Influence of Cationic Surfactants on the Crystallization of Cis‐ and Trans‐Isomers

The crystals of cis‐ and trans‐isomers present in principle similar chemical groups on their respective crystal faces. Here, the crystallization of cis‐ and trans‐isomers (maleic acid and fumaric acid) in an aqueous solution containing cationic surfactants with different hydrophobic chains (the long hydrophobic chains of dodecyltrimethylammonium bromide < cetyltrimethylammonium bromide < trimethylstearylammonium bromide) was investigated. Results showed that the surfactants presented different effects on the crystallization of cis‐ and trans‐isomers. For trans‐isomers (fumaric acid), the surfactants with longer hydrophobic chains or higher solution concentrations will favor a wider metastable zone width (MZW) and a greater morphology change. By contrast, both the MZW and morphology development of cis‐isomers (maleic acid) were not affected by these surfactants. The chemical groups on crystal faces, surface grooves, and molecular polarity were compared to reveal the different influences of surfactants on the crystallization of cis‐ and trans‐isomers.     

Interaction of antipsychotic drug with novel surfactants: Micellization and binding studies

The interaction of cationic gemini surfactants(alkanediyl-α,ω-bis(alkyl dimethylammonium bromide)) with an antipsychotic drug(chlorpromazine hydrochloride(CPZ)) has been investigated. Various micellar and interfacial parameters have been deliberated by surface tension measurement to report the nature of interactions between drug and novel surfactant mixtures. The behavior of mixed systems, their compositions and activities of components have been analyzed in the light of Rubingh's theory. The results indicate synergism in the binary mixtures.The binding study between CPZ and surfactants has been done by spectroscopic techniques such as UV–visible and fluorescence. The results are discussed in the light of the use of gemini surfactants as promising drug delivery agents for phenothiazine drugs, and hence, improve their bioavailability.     

Micellization Studies of Dicationic Gemini Surfactants (m-2-m Type) in the Presence of Various Counter- and Co-Ions

Salts have the ability to influence the water activity and self-association of ionic micelles. In the present case, gemini surfactants; ethanediyl-α,ω-bis(dimethyl alkyl ammonium bromide) (referred to as m-2-m, m = 10, 12, 14) are synthesized and their micellization study in aqueous medium in presence of monovalent inorganic (NaBr, NaNO₃, NaCl, KCl, LiCl) and organic salts (NaTos, NaBenz, NaSal) at 303 K is systematically investigated by conductometric and tensiometric methods. All the salts have the tendency to lower the critical micelle concentration of the surfactants. The effect of inorganic salts on the micellization properties has been found to obey the Hofmeister series. Organic salts reduce the CMC more effectively as compared to inorganic salts. The theoretical models of Rubingh and Rosen have been used to compare the results and obtain the interaction parameters, minimum area per molecule, surface excess, mixed micelle composition, activity coefficients and free energies of micellization/adsorption.     

脂肪酸双酯双磺酸盐型双子表面活性剂的合成及性能

以脂肪酸、二甘醇、氯磺酸为原料,经酯化、磺化反应制备了4种二甘醇双(α-磺酸钠)烷基羧酸酯表面活性剂。用红外光谱、元素分析对产物进行了表征,并对其表面活性和聚集行为进行了研究。结果表明,该类脂肪酸双酯双磺酸盐型双子表面活性剂比十二烷基硫酸钠的临界胶束浓度低1～2个数量级和更强的降低表面张力的能力。稳态荧光猝灭实验表明,表面活性剂胶束聚集数随着烷烃链碳原子数的增加而逐渐减小。     

Synthesis of polymer‐supported quaternary ammonium salts and their phase‐transfer catalytic activity in halogen‐exchange reactions

Polymer‐supported quaternary ammonium salts were prepared, and their applications as phase‐transfer catalysts in aqueous organic systems were investigated. The polymer‐bound phase‐transfer catalysts were prepared with polystyrene resins crosslinked with the bifunctional monomers divinylbenzene and 1,4‐butanediol dimethacrylate. The polymers were functionalized with chloromethyl groups and quaternized with trialkylamines having different alkyl chains. The obtained phase‐transfer catalysts were characterized with IR spectroscopy and elemental analysis. The thermal stability was also determined by the thermogravimetric method. The catalytic properties of the phase‐transfer catalysts were studied in halogen‐exchange reactions. The effects of the nature and extent of crosslinking of the polymer support, the alkyl groups of the trialkylamine, and the reaction conditions were investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci 2009     

3,5‐Bis(n‐perfluorooctyl)benzyltriethylammonium Bromide (F‐TEBA): An Efficient,Easily Recoverable Fluorous Catalyst for Solid‐Liquid PTC Reactions

A readily available 3,5‐bis(perfluorooctyl)benzyl bromide and triethylamine were reacted under mild conditions to give 3,5‐bis(n‐perfluorooctyl)benzyltriethylammonium bromide ( F‐TEBA ), an analogue of the versatile phase‐transfer catalyst, benzyltriethylammonium chloride (TEBA), containing two fluorous ponytails. This perfluoroalkylated quaternary ammonium salt was successfully employed as a catalyst in a variety of reactions run under solid‐liquid phase‐transfer catalysis (SL‐PTC) conditions. Thus, being both hydrophobic and lipophobic, F‐TEBA could be quickly recovered in quantitative yields, and reused without loss of activity over several reaction cycles.     

Polymer‐Cationic Surfactant Interaction: 1. Surface and Physicochemical Properties of Polyvinyl Alcohol (PVA)‐S‐Alkyl Isothiouronium Bromide Surfactant Mixed Systems

Surface properties of polyvinyl alcohol (nonionic polymer) and three synthesized cationic surfactants, namely, S‐alkyl isothiouronium bromide at different mole fractions of 1:9, 3:7, 5:5, 7:3, and 9:1, were investigated. The values of the surface parameters were discussed according to the type of interaction between the cationic surfactant and type of polymer studied. The S‐alkyl isothiouronium bromide surfactant molecules are positively charged molecules, and the PVA chains contain hydroxyl groups that are partially negatively charged centers. The comparison between the surface properties of the individual cationic surfactants and their mixture with PVA polymer showed that the mixed systems have some advantages over the individual cationic surfactants.     

Formation of a Third Liquid Phase and Its Reuse for Dibenzyl Ether Synthesis in a Tetraalkylammonium Salt Phase Transfer Catalytic System

This paper describes the formation of a third liquid phase in a phase transfer catalytic system in the presence of benzyl alcohol and potassium hydroxide, where dodecane and tetraalkylammonium bromide serve as organic solvent and catalyst, respectively. In this kind of system, a symmetrical ether (dibenzyl ether) was synthesized from benzyl chloride and benzyl alcohol at 323 K. In particular, the investigation demonstrates that the observed reaction rate constant depends on the length of the alkyl group of the catalyst. Tetrabutylammonium bromide exhibits the highest catalytic activity among the catalysts explored. With respect to the reuse of the third liquid phase, the results confirm that there is no decrease in phase transfer catalytic activity in three consecutive runs.     

Characterization of monomeric and gemini cationic amphiphilic molecules by fluorescence intensity and anisotropy. Part 2

Four fluorophores of different nature, structure and properties were employed as probes for the characterization of a series of alkanediyl-α,ω-bis(alkyldimethyl ammonium bromide) surfactants. Pyrene and 3-(2-Benzothiazolyl)-7-(diethylamino)coumarin (coumarin 6) fluorescence intensity as well as coumarin 6 and fluorescein sodium salt fluorescence anisotropy were used to determine cmc whilst coumarin 6, fluorescein sodium salt and perylene fluorescence anisotropy was exploited to provide information on micellar structure; cmc values were confirmed using conductivity measurements. Conductivity data were analysed by means of a method which reveals the formation of ion pairs or premicellar aggregates; this approach was useful to justify and confirm results obtained using fluorescence.     

Synthesis and Evaluation of Bis-quaternary-Based Surfactants as Additives for Water-Based Mud

Two series of cationic gemini surfactants, alkanediyl-α,ω-bis[N,N-dimethyl alkyl (octyl or dodecyl)ammonium] dibromide (R-s-R; s = 6, 10, 12 and R = 8 and 12) were prepared and evaluated as additives for water-based mud. The chemical structures of the prepared surfactants were confirmed using FTIR and mass spectroscopy. Surface activity of these compounds has been studied and their surface properties including surface tension, emulsification power, critical micelle concentration, effectiveness, maximum surface excess and minimum surface area were determined. The results showed that the prepared compounds have significant surface activity, especially those of longer hydrophobic chain length. The prepared cationic gemini surfactants were evaluated as viscosifiers and filter loss additives for water-based mud formulated from local Na-montmorillonite clay. XRD analysis was carried out to the Na-montmorillonite clay to determine the interaction of the surfactants with inter layers of the clay structure. Rheological properties, gel strength, thixotropy, filtration properties and the effect of temperature on rheological properties of the water-based mud were studied. The results indicated that the gemini surfactants have a positive effect on the rheological and filtration properties of the Na-montmorillonite clay according to American Petroleum Institute specifications.     

Glucamine-based gemini surfactants I: Gemini surfactants from long-chain <Emphasis Type="Italic">N</Emphasis>-alkyl glucamines and α,ω-diepoxides

N-Alkyl glucamines can be reacted with α,ω-diepoxides to yield gemini (dimeric) surfactants similarly to the reaction of glucamine with terminal epoxides. Under the conditions chosen for this work, epoxides were quantitatively converted in the presence of an equimolar amount of amine to gemini surfactants. Reactions could be carried out under mild conditions (70°C) in methanol, and products were obtained quantitatively by removing the solvent. The combination of N-octyl glucamine, N-decyl glucamine, or N-dodecyl glucamine with diepoxides of α,ω-diolefins having chain lengths of C₈, C₉, C₁₀, or C₁₄ resulted in gemini surfactants differing in spacer length and length of hydrophobic alkyl chains. Surface-active properties were studied by measuring surface tension and evaluating foaming properties. Tensiometric studies showed the reduction of surface tension down to 29–33 mN/m and critical micelle concentrations often in the range of 3–150 mg/L. Comparison of a selected gemini surfactant [1,8-bis(N-dodecyl glucamino-2,7-octane diol] with its corresponding “single surfactant” demonstrated the enhancement of surface-active properties afforded by the gemini structure.     

Polymerization by phase transfer catalysis

Summary Poly(amido-carbonate)s and poly(amido-thiocarbonate)s derived from 1,6-bis(4-hydroxyphenyl-carbamoyl)-hexamethylene I and 1,4-bis(4-hydroxyphenyl-carbamoyl)-phenylene II, and phosgene or thiophosgene, have been synthesized by a phase transfer catalysis process, which was ineffective for polymers derived from monomer I because the best results were obtained without catalyst, but was effective for those derived from monomer II obtaining higher yields when the catalysts were used. The ineffectivity was attributed to a hydrolytic process of the polymeric chains in the reaction media.     

9,9-双（甲氧基甲基）芴的合成及其应用研究

9,9-双（甲氧基甲基）芴（BMMF）的合成分两步进行：首先,在乙醇钠催化剂的作用下,芴与多聚甲醛反应合成了中间体9,9-双（羟甲基）芴（BHMF）,然后以四丁基溴化铵（TBAB）为相转移催化剂,再与氯甲烷发生烷基化反应合成了9,9-双甲氧基甲基芴。用9,9-双（羟甲基）芴作外给电子体进行了丙烯聚合应用,实验结果表明：9,9-双（甲氧甲基）芴（BMMF）是聚丙烯Ziegler-Natta催化体系较好的外给电子体。     

Biphasic and Flow Systems Involving Water or Supercritical Fluids

Two processes are described for improving reaction rates for relatively hydrophobic substrates in aqueous biphasic systems. In the first, 1-octyl-3-methylimidazolium bromide ([Octmim]Br) increases the rate of hydroformylation of 1-octene from 8% conversion in 24 h to full conversion of 1.5 h. Phase separation is fast and catalyst retention is good. 1-Hexyl-3-methylimidazolium bromide gives little rate enhancement, whilst 1-decyl-3-methylimidazolium bromide gives stable emulsions., The mechanism of action of these additives is discussed. In the second approach, functionalising PPh₃ with amidine groups allows the rhodium catalysed hydroformylation of 1-octene in toluene with a very high reaction rate. The catalyst can be switched between toluene and water by bubbling CO₂ and back into toluene by bubbling N₂ at 60 °C. This switching has been used to separate the catalyst from hydrophobic (from 1-octene) or hydrophilic (from allyl alcohol) aldehydes obtained from hydroformylation reactions. CO₂ expanded liquids have been shown to be effective media for transporting substrates and catalysts over supported ionic liquid phase (SILP) catalysts. The advantages offered over all gas phase and liquid phase catalysts are discussed.     

Polymer–surfactant interactions in graft copolymer solutions

Graft copolymers composed of water-soluble cellulosic backbones and > 0.4% (by weight) alkyl grafts are insoluble in water but soluble in surfactant solutions. Studies of the bulk viscosity and stability of polymer-surfactant solutions at 49°C indicate that the mechanism for solubilization of the polymer is the incorporation of the alkyl side chains into surfactant micelles. The tendency for side chains to combine with micelles appears to depend at least in part on the geometry of the surfactant tail group such that surfactants containing straight-chain tail groups solubilize alkyl side chains more readily than olefinic surfactants. The presence of small solutes near the surface of the micelle also inhibits incorporation of side chains from the polymer. Unsolubilized side chains remain in the aqueous phase of the solution, where they form thermally unstable intermolecular aggregates.     

9,9-双甲氧甲基芴的合成及其光谱分析

以芴为原料,在乙醇钠的催化下,经多聚甲醛羟甲基化反应合成了中间体9,9-双羟甲基芴,然后以四丁基溴化铵为相转移催化剂,再与氢氧化钠、碳酸二甲酯发生烷基化反应,合成了目标化合物。通过紫外光谱、红外光谱和核磁共振谱等分析测试手段对中间体和目标产物进行了结构表征并逐一归属。     

Mixed Micellar and Interfacial Interactions of a Triblock Polymer (EO37PO56EO37) with a Series of Monomeric and Dimeric Surfactants

The mixed micellar and interfacial properties of mixtures of triblock polymer (TBP) with a series of monomeric (dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and cetyltrimethylammonium bromide, and dimeric (dimethylene bis[alkyldimethylammonium bromide], m-2-m, where m = 10, 12, and 14) cationic surfactants were investigated using surface tension and viscosity measurements in aqueous solutions at different temperatures. Various physicochemical properties such as critical micelle concentration, mixed micellar mole fraction, interaction parameter, interfacial, and thermodynamic parameters were evaluated. All the binary mixtures exhibit synergistic interactions which increase with temperature and pass through a minimum with the increase in hydrophobic chain length of the cationic surfactants. The contribution of TBP in mixed micelle formation also increases with the hydrophobic chain length of the surfactants. The interfacial and thermodynamic parameters reveal that the adsorption of the surfactant mixtures at the air–solution interface is more favorable than that of micelle formation and the unfavorable enthalpy changes are overwhelmed by favorable entropy changes. Further, the mixtures of TBP with smaller chain length surfactants show a sharp rise in relative viscosity at higher mole fractions of these surfactants.     

烷基芳烃催化加氢脱烷基催化剂研究进展

综述了烷基芳烃催化脱烷基催化剂和反应机理的最新进展。脱烷基催化剂包括金属催化剂、金属氧化物催化剂和分子筛催化剂。烷基侧链不同,其脱除速率不同。在金属活性中心上,烷基芳烃遵循吸附脱氢的反应机理;在酸性中心上可能遵循H转移、链式正碳离子以及自由基机理。对芳烃催化脱烷基的应用前景进行了展望。     

相转移催化合成邻硝基苯乙醚的研究

以邻硝基氯苯、氢氧化钠、乙醇为原料,在相转移催化剂的条件下合成了邻硝基苯乙醚。采用了各种不同的相转移催化剂,主要包括季铵盐、聚乙二醇(PEG)及季铵盐与聚乙二醇两者的复配,对比考察了催化剂种类和用量对邻硝基苯乙醚反应收率的影响,确定了最佳催化剂及反应工艺条件,并且在搅拌器型式上进行了改进。实验结果表明,四丁基溴化铵具有最佳催化活性,邻硝基苯乙醚的收率为82.8%,色谱纯度为99.0%。     

Photopolymerization and characteristics of reactive organoclay–polyurethane nanocomposites

Polymerizable ammonium surfactants with two methacrylate alkyl chains were successfully synthesized via Michael‐Addition and quaternization reaction. Organoclays containing reactive methacrylate groups were prepared by cationic exchange process. Intercalated nanocomposites have been produced by UV initiated polymerization with different organophilic clay loading. X‐ray diffraction (XRD) spectroscopy showed that the d spacing of organoclay increased with increment of methacrylate alkyl chains length. When organoclay were dispersed in urethane acrylate resin, and photopolymerized, the d spacing increased, but the increasing extent decreased with increment of the methacrylate alky chains length. Thermogravimetric analysis indicated that incorporation of reactive organoclay had better thermal stablity than cetyltrimethylammonium bromide (CTMA)‐modified organoclay and dynamic mechanical analysis (DMA) showed nanocomposites containing reactive organoclay had high glass transition temperature and storage modulus. Tensile analysis implied that incorporation of reactive organoclay could enhance mechanical and tensile properties dramatically. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers