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Ionic Surfactants (ionic + surfactant)
Selected AbstractsControlled, radical reversible addition,fragmentation chain-transfer polymerization in high-surfactant-concentration ionic miniemulsionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2004J. B. McLeary Abstract Living free-radical polymerization of methacrylate and styrenic monomers with ionic surfactants was carried out with reversible addition,fragmentation chain transfer in miniemulsion with different surfactant types and concentrations. The previously reported problem of phase separation was found to be insignificant at higher surfactant concentrations, and control of the molar mass and polydispersity index was superior to that of published miniemulsion systems. Cationic and anionic surfactants were used to examine the validity of the argument that ionic surfactants interfere with transfer agents. Ionic surfactants were suitable for miniemulsion polymerization under certain conditions. The colloidal stability of the miniemulsions was consistent with the predictions of a specific model. The living character of the polymer that comprised the latex material was shown by its transformation into block copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 960,974, 2004 [source] Synthesis of ZnO whiskers with different aspect ratios by a facile solution routePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2008Juan Xie Abstract Monodispersed zinc oxide (ZnO) whiskers with different aspect ratios were successfully prepared via a simple solution route at low temperature. It is found that the diameter and aspect ratio of ZnO whiskers depend critically on the structure and type of ionic surfactant added in the reaction solution. To further understand the effect of the surfactants on the formation process of ZnO whiskers, concentration measurements of Zn(II) remaining in the solution as well as scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) analyses of the solid product have been made at regular intervals throughout the reaction with and without the surfactants. A possible formation process has been reasonably suggested based on these systematic experimental results. It is believed that anion surfactants are capable of slowing down the nucleation and growth rate of ZnO crystallite, which is favorable for the anisotropic growth habit of ZnO crystal to form needle-like whiskers. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] SN2 Displacement by Bromide Ions in Dichloromethane , The Role of Reverse MicellesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2006Lucia Brinchi Abstract Reverse micellar systems are of interest as reaction media because they are powerful models for biological compartmentalization, enzymatic catalysis and separation of biomolecules. Solutions of ionic surfactants in apolar solvents may contain reverse micelles, but they may also contain ion pairs, or small clusters, with waters of hydration. We studied the bimolecular reaction in CH2Cl2 solutions of cationic tetraalkylammonium bromide salts (onium salts), such as cetyltrimethylammonium bromide (CTABr), cetyltripropylammonium bromide (CTPABr) and tetra- n -butylammonium bromide (TBABr). Methylnaphthalene-2-sulfonate (,-MeONs), its 6-sulfonate derivative (,-MeONsS,) as the 2,6-lutidinium salt and methyl-5- N,N,N,trimethylammonium naphthalene-1-sulfonate (,-MeONsNT+) as the trifluoromethanesulfonate salt react with Br, in CH2Cl2. First-order rate constants, kobs, increase linearly and similarly for the three substrates with increasing concentrations of the onium salts. Reactions are faster with TBABr than they are with CTPABr and CTABr, and the reactivity of the three substrates is in the order: ,-MeONsNT+ >> ,-MeONsS, > ,-MeONs. The reactions are inhibited by the addition of H2O, but CTABr tolerates H2O in large excess. At [H2O]/[CTABr] = w0 , 6, "water-pool" reverse micelles form, and kobs for all three substrates is then independent of w0. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Influence of cosurfactant in microemulsion systems for color removal from textile wastewaterJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2005Leocadia Terezinha Cordeiro Beltrame Abstract Microemulsion systems have proved very efficient in color removal from textile wastewater using n -butyl alcohol as cosurfactant. The cosurfactant has a very important role in microemulsified systems, as it is responsible for their stability, mainly in systems formed by ionic surfactants. Although very efficient, n -butyl alcohol is partially soluble in water, which would permit its passage to the effluent. In this work, isoamyl and octyl alcohols, due to their lower solubility in water, were used as cosurfactants to evaluate their influence in color removal. The colorimetry system used was the CIE L*a*b* (CIELAB) color space and CIE L*a*b* color difference (,E*ab). The wastewater used in this study was the reactive exhausted dye liquor from a dye house (first discharge) containing Procion Yellow H-E4R (CI Reactive Yellow 84), Procion Blue H-ERD (CI Reactive Blue 160) and Procion Red H-E3B (CI Reactive Red 120). The obtained results were modeled using an experimental planning (the Scheffé net) and evaluated through isoresponse diagrams by correlation graphs between experimental values and those obtained by the models with an error lower than 4%. All the optimized systems were very efficient and more than 94% of the dyes contained in the effluent were removed. The microemulsion load capacity was determined using a synthetic solution containing, the same dyes present in the reactive exhausted dyebath, but 200 times concentrated, and the dyes extraction was more than 99.6%. By comparing n -butyl, isoamyl and octyl alcohols, it was observed that the system using isoamyl alcohol presented slightly better color removal and much higher load capacity than the n -butyl and octyl alcohols. Copyright © 2004 Society of Chemical Industry [source] Controlled, radical reversible addition,fragmentation chain-transfer polymerization in high-surfactant-concentration ionic miniemulsionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2004J. B. McLeary Abstract Living free-radical polymerization of methacrylate and styrenic monomers with ionic surfactants was carried out with reversible addition,fragmentation chain transfer in miniemulsion with different surfactant types and concentrations. The previously reported problem of phase separation was found to be insignificant at higher surfactant concentrations, and control of the molar mass and polydispersity index was superior to that of published miniemulsion systems. Cationic and anionic surfactants were used to examine the validity of the argument that ionic surfactants interfere with transfer agents. Ionic surfactants were suitable for miniemulsion polymerization under certain conditions. The colloidal stability of the miniemulsions was consistent with the predictions of a specific model. The living character of the polymer that comprised the latex material was shown by its transformation into block copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 960,974, 2004 [source] Effect of surfactant type on the synthesis of PMMA using redox initiation and high frequency ultrasoundPOLYMER ENGINEERING & SCIENCE, Issue 10 2008Cristina Parra In the present work, a study of the effect of the surfactant nature on the synthesis of polymethylmethacrylate (PMMA) obtained by high frequency ultrasonic radiation and redox initiation is presented. The surfactants used were an anionic: sodium lauryl sulfate (SLS) and a nonionic: nonylphenol etoxilated. Different morphologies, particle size, and microstructures were obtained depending on the surfactant concentration (0.5, 1.0, 1.5, and 2.0)%. The highest conversion values of PMMA were obtained with SLS, resulting in a highly syndiotactic polymer. High frequency ultrasound is very efficient when ionic surfactants are used. However, for nonionic surfactants ultrasonic irradiation is very inefficient to initiate polymerization, in this case the effect of redox initiation was very marked increasing polymerization conversion. For this, surfactant blends of PMMA/PEO were obtained when redox initiation was used together with high frequency ultrasound. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers. [source] A simple automated method of quantitative characterization of foam behaviour,POLYMER INTERNATIONAL, Issue 4 2003Dr Klaus Lunkenheimer Abstract There are various methods available to measure foam stability. However, their main drawback is that their results are hardly comparable because definite boundary conditions are missing. One particular disadvantage is that there is no method which is applicable to systems of very low (transient or ,wet' foams) as well as of very high (metastable or ,dry' foams) foam stability. Here, we put forward a novel automatic, pneumatic method that is applicable to both systems. Its principle relies on the measurement of the foam produced by dispersing a definite amount of gas in a definite volume of solution at constant gas velocity. Foam and draining solution are determined simultaneously. This method has advantages over all other methods in several respects such as: (1) it represents a simple and definite procedure under well-defined boundary conditions, (2) it is generally applicable to all kinds of foam, and (3) it provides new standard parameters for the quantitative characterization of foamability and foam stability. The standard parameters can be related to the basic adsorption properties and the structure of the surfactant. The method's capability is demonstrated with three different non-ionic and ionic surfactants belonging to the wet (n-octanoic acid) and dry foam systems (n-nonyl-,- D -glucopyranoside and sodium dodecylsulfate). Copyright © 2003 Society of Chemical Industry [source] Protein Refolding Mediated by Reverse Micelles of Cibacron Blue F-3GA Modified Nonionic SurfactantBIOTECHNOLOGY PROGRESS, Issue 2 2006Xiao-Yue Wu An affinity-based reverse micellar system formulated with nonionic surfactant was applied to the refolding of denatured-reduced lysozyme. The nonionic surfactant of sorbitan trioleate (Span 85) was modified with Cibacron Blue F-3GA (CB) as an affinity surfactant (CB-Span 85) to form affinity-based reverse micelles in n -hexane. The water content of 15 was found optimal for lysozyme refolding in the reverse micellar system of 62.7 mmol/L Span 85 with coupled CB of 0.3 and 0.5 mmol/L. In addition, the operating conditions such as pH and the concentrations of urea and redox reagents were optimized. Under the optimized conditions, complete renaturation of lysozyme at 3,3.5 mg/mL was achieved, whereas dilution refolding in the bulk aqueous phase under the same conditions gave much lower activity recovery. Moreover, the secondary structure of the refolded lysozyme was found to be the same as the native lysozyme. Over 95% of the refolded lysozyme was recovered from CB-Span 85 reverse micelles by a stripping solution of 0.5 mol/L MgCl2. Thus, the present system is advantageous over the conventional reverse micellar system formed with ionic surfactants in the ease of protein recovery. [source] Water Soluble Cruciforms: Effect of Surfactants on FluorescenceCHEMISTRY - AN ASIAN JOURNAL, Issue 2 2009Juan Tolosa Dr. Abstract Brighten up! Adding surfactants to aqueous solutions of three different water-soluble cruciforms (XF) improves their fluorescence quantum yields. Additionally, changes are observed in the emission wavelength of the XF around the critical micelle concentration (cmc) of the surfactant. Three 1,4-bis-(aminostyryl)-2,5-bis(phenylethynyl) benzenes carrying four, six, or eight acetic acid units were investigated for their surfactochromicity. Anionic, cationic, and nonionic surfactants as well as a surfactant-like protein (bovine serum albumin, BSA) were added to buffered solutions of the XFs in water, causing,in most cases,the fluorescence quantum yield to increase significantly and a blue- or red-shifted emission to be observed. The addition of cationic (cetyltrimethylammonium bromide, CTAB) and neutral (Brij 35, TWEEN 20 and Triton X-100) surfactants to XFs causes a red shift in their emission at low or very low surfactant concentrations that we attribute to surfactant-induced excimer formation. The fluorescence quantum yield is in most cases a monotonous function of surfactant concentration. For the investigated ionic surfactants, the fluorescence quantum yield of the XFs does not change much after the critical micelle concentration (CMC) of the surface is reached. However, in the case of non-ionic surfactants, the fluorescence quantum yields of the XFs starts to increase after the CMC has been reached, suggesting that different effects are involved. [source] | |||||||||||||