超临界二氧化碳中的胶束催化技术进展

介绍了超临界二氧化碳(scCO2)胶束催化技术的研究进展：scCO2胶束及其相特征、CO2表面活性剂及scCO2胶束催化技术的应用与工艺开发。scCO2胶束及其相特征对于设计高效的亲CO2表面活性剂及研究scCO2胶柬催化作用具有重要指导意义。scCO2胶束的相特征主要是温度、压力和胶束含水比的函数。指出了开发亲CO2表面活性剂的一些基本原则,其中降低表面活性剂在H2O／CO2表面的界面张力和提高活性剂的吸附能力要比提高溶解度更为重要。scCO2胶束催化技术可以明显提高催化反应活性,适合于开发原位分离反应工艺。建议加强scCO2胶束催化技术的研究及相关工艺开发。     

Effect of surfactants on the thermodynamic properties of Methyl Orange dye in buffered solutions

The apparent thermodynamic parameters of ionisation and the association constants of the two forms of Methyl Orange were evaluated in the presence of different surfactants (TX-100 as nonionic, CTAB as cationic and SDS as anionic). The enthalpy of ionisation of the dye in aqueous solution and at different surfactant concentrations is obtained from a novel thermochromic method and is found to decrease in aqueous medium in CTAB and TX-100 micelles and to increase in the case of SDS micelles. The apparent ionisation constant of the dye is evaluated spectrophotometrically for each surfactant concentration and type. The apparent Gibbs free energy, entropy of ionisation and association constants are also calculated. The results are discussed in light of the stabilisation of the two forms of the dye in the micellar core of the different surfactants and their effect on properties of the bulk solution is examined.     

反胶团酶催化研究新进展

评述了近年来反胶团酶催化研究的新进展。在AOT/异辛烷反胶团中加入非离子型表面活性剂如Tween 85、小相对分子质量聚乙二醇等可有效降低酶与表面活性剂间的静电和疏水作用 ,显著提高酶的活性。对AOT进行化学修饰及合成结构与磷脂类似的新表面活性剂以用其构建新的反胶团体系 ,酶的活性较常用的AOT/异辛烷反胶团体系有显著提高。在反胶团酶反应动力学研究中考虑水含量或底物在反胶团表面吸附的影响等 ,提出了进一步研究的设想 ,包括开发新型表面活性剂以进一步提高酶的活性和稳定性及有利于产物分离     

超临界CO2萃取海星皂甙

用正交实验法,通过方差分析,建立并优化了超临界CO2/表面活性剂萃取海星皂甙的工艺。在以浓度为0.075 moL/L的二辛酯琥珀酸磺酸钠(AOT)/辛基酚聚氧乙烯醚(TX-10)组成的复合表面活性剂的正丁醇/乙醇/水多元溶液为助溶剂,萃取压力30 MPa,萃取温度333 K,萃取时间2 h,采取两级分离,分离器(1)的温度为328 K,压力15 MPa,分离器(2)的温度为338 K,压力5 MPa的优化工艺条件下,海星皂甙的萃取率为1.33%,萃取物中海星皂甙质量分数为59.01%,溶血指数为19 231。与乙醇〔w(CH3CH2OH)=85%〕萃取相比,超临界CO2萃取海星皂甙的萃取率提高到1.2倍,质量分数提高到2.0倍,溶血指数提高到1.5倍,所萃取的海星皂甙具有显著的细胞毒性,充分体现了超临界CO2萃取的“绿色”特性。     

GSS362/TX-100复配体系在水中的溶液行为研究

研究了1,3-丙二醇双子琥珀酸二异辛酯磺酸钠(GSS362)和辛基酚聚氧乙烯醚(TX-100)复配物在水中的表面性质和胶束化行为,并对理想混合临界胶束浓度以及混合体系中各组分在表面吸附层和胶束中的组成、相互作用参数和热力学参数进行分析计算。结果表明,复配物在水溶液中不存在协同效应,但是TX-100的加入明显降低了GSS362的临界胶束浓度,混合胶束的形成为自发过程,胶束中GSS362与TX-100分子具有较弱的相互作用,胶束中富含非离子表面活性剂TX-100。     

Investigation on multiple-melting behavior of nano-CaCO3/polypropylene composites

The multiple melting-peak behavior of polypropylene (PP) in nano-CaCO₃/PP composites and modified nano-CaCO₃/PP composites were investigated under the condition of isothermal crystallization and nonisothermal crystallization. The result indicated that the addition of nano-CaCO₃ markedly increased the crystallization temperatures of PP and induced the formation of the β-crystal of PP. The crystallization temperatures of nano-CaCO₃/PP composites modified by reactive monomers were further increased, but the melting-peak intensity of the β-crystal of PP was not greatly influenced. While in the presence of dicumyl peroxide, nano-CaCO₃/PP composites modified by reactive monomers led to the significant increase in the melting-peak intensity of the β-crystal of PP. The double melting-peak of PP was observed, which was attributed to the formation of two kinds of different crystallization forms of α-crystal or β-crystal during the crystallization of PP. With the increase of crystallization temperatures, the double melting-peak moved toward the high-temperature side. The intensity of high-temperature melting peak was higher than that of low-temperature melting peak in nano-CaCO₃/PP composites. While in modified nano-CaCO₃/PP composites crystallized at higher temperature, the intensity of high-temperature melting peak was lower than that of low-temperature melting peak. The isothermal crystallization time had little effect on the melting temperatures. Translated from Acta Scientiarum Naturalium Universitatis Sunyatseni, 2006, 45(2): 41–45 [译自: 中山大学学报 (自然科学版)]     

Activity of horseradish peroxidase in aqueous and reverse micelles and back‐extraction from reverse‐micellar phases

Studies on the activity of the enzyme horseradish peroxidase (HRP) have been carried out in micellar as well as reverse‐micellar media. The activity of the enzyme was studied in the presence of different classes of surfactants – ionic as well as non‐ionic. In aqueous media, the activity of the enzyme varied depending on whether the concentration of the surfactant used was above or below the critical micellar concentration (CMC). The enzyme was also studied in reverse‐micellar systems. HRP was introduced into the reverse micellar phase by the injection method and its activity within the reverse micelles was determined. The effect of water to surfactant ratio (W_o) on activity within reverse micelles was studied, and an almost two‐fold increase in activity was seen when the enzyme was encapsulated within reverse micelles of aqueous phase fractional hold‐up (?) of 0.0072 (v/v) consisting of sodium bis‐(2‐ethylhexyl) sulfosuccinate (AOT) in isooctane at a W_o of 20. The activity of HRP was measured over a wide range of AOT concentrations having different W_o values. Back‐extraction of HRP from these reverse micelles was carried out at varying ionic strengths of phosphate buffer. Back extraction was found to be highest at pH 7.0 in 40 mol m^?3 phosphate buffer and 100 mol m^?3 sodium chloride. © 2001 Society of Chemical Industry     

反胶团在超临界CO_2萃取中的应用

近年来超临界流体萃取技术倍受人们青睐,超临界CO2作为有机溶剂的替代者促进了绿色工艺的发展。对于相对分子质量大的或亲水性分子及金属离子,CO2并不是一种好溶剂。采用反胶团体系可解决这一难题并开发许多新的工艺。本文概述了超临界CO2中反胶团技术的发展概况,重点阐述了反胶团在超临界CO2萃取中的应用。     

Solubility of CO2 in solid-state PET measured by pressure-decay method

The solubility of CO₂ in solid-state PET was measured using a pressure-decay method. In order to calculate the solubility of CO₂ in the amorphous region of PET, the crystallinity of solid state PET dissolved in CO₂ at different pressures and temperatures was measured by differential scanning calorimetry (DSC). The solubility increases with increasing pressure and it follows a linear relationship and obeys Henry’s law when the pressure is below 8 MPa. The effect of temperature on solubility is weak and the solubilities at different temperatures are almost the same under low pressures. At higher pressure, the solubility decreases with an increase in temperature. The solubility of CO₂ in the amorphous region of PET at 373.15 K, 398.15 K and 423.15 K was correlated with the Sanchez-Lacombe equation of state with a maximal correlation error of 6.69%. __________ Translated from Journal of East China University of Technology (Natural Science Edition), 2007, 33(4): 445–449 [译自: 华东理工大学学报(自然科学版)]     

Adsorption of Anionic–Cationic Surfactant Mixtures on Metal oxide Surfaces

This research evaluates the adsorption of anionic and cationic surfactant mixtures on charged metal oxide surfaces (i.e., alumina and silica). For an anionic-rich surfactant mixture below the CMC, the adsorption of anionic surfactant was found to substantially increase with the addition of low mole fractions of cationic surfactant. Two anionic surfactants (sodium dodecyl sulfate and sodium dihexyl sulfosuccinate) and two cationic surfactants (dodecyl pyridinium chloride and benzethonium chloride) were studied to evaluate the effect of surfactant tail branching. While cationic surfactants were observed to co-adsorb with anionic surfactants onto positively charged surfaces, the plateau level of anionic surfactant adsorption (i.e., at or above the CMC) did not change significantly for anionic–cationic surfactant mixtures. At the same time, the adsorption of anionic surfactants onto alumina was dramatically reduced when present in cationic-rich micelles and the adsorption of cationic surfactants on silica was substantially reduced in the presence of anionic-rich micelles. This demonstrates that mixed micelle formation can effectively reduce the activity of the highly adsorbing surfactant and thus inhibit the adsorption of the surfactant, especially when the highly adsorbing surfactant is present at a low mole fraction in the mixed surfactant system. Thus surfactant adsorption can be either enhanced or inhibited using mixed anionic–cationic surfactant systems by varying the concentration and composition.

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Reverse Micelle Supercritical Fluid Separations

Abstract

Initial results are presented showing the potential applications of reverse micelle supercritical fluid solvents in separation processes. The formation of reverse micelles in supercritical nalkane continuous phases is described. Phase diagrams obtained from view-cell studies of micellar and microemulsion phases formed in supercritical fluids are reported and shown to be strongly dependent on pressure. The solubility of AOT in ethane and propane over a range of pressures shows behavior typical of solids in supercritical fluids. The maximum water-to-surfactant ratio (W_O) increased dramatically in both ethane and propane systems as pressure was increased. At 300 bar W_O = 4 for ethane at 37 'C and W_O = 12 for propane at 103 _*C. The initial use of supercritical fluids containing reverse micelles for the extraction of solutes from an aqueous phase, and as mobile phases in chromatography, is described.     

单分散二氧化硅超细颗粒的制备

利用3种不同类型的表面活性剂反胶团体系制备SiO2超细颗粒,并与传统的Stober制备方法进行了对比. 在阴离子表面活性剂AOT和非离子表面活性剂TritonX-100两类体系中,得到了单分散的SiO2超细颗粒．在AOT体系中颗粒粒径随体系水含量w。的增大而增大;而TritonX-100体系中,颗粒粒径随w。的增大而减小;在阳离子表面活性剂(如CTAB,TOMAC)体系中无法得到SiO2超细颗粒．对不同体系所得颗粒的粒径标准偏差及粒度分布进行了对比,结果表明制备粒径小于100 nm的SiO2颗粒,反胶团法明显优于Stober方法,粒径相对标准偏差较低, 而对粒径大于100 nm的颗粒,Stober方法仍不失为一种很好的制备途径．     

Synthesis of macroporous poly(styrene-divinyl benzene) microspheres by surfactant reverse micelles swelling method

Macroporous poly(styrene-divinyl benzene) microspheres with pore size of about 500 nm were prepared by a new method, surfactant reverse micelles swelling method. The macroporous microspheres were prepared by convenient suspension polymerization. The difference from conventional suspension polymerization was that a higher concentration of surfactant was added in the oil phase. The effects of the amount and type of surfactants on the morphology of microspheres were investigated, and the formation mechanism was also discussed. Macropores were formed when the concentration of surfactant was much higher than critical micelle concentration (cmc). It was proposed that a large amount of reverse micelles formed by adding a large amount of surfactant in the oil droplet phase, and the reverse micelles could absorb water from the external aqueous phase. The water in the oil phase formed macropores after polymerization. The method developed in this study was convenient to prepare microspheres with larger pore size than the conventional method such as agglomeration method of nanoparticles.     

Synthesis and thermosensitive behavior of dextran graft copolymers containing poly(N-vinylcaprolactam) side chains

New graft copolymers were synthesized by grafting N-vinylcaprolactam onto dextran. Their composition and structure were investigated by elemental analyses, infrared spectra and thermogravimetric analyses. By optical transmittance measurements, it was found that the aqueous solutions of these graft copolymers showed a temperature-dependent transmittance change due to the introduction of thermosensitive poly(N-vinylcaprolactam) graft chains. Moreover, the lower critical solution temperature (LCST) of the graft copolymer in aqueous solution was dependent on its grafting extent and concentration. The LCST value was found to increase with the increase of the grafting extent and decrease with the increase of the copolymer concentration. With these stimuli-response properties, such polysaccharide derivative may hold potential applications in biomedicine and biotechnology. Translated from Acta Scientiarum Naturalium Universitatis Sunyatseni, 2006, 45(1): 50–52 [译自: 中山大学学报 (自然科学版)]     

Mixed micelles of some anionic-anionic, cationic-cationic, and ionic-nonionic surfactants in aqueous media

Critical micelle concentrations (CMC) were obtained from tensiometric studies on several binary surfactant mixtures (anionic-anionic, cationic-cationic, anionic-nonionic, and cationic-nonionic) in water at different mole fractions (0–1). The composition of mixed micelles and the interaction parameter β, evaluated from the CMC data for different systems using Rubingh's theory, are discussed. Marked interaction is observed for ionic-nonionic systems, whereas it is weak in the case of similarly charged surfactants. The influence of counterion valence in the formation of mixed micelles was investigated, and results suggest that in similarly charged surfactant mixtures, the degree of counterion binding does have a major role in deciding the extent of interactions. Salt addition reveals a weakening of interactions in ionic-nonionic systems, and this is attributed to head group charge neutralization and dehydration of the ethylene oxide units of the nonionic surfactants. Cloud point and viscosity data on these systems support the observation.     

超临界CO2体系中的反胶团

本文对超临界CO2反胶团技术的发展状况，包括基本原理，研究方法，应用领域，发展趋势和和了全面阐述。     

Microstructure of Triton X-100/poly (ethylene glycol) complex investigated by fluorescence resonance energy transfer

The microstructure of Triton X-100 (TX-100)/poly (ethylene glycol) (PEG) complex has been investigated by fluorescence resonance energy transfer (FRET), dynamic light scatter (DLS), freeze-fractured transmission electron microscopy (FF-TEM) and ¹H NMR technology. The nonionic surfactant TX-100 and pyrene are employed as energy donor and acceptor respectively, and the average distance between them is calculated quantitatively in the systems of TX-100/PEG with different molecular weights (MW). The results of FRET study indicate that the presence of PEG leads to the separation of donor and acceptor in TX-100 micelle, suggesting that PEG chains insert into TX-100 micelles making the microstructure of PEG-bound TX-100 aggregates looser than that of free micelles, which is independent of the MW of PEG. However, FF-TEM, DLS and ¹H NMR studies show that the morphology of TX-100/PEG complex depends on the MW of the polymer: PEG with shorter chain (MW < 2000 Da) insert into and wrap around TX-100 micelles and form sphere-like complex, while that with longer chain (MW > 2000 Da) would interact with numbers of TX-100 micelles and form coral-shaped clusters. In addition, the effects of temperature and alcohol on the microstructure of TX-100/PEG complex are studied.     

Mixed micelles of some metal dodecyl sulfates and triton X-100 in aqueous media

Tensiometric studies on several binary surfactant mixtures containing anionic surfactants, viz., metal (lithium, sodium, potassium, copper, cobalt, and magnesium) dodecyl sulfates and a nonionic surfactant (Triton X-100) in water at different mole fractions (0–1) provide critical micelle concentration (CMC) values. The composition of mixed micelles and the interaction parameter, β, evaluated from the CMC data for different systems using Rubingh's theory, are discussed. Marked interaction is observed with monovalent dodecyl sulfates. The influence of counter-ion valence on the formation of mixed micelles was investigated for anionic-nonionic systems, and results indicated that mixed systems with bivalent counter-ions in metal dodecyl sulfate resembled nonionic-nonionic systems where weak/negligible interaction has been reported. Salt addition revealed the weakening of interaction in the mixed systems, which is attributed to the head group charge neutralization and the dehydration of the ethylene oxide units of the nonionic surfactants. A few cloud point and viscosity data are also reported.     

Effect of inorganic electrolytes on dissolution behavior of mixed anionic-amphoteric surfactant systems

The effects of some inorganic electrolytes on the dissolution behavior of anionic-amphoteric mixed surfactant systems have been studied in terms of dissolution temperature of a hydrated solid surfactant; these systems are sodium dodecyl sulfate (SDS) - N^α,N^α-dimethyl-N^ɛ-lauroyl lysine (DMLL), including different inorganic electrolytes (NaCl, NaSCN, or CaCl₂). The dissolution temperatures of mixed surfactant systems are lower than those of pure surfactant solutions and become less than 0 C at a certain mole fraction of surfactants. As the concentration of NaCl increases, the dissolution temperatures of systems at a DMLL mole fraction lower than 0.4 increase, while those of systems at a ratio higher than 0.9 remain almost the same. With increasing concentration of NaSCN, the dissolution temperatures of systems at a DMLL mole fraction lower than 0.4 increase, while those of systems at a ratio higher than 0.9 decrease. For CaCl₂ systems, there exists a maximum in the dissolution temperature at a certain composition, because addition compound formation between anionic and zwitterionic surfactants occurs due to the presence of calcium ions.     

Effect of tartrazine dye on micellisation of cationic surfactants: conductometric,spectrophotometric, and tensiometric studies

The interactions between anionic dye (tartrazine) and cationic surfactants (dodecyltrimethylammonium bromide and cetyltrimethylammonium bromide) have been studied by conductometric, spectrophotometric, and tensiometric techniques. The conductance and surface tension of dodecyltrimethylammonium bromide and cetyltrimethylammonium bromide in pure water as well as in aqueous tartrazine when plotted with surfactant concentration gave values of the critical micelle concentration at different temperatures. As well as increasing the length of the carbon chain of surfactants, the presence of tartrazine reduces the critical micelle concentration. From specific conductivity data, the counterion dissociation constant, standard free energy, enthalpy, entropy of micellisation, surface excess concentration, surface tension at critical micelle concentration, minimum area per molecule, surface pressure at critical micelle concentration, and Gibbs energy of adsorption were evaluated. Spectroscopic studies reveal that the binding of dye to micelles brings a bathochromic shift in dye absorption spectra that indicates dye–surfactant interaction.