for the 50 different solvents investigated to date. These gels are isotropic, thermoreversible and optically transparent.For both microemulsion gels the influence of the concentration of the components on gelation is presented in the form of preliminary phase diagrams.The physico-chemical properties of these organogels were characterized using a variety of techniques such as NMR, DSC, dynamic shear viscosity measurements, and light scattering. Based on these measurements, preliminary models for the structure of these novel systems were developed.It is possible to co-solubilize a variety of reactive molecules in these gels. Therefore, it may be possible to use these organogels for a number of chemical, pharmaceutical, and cosmetic applications.Paper presented at the Workshop on Ringing Gels and Cubic Phases, Bayreuth, October 25–26, 1988.     

Castor Oil Based Organogels: I. Synthesis,Swelling, and Network Parameters

Linear and branched polyesters were prepared by transesterification of methyl recinoleate without or with diethylene glycol, trimethylol propane or pentaerithirtol for different durations. Molecular weight of the synthesized polyesters were determined using gel permeation chromatography and hydroxyl number. Their chemical structure were characterized by FTIR. Crosslinked polyesters were prepared using different weight ratios of trimethylolpropane triacrylate in presence of benzoyl peroxide initiator. These organogels were characterized through soluble fraction and toluene sorption capacity. Swelling kinetics and network parameters including polymer solvent interaction, effective and theoretical crosslink densities, average molecular weight between crosslinks and modulus of elasticity were determined.     

Dopant-Mediated Interactions in a Lecithin Lamellar Phase

Interactions induced by dopants in a lamellar phase constructed from the lecithin and water are analyzed by the small angle x-ray scattering (SAXS) technique. From SAXS patterns, scattering peak or curve shape changes disclose information on phase structure as well as the interactions between dopant and host matrices. At a certain concentration, two amphiphilic tri-block copolymers (Pluronic P123 and F127) as dopants squeeze themselves into the lecithin bilayers with PPO hydrophobic blocks and produce various effects on the lamellar phase depending on the length of PEO hydrophilic groups. Coexistence of two different lamellar phases is observed in P123-doped systems.     

苯乙烯-异戊二烯/丁二烯-苯乙烯嵌段共聚物的热裂解色谱-质谱分析

苯乙烯-异戊二烯/丁二烯-苯乙烯嵌段共聚物的结构如下:     

青海出露油砂沥青的烃类组成分析

利用气相色谱(GC)和气相色谱／质谱联机(GC／MS)检测了青海出露油砂沥青的烃类组成与分布。结果表明，其为陆源湖相有机质生成的原油经生物氧化降解形成的。由于所处的独特地理、地质环境，其生物氧化降解程度低，饱和烃含量甚高，分布规整，轻质组分很多，明显不同于其它地区的油砂沥青。鉴于其特殊的化学组成与分布，该油砂矿必须采用新的方式进行开采。     

Organogels from ABA triblock copolymers

ABA triblock copolymers with two polystyrene endblocks connected by a poly(ethylene/butylene) midblock form highly elastic gels in a solvent which is incompatible for the endblocks but a good solvent for the midblock, for example, paraffin oil. In this situation the polystyrene endblocks aggregate into micelles. The midblocks can either form loops or build up bridges between different micelles; thus, domains and networks of interconnected micelles are produced. We have studied organogels of this kind consisting of a polymer with a molar mass of 90,000 and a styrene content of 31% per weight (Kraton G 1650) in paraffin oil. Rheological, calorimetric (differential scanning calorimetry) and small-angle X-ray scattering experiments were performed on these systems. An interesting result of our work which was not described previously is that the size (r˜ 6.8 nm) and the separation (d˜ 36 nm) of the micellar aggregates does not seem to be influenced by the block copolymer content in the concentration range investigated. Received: 12 March 2001 Accepted: 5 April 2001     

气相色谱-质谱法测定变压器油正构烃含量

环烷基油是生产高性能变压器油的优质原料,以此为基础油生产的变压器油其凝点一般都小于-40℃,而变压器油在使用过程中对凝点(即低温流动性)有着非常高的要求,凝点的高低直接影响着油品的物理化学性能及电器性能。而油品的低温流动性与其组成中的正构烃(蜡)含量密切相关,据有关     

Organogels Derived from Potassium 8-Nitroquinolinecarboxylate

A new class of organogels derived from potassium 8-nitroquinolinecarboxylate was selectively formed in THF/MeOH （V：V=1： 1）, and their superstructures were characterized by atomic force microscopy, scanning electron microscopy and transmission electron microscopy.     

原油饱和烃指纹的内标法分析

采用内标法建立了原油中正构烷烃、生物标志物(甾、萜烷类)的分析方法。确定了样品前处理方法和组分定性定量方法。讨论了柱层析分离能力。结果表明,所有饱和烃组分均流入第一部分流出液F1中,分离能力较为满意。对48种甾、萜烷类生物标志物组分以及姥鲛烷、植烷和正构烷烃等进行了定性确认,定性化合物数量多,信息量大,易于据此进行可靠的油指纹分析鉴别。32个正构烷烃组分相对标准差为1.2%～7.4%;45个生物标志物组分相对标准偏差为2.5%～9.2%。分析精密度较好,满足油指纹鉴别需要。正构烷烃回收率为73%～116%;生物标志物为84%～106%;回收率结果较为满意。正构烷烃方法检出限为7.0μg/g;生物标志物为0.65μg/g,满足原油样品分析要求。通过本方法对自不同和相同平台的原油样品进行饱和烃浓度分析,并采用浓度数据进行鉴别,结果与实际情况相符。     

Organogels derived from tetranitrated crown ethers

[reaction: see text] The 3,3',4'4'-tetranitrodibenzocrown ethers TNDB24C8 and TNDB30C10 form organogels with chloroalkanes at 3% w/v. Atomic force microscopy and scanning electron microscopy have been used to characterize the superstructure of the gels. Gels prepared using TNDB30C10 and CHCl(3) are more fibrous and are ordered into elongated domains attributable to exposed parts of intermingled fibers. Differential scanning calorimetry shows that the gel aids in the formation of supercooled CHCl(3) (DeltaT = 21 K, DeltaH(av) = 19.0 +/- 1.5 kJ mol(-)(1)) and that the gel liquefies at 307 K.     

Organogels from liquid and gaseous hydrocarbons

It is shown that n-butane, condensed in autoclave, can readily dissolve the anionic surfactant AOT (bis-2-ethylhexylsodium sulphosuccinate) and that this solution solubilizes water up tow ₀=molar ratio/water-AOT).The microemulsion can be transformed into a gel by solubilizing gelatin in the water microphase. These microemulsion gels are characterized by a very high viscosity (several hundred poise). However, the partial vapour pressure of the n-butane component in the gel is as high as in the liquid state. Infrared studies show that part of the water in the gel is still free.Stability diagrams of this system and¹H-NMR studies to assess the state of water are presented. Analogously to reverse micelles from liquid hydrocarbons, the chemical shift of water protons is shifted to higher fields with respect to bulk water. This effect increases with decreasing temperature andw ₀. At loww ₀ values (< 10), a part of the water in the micelles does not freeze even at –35°C.Due to the rapid evaporation of n-butane from the gel, gelatin films can be prepared simply by casting. Differential scanning calorimetry studies of the gels (from n-butane as well as from isooctane and other hydrocarbons) show that the films have a thermal stability comparable with, and sometimes higher than, gelatin films prepared by conventional methods. Preliminary permeability studies of these films with solutions of amino acid derivatives and with gas such as nitrogen and helium are presented.     

Phasenumwandlungserscheinungen in Lecithin/Wasser-Systemen

1. By means of differential-scanning-calorimetry the phase transition temperatures and -enthalpies were determined and evaluated for the three following lecithin/water systems: 1,2-dimyristoyl-lecithin/water; 1,2-dipalmitoyl-lecithin/water; 1,2-distearoyllecithin/water.
2. The preparation of the lecithin/water mixtures was made by adsorption of water from the gaseous phase. The adsorption isotherms were evaluated by the BET equation.
3. Four phase transitions were found for the monohydrates of the lecithins. The parameters depend systematically on the length of the alkyl residues.
4. In the heterogeneous two phase region the main-transition and the pre-transition occurred. The thermodynamical parameters of both transitions depend on the alkyl chain length.
5. Whole the results refer to the conclusion that the lecithin head group hydration is a stepwise process. The hydration of the first shell is finished if 5 to 6 molecules water per molecule lecithin are present, while the second hydration shell is complete when about 13 water molecules are adsorbed

     

Hydrocarbon Type Separation of Lubricating Base Oil in Multigram Quantity by Preparative HPLC

Abstract

A preparative High Pressure Liquid Chromatography (HPLC) method has been developed to separate lubricating base oil into its three major hydrocarbon fractions: saturates, aromatics, and polars. The results are directly comparable to ASTM Method D2007, hydrocarbon type analysis by gradient elution liquid chromatography. The new method employs a preparative HPLC unit with dual, radially compressed columns consisting of clay and alumina/silica gel columns. Multigram quantities of minor components (1 to 2% by wt.) of a base oil can be isolated for further study.     

Phasenumwandlungserscheinungen in Lecithin/Wasser-Systemen

1. By means of the differential scanning calorimetry technique the phase diagram of 1,2-dipalmitoyl-lecithin/water was determined. The own results are discussed on a pure thermodynamical point of view together with the literature data. The contradictions which are obvious from the existence of different phase regions in the literature are considered.
2. The thermodynamical parameters of the pre-transitions as a function of the lecithin chain length was analysed and compared. The kinetics of the pre-transition was investigated.