Suspension thiol-ene photopolymerization: Effect of stabilizing agents on particle size and stability

The impact of several surfactant species employed in the suspension photopolymerization of water-borne thiol-ene polymer microspheres is reported. The focus of analysis was on how different surfactant species and the surfactant concentrations affected particle size and particle size distributions. Surfactants used included sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), and hexadecyltrimethylammonium bromide (HTAB), Tween 20, Tween 40, Tween 60, Tween 80, Lutensol XL 70, Lutensol XP 70, Pluronic PE 6400, and Pluronic F108 Pastille. Using stabilizing agents or surfactants is necessary to prevent extensive aggregation and agglomeration of crosslinked thiol-ene polymer. All surfactants used in this study for particle stabilization and development produced spherical thiol-ene polymer particles. The chemical structure and concentration of the surfactants influenced the final particle size and size distribution of particles obtained. In general, it was found that smaller particles are obtained with higher concentrations of stabilizing agent, especially for ionic surfactants.     

On Plate Identification of Coexisting Polyoxyethylene (20) Stearyl Ether,Cetyl Pyridinium Chloride,Tetradecyl Trimethyl Ammonium Bromide and Polyoxyethylene (9.5) Octyl Phenyl Ether Surfactants with Preliminary Separation by Planar Chromatography

Separation studies of four surfactants (nonionic and cationic) were performed on silica high-performance thin-layer chromatographic plates with various solvent systems. The most useful chromatographic system for the mutual separation of coexisting polyoxyethylene (20) stearyl ether (C18EO20), cetylpyridinium chloride (CPC), tetradecyl trimethyl ammonium bromide (TTAB) and polyoxyethylene (9.5), octyl phenyl ether (OPEO9.5) was formamide + 1 M formic acid (50:50 v/v). The nature of ‘H’ and ‘H⁺’ of formic acid (H–COO⁻H⁺) on the mobility of these surfactants was studied. The interference due to the presence of metal cations as impurities on the resolution of mixture of C18EO20, CPC, TTAB and OPEO9.5 was also examined. The limits of detection of C18EO20, CPC, TTAB and OPEO9.5 estimated were 0.0620, 0.0310, 0.0625 and 0.0312 μg/zone, respectively. The practical applicability of the proposed method was tested for the identification of four coexisting surfactants after their separation from the spiked aqueous systems.     

Spectroscopic Investigation of the Interaction of BSA with Cationic Surfactants

The interactions between dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), cetyltrimethylammonium bromide (CTAB), and hexadecylpyridinium chloride (HDPC) with bovine serum albumin (BSA) in an aqueous solution (pH = 7.0, 0.001 M HEPES buffer) were studied by fluorescence and circular dichroism (CD) measurements. These categories of surfactants were used to elucidate the effect of hydrophilic group and length of hydrophobic chain surfactant on the mechanism of binding to BSA. The result revealed that for all surfactants, at low concentrations, the Stern‐Volmer plots have an upward curvature and in high concentrations, the quenching efficiency was decreased with increase in surfactant concentration. The activation energy of the interaction between cationic surfactants and BSA was measured. The results of CD show that the conformation of BSA has been changed in the presence of cationic surfactants.     

阴离子-阳离子-非离子三元复配型表面活性剂制备微乳化柴油

以磁力搅拌器为分散手段,油酸、十二烷基三甲基溴化铵(DTAB)或十四烷基三甲基溴化铵(TTAB)为主表面活性剂,在NH3.H2O存在的情况下,使用各种醇作助剂制备微乳化柴油,并对其增溶水量的各种影响因素进行研究。结果表明:复配体系TTAB/油酸/NH3.H2O比DTAB/油酸/NH3.H2O的增溶效果好,且在TTAB、油酸、NH3.H2O的摩尔比为1∶20∶17,复配乳化剂用量为3 g,正丁醇用量为3 mL,以0.15 mol/L的NaBr水溶液代替水相制备的微乳化柴油增溶水量最大、成本最低。所制备的微乳化柴油粒径在50～60 nm之间,稳定时间在190 d以上,黏度、密度、腐蚀性均符合国家标准。     

Radiation-induced admicellar polymerization of isoprene on silica: Effects of surfactant's chain length

This research compared radiation-induced admicellar polymerization with the traditional thermal process and studied the influence of the hydrocarbon chain length of different surfactants on film formation. Three types of surfactants were used in this study: dodecyl trimethyl ammonium bromide (DTAB), tetradecyl trimethyl ammonium bromide (TTAB) and cetyl trimethyl ammonium bromide (CTAB). Isoprene was used as a monomer for the formation of thin film inside the surfactant bilayers, called admicelle, adsorbed on silica surface. The results showed that an optimum dose can lead to a better film formation on silica, compared with the thermal method. However, when the dose was over the optimum value, the formation of polyisoprene film was diminished. The formation of polyisoprene film was found to depend not only on the hydrocarbon chain length of the surfactant, but also on the density of adsorbed surfactant on silica surface.     

The effect of cationic surfactants in acid cleaning solutions on protective performance and adhesion strength of the subsequent polyurethane coating

The subsequent effect of the use of monomeric cationic surfactants, dodecyltrimethylammonium bromide (DTAB) and its gemini counterpart, 12-4-12, in 1 M sulfamic acid cleaning solution on the corrosion resistance and adhesion strength of polyurethane coating on mild steel surface was studied by salt spray and pull off, respectively. The EIS (electrochemical impedance spectroscopy) was employed to evaluate the corrosion behavior of mild steel during the contact with sulfamic acid solutions. Inhibition performance of DTAB on mild steel at the initial period of immersion was somewhat higher than 12-4-12, while at prolonged immersion period 12-4-12 was more effective than DTAB. The higher protection and adhesion for the coating applied on the mild steel washed with DTAB solution was connected to more rapid adsorption for DTAB than 12-4-12 at short immersion period due to its small molecular weight which resulted in better mobility of DTAB molecules.     

Polymerization of vinyl acetate in microemulsions stabilized with dodecyltrimethylammonium bromide and cetyltrimethylammonium bromide

The polymerization of vinyl acetate in microemulsions stabilized with dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB) or mixture of these surfactants is examined. The polymerization rate diminishes as the surfactant mixture becomes richer in DTAB. Also, particles grow with conversion and become increasingly larger as the DTAB content in the mixture increases. Our results indicate that chain transfer reactions to monomer are more important than chain transfer reactions to polymer even at high conversions with CTAB. However, as the content of DTAB increases, bimolecular termination induced by coagulation, terminal double bond polymerization and chain transfer reactions to polymer become increasingly more important.     

Influence of ionic surfactants on the hydrogen peroxide bleaching of wool fabric

We have studied the influence of ionic surfactants on the bleaching of wool with hydrogen peroxide under acidic and alkaline conditions, comparing anionic sodium alkyl sulphates with eight, 12 and 16 carbon atoms and the cationic surfactant dodecyltrimethylammonium bromide (DTAB). Addition of ionic surfactants to both acidic and alkaline bleaching baths improved the whiteness of wool, especially at above 0.01 mol/l. Anionic surfactants prevented fibre damage during bleaching of wool, whereas DTAB accelerated it. The fibre damage decreased with increasing concentration of alkyl sulphates and with increasing length of hydrocarbon chain.     

Rheological Investigation of Wormlike Micelles Based on Gemini Surfactant in EG–Water Solution

The self‐assembly behavior of gemini surfactants in ethylene glycol (EG)‐water (5/95, v/v) mixed solvent was investigated by rheological measurements at 10 °C. The influence of molecular structure of the gemini surfactant and added hydrotrope on the solution properties was studied. Sodium salicylate (NaSal) showed stronger ability to induce 2‐hydroxyl‐propanediyl‐α,ω‐bis‐(dimethyldodecylammonium bromide), referred to as 12‐3(OH)‐12, to form wormlike micelles than sodium benzoate. Less NaSal is required to promote a sphere to rod transition and to reach the peak viscosity. Moreover, the concentrations of hydrotrope and gemini surfactant are both lower than conventional single‐chain surfactant systems to reach a comparable viscosity. The strong hydrophobicity of gemini surfactants and hydrotropes is responsible for the high efficiency in forming wormlike micelles in EG/water systems. The geometric structure of gemini surfactants also plays a vital role in self‐assembly into wormlike micelles. Dimethylene‐1,2‐bis‐(dodecyl dimethylammonium bromide), referred to as 12‐2‐12, shows absolute superiority over 12‐3(OH)‐12 in constructing wormlike micelles. The present study will be helpful for developing de‐icing fluids and anti‐freezing solutions, which need rheology control in EG‐aqueous medium at low temperature.     

阳-阴离子表面活性剂复配对褐煤疏水改性效果的研究

对不同配比下阳离子表面活性剂十二烷基三甲基溴化铵(DTAB)和阴离子表面活性剂十二烷基磺酸钠(SDS)复配溶液的性质进行了测量与计算,并测定了褐煤吸附复配表面活性剂后的润湿热值、水分复吸率值、红外光谱和Zeta电位值。结果表明:复配表面活性剂在降低表面张力的效能和效率方面均表现出协同作用,且通过润湿热值和水分复吸率值可以看出,对比单一表面活性剂,褐煤吸附复配表面活性剂后润湿热值与水分复吸率值都有明显的降低;通过红外光谱和Zeta电位值证明了复配表面活性剂对褐煤的作用效果和方式。表面活性剂复配体系相比相应的单一表面活性剂对于褐煤的疏水改性效果表现出明显的协同作用。     

己内酰胺在硫酸铵晶体表面吸附特性

引言 己内酰胺(caprolactam,CPL)受热时发生聚合反应,可作为尼龙-6纤维、工程塑料、聚酰胺等单体的原料,是一种重要的石油化工产品[1-2].硫酸铵是己内酰胺工艺的重要副产物,如意大利SNIA甲苯法工艺每生产1t己内酰胺副产硫酸铵约4.2 t[3].     

表面活性剂和四烷基溴化铵的复配 Ⅱ.四乙基溴化铵对离子型表面活性剂在气/液表面吸附行为的影响

用表面张力法研究了有机电解质四乙基溴化铵（（Ｅｔ）４ＮＢｒ）对离子型表面活性剂十二烷基硫酸钠（ＳＤＳ）和十二烷基三甲基溴化铵（ＤＴＡＢ）在气／液表面吸附行为的影响。表明（Ｅｔ）４ＮＢｒ提高了ＳＤＳ和ＤＴＡＢ降低水溶液表面张力的效率。但（Ｅｔ）４ＮＢｒ仅提高ＤＴＡＢ降低水溶液表面张力的能力,却反而削弱了ＳＤＳ降低水溶液表面张力的能力。通常电解质对离子表面活性剂表面吸附层的影响主要来自与表面活性离子电性相反的反离子,它们屏蔽了表面活性剂离子头基间的电荷,致使表面活性剂在气／液表面层排列紧密。有机电解质离子（Ｅｔ）４Ｎ＋作为反离子时,除了具有电解质离子的通常性能外,其乙基和表面活性剂碳氢链间还有一定程度的弱疏水相互作用,使部分（Ｅｔ）４Ｎ＋离子嵌入ＳＤＳ吸附层的离子头基区中,较大（Ｅｔ）４Ｎ＋离子的嵌入使周围的ＳＤＳ碳氢链排列疏松,改变了朝向空气面的表面碳氢链覆盖层结构,从而削弱了其降低表面张力的能力。     

DTAB表面活性剂在硅气凝胶干燥中的应用

使用十二烷基三甲基溴化铵（DTAB）阳离子表面活性剂溶液对湿凝胶进行处理,可降低凝胶中液体表面张力,从而得到保持较完整孔隙结构的硅气凝胶。结果表明,采用DTAB水溶液浸泡湿凝胶的方法要优于在凝胶形成前加入DTAB的方式。使用浓度为1.48×10-2 mol/L的DTAB水溶液浸泡湿凝胶可得到孔隙率为81.8%、平均孔径为15.749 nm、总孔体积为2.836 cm3/g、比表面积为923 m2/g的二氧化硅气凝胶;其吸脱附曲线明显高于其他添加浓度的吸脱附曲线,表明具有较高的吸附能力;在TEM图中可明显看出其具有孔隙结构。DTAB处理过的气凝胶明显优于未经处理的二氧化硅气凝胶。     

Effect of surfactants on phenol removal by the method of polymerization and precipitation catalysed by Coprinus cinereus peroxidase

The removal of phenol by peroxidase‐catalysed polymerization was examined using Coprinus cinereus peroxidase in the presence of surfactants. The non‐ionic surfactants with poly(oxyethene) residues, Triton X‐100, Triton X‐405 and Tween 20, enhanced the phenol removal efficiency at a level similar to high relative molecular mass poly(ethylene glycol) (relative molecular mass 3000). Although the improvement in the removal efficiency was less than that of Triton X‐100, Span 20, sodium lauryl sulfate (SDS) and lauryl trimethylammonium bromide (DTAB) also enhanced the removal efficiency. The requirement of the enzyme for almost 100% removal of 100 mg dm^?3 phenol decreased to one‐fourth by the addition of 30 mg dm^?3 Triton X‐100. Triton X‐100, Triton X‐405, Tween 20 and DTAB could reactivate the enzyme precipitated with the phenol polymer, leading to the restarting of the phenol removal reaction. Copyright © 2003 Society of Chemical Industry     

Effect of additives on the clouding behavior of sodium dodecyl sulfate + tetra-<Emphasis Type="Italic">n</Emphasis>-butylammonium bromide system

The effect of additives on the cloud point (CP) of nonionic surfactants has been studied for more than six decades. Ionic surfactants, however, generally do not show clouding. Recently, CP in ionic surfactant solutions have been reported in the presence of a few quaternary bromides. In this study, we report the effect of various additives (e.g., ureas, sugars, salts, organic solvents, acids) on the CP of sodium dodecyl sulfate (SDS) + tetra-n-butylammonium bromide (Bu₄NBr) systems. An increase in CP of the system with urea concentration is explained by its water structure-breaking ability. An opposite effect of thiourea may be due to the direct interaction of the compound with the SDS-Bu₄NBr mixed micelle. The CP-decreasing effect of sugars is due to their water structure-making ability. All the salts decrease the CP, owing to increased counterion binding. The organic solvents used here raise the CP, whereas the other organic additives decrease the CP. The overall criteria of CP variation seemingly depend upon the solubilities of the additive in the micellar interfacial region and the background solvent.     

Pd@Al2O3‐Catalyzed Hydrogenation of Allylbenzene to Propylbenzene in Methanol and Aqueous Micellar Solutions

The palladium on alumina (Pd@Al₂O₃)‐catalyzed hydrogenation of allylbenzene to propylbenzene was studied in methanol and aqueous micellar solutions of sodium dodecyl sulfate (SDS), decyltrimethylammonium bromide (DTAB), and t‐octylphenoxypolyethoxyethanol (TX‐100). Over Pd@Al₂O₃, propylbenzene was obtained via direct hydrogenation of allylbenzene and isomerization to β‐methylstyrene which was hydrogenated afterwards. In aqueous micellar solutions, the reaction was faster than in pure water, but slower than in methanol due to lower hydrogen solubility. In the H₂O/SDS system, a higher activation energy was obtained than in methanol. For the investigated surfactants, the initial reaction rate in the micellar systems decreased in the order SDS > TX‐100 > DTAB.     

离子型表面活性剂与牛血清白蛋白作用的比较研究

采用荧光光谱、紫外吸收光谱、动态光散射和Zeta电位法对比研究了十二烷基硫酸钠(SDS)和十二烷基三甲基溴化铵(DTAB)与牛血清白蛋白(BSA)的相互作用机理。结果表明：SDS和DTAB均能猝灭BSA内源荧光,298 K时的猝灭常数Ksv分别为2.64×104和304.21 L/mol。同步荧光光谱和三维荧光光谱显示SDS和DTAB对BSA的构象产生了影响。SDS对BSA荧光猝灭机理为动静联合猝灭机制;热力学计算表明,SDS与BSA的结合过程中,静电力起主导作用,并且能与BSA形成SDS/BSA超分子复合物;DTAB对BSA荧光猝灭机理为动态猝灭,作用力主要是疏水作用。SDS和DTAB与BSA的平均结合距离分别为2.77和4.73 nm。综合结合常数、粒径和Zeta电位等变化,在相同条件下具有较大电荷密度和较小体积极性头基的SDS与BSA具有更强的结合作用。     

PITTING CORROSION OF SAF2205 DUPLEX STAINLESS STEEL IN ACETIC ACID CONTAINING BROMIDE AND CHLORIDE

Development of duplex stainless steels has been linked strongly with the increasing requirements of the industry for resistance of materials to highly aggressive environments. In the present work, the effects of bromide and chloride ion concentrations and temperature on the pitting corrosion of commercial grade SAF2205 duplex stainless steel were studied. Cyclic polarization and scanning electron microscopy (SEM) techniques were used to study the pitting corrosion behavior of this steel in 80%v/v acetic acid solution containing 0.01, 0.1, 0.2, and 0.5 M sodium bromide and sodium chloride, respectively. Pitting potential was found to decrease with the increase of the temperature and bromide ion concentration. In the presence of chloride ions, pitting corrosion was not observed at room temperature. Critical pitting temperature in chloride-containing solutions was estimated to be above 35°C. In the case of pitting, SEM observation revealed that pit initiation is in the austenite phase regions.     

溴化铜对乙酰基愈创木酚的选择性溴化反应

以愈创木酚为起始物,合成了4-乙酰基愈创木酚,然后以4-乙酰基愈创木酚和溴化铜(CuBr2)为反应物,分别用乙酸乙酯与三氯甲烷的混合溶液、甲醇、乙醇作为反应溶剂合成了4-(α-溴代乙酰基)-愈创木酚,并利用红外光谱、核磁共振谱(1H-NMR)等手段对其化学结构进行了分析和确认。研究结果表明,利用甲醇和乙醇作为反应溶剂,将该4-乙酰基愈创木酚的取代反应由非均相转变为均相,得率稳定在90%以上。该溴代反应受反应时间的影响不大。重结晶的方法不能将产物分离,采用硅胶层析用乙酸乙酯和正己烷(1∶2,V/V)作为流动相可分离得到产物。     

Fast and very slow reactions: phase transfer catalysis

The effect of phase transfer catalysts (PTC), such as tricaprylmethyl ammonium chloride (Aliquat-336), cetyl trimethyl ammonium bromide, etc. on the rate of alkaline hydrolysis of different formate and acetate esters was studied. In the case of formate esters extraction is accompanied by fast pseudo-first order reaction in diffusion film; for acetate esters the reaction is insufficiently fast to occur in the diffusion film.The values of the volumetric rate of extraction, R_Aa, and the specific rate of extraction, R_A, with or without PTC, were measured in a fully baffled mechanically agitated contactor and a constant interfacial area stirred cell, respectively. The alkaline hydrolysis reaction was carried out with aqueous solutions of sodium hydroxide or aqueous lime slurry and the effect of speed of agitation and PTC concentration on the rate of hydrolysis was studied. A remarkable increase in the value of R_A was realized in the presence of PTC and the enhancement factor for the formate ester hydrolysis reaction ranged from 20 to over 200.