Effect of surfactant structure on catalysis of microemulsion for photoisomerization of trans-stilbene

In this study,the photoisomerization of trans-sfilbene was carried out in water in oil (W/O) microemulsions by using sodium dodecyl sulfate (SDS),dodecyl trimethyl ammonium bromide (DTAB) and cetyl trimethyl ammonium bromide (CTAB) as surfactant,respectively.The catalytic effect of microemulsion on this reaction is closely related to the structure of surfactant.When there is no photosensitizer 9,10-dicyanoanthracene (DCA),the surfactant with shorter hydrophobic chain is preferred,while in the presence of DCA,the surfactant with anionic polar group is preferred.     

Phase-transfer catalysis of a new cationic gemini surfactant with ester groups for nucleophilic substitution reaction

A highly effective phase transfer of a quaternary ammonium gemini surfactant with ester groups（（diethylhexanedioate） diyl-a,v-bis（dimethyl dodecyl ammonium bromide） referred to as 12-10-12）was synthesized with high yield and characterized by infrared spectroscopy, elemental analysis and1 HNMR. Then, 12-10-12 was used as a phase transfer catalyst to study the catalytic effect on the reaction of anhydrous sodium acetate and 4-methylbenzyl chloride. The possible catalytic mechanism and the influence of surfactant concentration, temperature and type are also discussed. The experimental results showed that the catalysis efficiency was more active than the traditional, single-chained surfactant,tetrabutyl ammonium bromide. It also revealed that the reaction was first-order with respect to the concentration of 4-methylbenzyl chloride. The concentration of 4-methylbenzyl chloride grew linearly with the concentration of 12-10-12 and as the reaction temperature increased. The optimum reaction time was 7 h.     

Cation-π Interaction between the Aromatic Organic Counterion and DTAB Micelle in Mixed Solvents

The cation-π interaction between the aromatic organic counterion potassium hydrogen phthalate (KHP) and DTAB micelle in aqueous mixture of EG was investigated, using the techniques of conductivity measurements, UV absorption spectrum and NMR spectrum. The conductivity and UV spectrum studies were with respect to the effect of KHP on DTAB and that of DTAB micelle on KHP, respectively. According to the chemical shift changes of the aromatic ring and the surfactant methylene protons, it can be assumed that KHP penetrated into DTAB micelle with its carboxylic group protruding out of the micellar surface. And the strength of the interaction became weaker with the content of EG in the mixed solvent increasing.     

Effect of Cationic Surfactant on the Gelation of HPAM by Cr（Ⅲ）

The effect of cationic surfactant cetyltrimethylammonium bromide (CTAB) on the gelation of partially hydrolyzed polyacrylamide (HPAM) by Cr(Ⅲ） was investigated by using rheological measurements. The results indicated that the CTAB concentration has a pronounced effect on the viscoelastic properties of the gelling system.     

Structure and physico-chemical properties in mixed aqueous solution of sodium alkvicarboxylate-alkyltrimethylammonium bromide

The physico-chemical properties of organized assemblies (micelle or vesicle ) from sodium alkylcarboxylate - alkyltrimethyl -ammonium bromide mixture have been investigated systematically. In different mixed cationic-anionic surfactant systems, micelles and vesicles can coexist or be transformed into each other on different conditions. The experimental results are explained prelimilarily from the viewpoint of molecular packing geometry. The solubilization of organic compound in the mixed surfactant system was also studied in detail.     

Determination of Cationic Surfactant by Laser Thermal Lens Spectrometry

A novel method for the determination of cationic surfactant by laser thermal lens spectrometry was developcd,It was based on reaction between 1-hydroxy-2-(5-nitro-2-Pyri-dylazo)-8-aminonaphthaenc-3,6-disulfonic acid (5-NO2-PAH) and cationic surfactant to form 1:2 ionic association complex in a weakly basic medium (pH 9.44),The determination conditions and the mechanism were discussed,The method has been appliced to the analysis of wastewater and moat water samples.     

“Noodle-like” Mesoporous Silica Templated by Polyelectrolyte／Surfactant Complex

“Noodle-like” mesoporous silica with a diameter of about 180 nm and a length of ca. 10μm was prepared through sol-gel process by using poly(sodium 4-styrenesulfonate) (PSS)/cetyltrimethylammonium bromide (CTAB) complex as template. Parallel oriented regular mesopores with a diameter of around 2-4 nm are distributed along the wall of the particles, while the “worm-like” disordered mesopores can be found in the fringe part. This approach provides a new series of templates and a novel route to prepare inorganic mesoporous materials with special morphology.     

BINDING OF IONIC SURFACTANTS ON OPPOSITELY CHARGED POLYELECTROLYTES OBSERVED BY FLUORESCENCE METHODS

Our recent studies concerning the binding of ionic surfactants on oppositely charged polyelectrolytes observedwith fluorescence techniques are reviewed. The cationic surfactants cetyltrimethylammonium bromide (CTAB),dodecyltrimethylammonium chloride (DTAC), and nonionic surfactant octaethylene glycol monododecyl ether (C_(12)E_8) wereallowed to bind on anionic poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) and its pyrene and/or naphthalenelabeled copolymers. The relative excimer emission intensity I_E/I_M of a cationic probe l-pyrenemethylamine hydrochloride(PyMeA·HCl) and the non-radiative energy transfer (NRET) I_(Py)/I_(Np) of naphthalene to pyrene for labeled polyelectrolyteswere chosen to monitor the binding process and the conformation change of surfactant-bound polyelectrolytes. The 1:1aggregation of polyelectrolyte-CTAB with respect to the charge was found as long as the CTAB concentration was slightlyhigher than its critical aggregation concentration (CAC). The intermolecular NRET indicated that the CTAB-boundpolyelectrolytes aggregated together through the hydrophobic interaction between the CTAB tails. However, neither 1:1polyelectrolyte-DTAC aggregation nor intermolecular aggregation of DTAC-bound polyelectrolyte was observed owing to itsweaker hydrophobicity of 12 carbon atoms in the tail, which is shorter than that of CTAB. As known from the fluorescenceresults, nonionic surfactant C_(12)E_8 did not bind on the anionic polyelectrolytes, but the presence of PAMPS promoted themicelle formation for C_(12)E_8 at the CAC slightly below its critical micelle concentration (CMC). The solid complex of dansyllabeled AMPS copolymer-surfactant exhibited a decrease in local polarity with increasing charge density of thepolyelectrolyte or with alkane tail length of the surfactant. SAXS suggested a lamella structure for the AMPS copolymer-surfactant solid complexes with a long period of 3.87 nm for CTAB and 3.04 nm for DTAC, respectively.     

Quenching of zinc phthalocyanine excited states by viologen surfactant assemblies——The influence of microenvironment

A series of functional surfactants of N-alkyl-N'-butyl viologens has been synthesized.The quenching of excited singlet and triplet states of zinc phthalocyanine was studied in DMSOand in mixed micelles containing the functional surfactant as one and cationic cetyl trimethylam-monium bromide(CTAB),anionic sodium dodecylsulfate(SDS)and neutral TX-100 surfactantas the other component.Fluorescence quenching and laser photolysis studies indicate that thefunctional surfactants are solubilized at different sites in micelles,the process depends on chainlength and exerts great influence on the quenching of zinc phthalocyanine excited states.     

Formation at low surfactant concentrations and characterization of mesoporous MCM-41

At low concentrations of cetyltrimethylammonium bromide,all silica-based mesoporous materials with hexagonal phase have been synthesized via interactions between self-assembled surfactant molecule aggregates and aniomc silicate polymers.The resulting materials are characterized by XRD,FT-IR,solid state 29Si MAS NMR,thermal analysis and N2 adsorption-desorption measurements.After soluble ions are removed,the interactors between surfactant micelles and silicate polymers are reorganized and then form mesostructures 1 he hexagonal framework is sonsistent with amorphous silica gel.The structures of materials depend on the synthesis conditions Hydrothermal process improves the interactions between molecules and increases the degree of framework silicon atom polymerization The.surface area and the mesopore volume of the material prepared at 100℃ increase by 87% and 71 %,respectively,compared with those obtained at room temperature.     

Synthesis and Characterization of Zirconia Nanocrystallites by Cationic Surfactant and Anionic Surfactant

1 INTRODUCTION Zirconia is a kind of metallic oxide with high mel- ting point. It is highly corrosion-resistant for acid fu- sant and neutral fusant, thus it can be used as refrac- tory material, and it can also be utilized as acid acy- loxy bi-functional catalystic material owing to hav- ing both acid and alkali surface centers[1]. Moreover, zirconia has superior ion-exchange capacity as well as chemical and mechanical stability, therefore, it can also be applied as a catalyst carrier. …     

木素磺酸盐系表面活性剂

木素磺酸盐是化学制浆废液的主要成分,是一种天然高分子表面活性剂。本文介绍了木素磺酸盐系表面活性剂的结构、性能和应用方面的部分研究结果,通过各种改性方法可以改善木素磺酸盐的表面物化性能和应用性能,进一步提高其附加价值及人们对制浆废液治理与回收的积极性,具有环保和经济双重意义。     

特氟隆与含氟表面活性剂

文章就目前困扰世界的特氟隆及含氟表面活性剂进行了简要的介绍。     

Surfactant stabilised colloidal cholesterol

Cholesterol colloids stabilised by Tween 20 (Colloid I), SDS-Et₄ NBr (Colloid II), and CTAB-Nac (Colloid III) were prepared. Moving boundary electrophoresis established Colloid III to be positively charged with a zeta potential of 12.2 mV. Addition of 5 mmol dm^–3 Na₂SO₄ and 0.1 mmol dm^–3 bilirubin dye (Na-salt) decreased the zeta potential to 9.7 mV and 9.5 mV, respectively, by screening the surface charge of the colloidal particles. Higher concentrations of Na₂SO₄ and bilirubin (Na-salt) made making electrophoretic measurements difficult, and such a situation was also faced in the case of Colloid II even without external addition of an electrolyte. Addition of several electrolytes revealed that Colloids II and II were coagulated by the neutralisation of their positive charge, but Colloid I was destabilised by salting-out effect. Measured intrinsic viscosity values and electron microscopic measurements supported overall spherical shape of the colloid particles. Colloid II exibited structural viscosity; higher concentration of NaSO₄ decreased the viscosities of Colloid II and II by electroviscous effect which helped indirect determination of the electrokinetic potential (23.7 mV) of Colloid II.     

可聚合表面活性剂的研究进展

在乳液聚合中，表面活性剂发挥着非常关键的作用，但同时它们也存在不足的方面，一个比较有前景的方法就是使用可聚合表面活性剂。可聚合表面活性剂以牢固的共价键键合到聚合物粒子上，有效避免了表面活性剂的解析及其在膜中的迁移。本文综述了近年来可聚合表面活性剂的进展，主要讨论了阴离子、非离子、阳离子可聚合表面活性剂的特征和性质及其在乳液聚合中的应用。     

Surfactant properties of lignosulfonates

The effect of condition of the sulfite delignification on the surfactant properties of technical lignosulfonates was estimated by the Wilhelmy method.     

Surfactant Enhanced Non-Classical Extraction

Surfactant enhanced non-classical extractions are presented and discussed. They include micellar enhanced ultrafiltration and cloud point extraction. The ideas of the processes are given and the main features are presented. They are compared to the classical solvent extraction. The fundamental of micellar solutions and their solubilisation abilities are also discussed.     

Use of Micellar-Enhanced Ultrafiltration at Low Surfactant Concentrations and with Anionic-Nonionic Surfactant Mixtures

Micellar-enhanced ultrafiltration is a separation technique which can be used to remove metal ions or dissolved organics from water. Metal ions bind to the surface of negatively charged micelles of an anionic surfactant while organic solutes tend to dissolve or solubilized within the micelles. The mixture is then forced through an ultrafiltration membrane with pore sizes small enough to block passage of the micelles and associated metal ions and/or dissolved organics. Monomeric or unassociated surfactant passes through the membrane and does not contribute to the separation. This paper considers advantages of addition of small concentrations of nonionic surfactant to an anionic surfactant; the resulting anionic-nonionic mixed micelles exhibit negative deviation from ideality of mixing which leads to a smaller fraction of the surfactant being present as monomer and a subsequently larger fraction present in the micellar form. The addition of nonionic surfactant improved the separation of divalent zinc substantially at total concentrations above the critical micelle concentration (cmc) of the anionic surfactant. Both zinc and tert-butylphenol (a nonionic organic solute) show unexpected rejection at surfactant concentrations moderately below the cmc, where micelles are absent. This is considered as due to a higher surfactant concentration in the gel layer adjacent to the membrane where micelles are present. Reduction of this rejection at lower transmembrane pressure drops supports this mechanism. Some rejection of zinc was observed in the absence of surfactant but not of tert-butylphenol, indicating an additional effect of membrane charge for ionic solutes. Copyright 1999 Academic Press.