Adsorption of ionic surfactants on polar surfaces with a low content of chemically adsorbed alkyl chains

Colloidal silica and titanium dioxide were surface-modified by chemisorption of octadecyl dimethylmethoxy silane. The surface density of these alkyl silane groups was adjusted to less than 7% of the available surface hydroxyls, leaving the adsorbents hydrophilic and electrically charged in aqueous solution.Ionic surfactants (tetradecylpyridinium chloride and sodium lauryl sulfate) are adsorbed onto the surface-modified silica and titanium dioxide from aqueous solution, even in the case where the surface of the adsorbents exhibits the same sign of electrical charge as the surfactant ionic head groups. According to the adsorption model of Gu the chemiadsorbed alkyl chains are supposed to serve as anchors for small surface aggregates of the ionic surfactants.     

Adsorptive Voltammetry of Polyelectrolyte Complex Between 11‐Ferrocenyltrimethylundecylammonium and Polyanions at Carbon Paste Electrode

For polyelectrolyte complex between cationic surfactant and polyanion, the adsorptive voltammetry at carbon paste electrode using an electroactive cationic surfactant was examined. The adsorption state of the cationic surfactant in the complexes at CPE was estimated from the half‐height width of the oxidation waves. The half‐height width for poly(styrene sulfonate) was independent of the molecular weight, and was same as that for poly(vinyl sulfate). The half‐height width for heparin was broad and different from that of the vinyl polyanions. According to the analysis by Frumkin isotherm, the interaction between cationic surfactants was attractive in heparin complex at CPE, however, in the vinyl polyanion complexes at CPE the interaction was non‐cooperative as that predicted with the Langmuir isotherm. In spite of the same adsorption state, the concentration dependency of the peak current for poly(styrene sulfonate) was quite different from that for poly(vinyl sulfate). The concentration dependence indicated the reactive property of each polyanion on the association with the cationic surfactant in aqueous solution.     

A lyotropic nematic phase of lamellar micelles (N L) obtained by a non-ionic surfactant in aqueous solution

A non ionic surfactant with a rigid rod-like hydrophobic group has been synthesized. Owing to the molecular geometry of the surfactant only lamellar micelles are formed in aqueous solution.This system exhibits a lyotropic nematic phase (N _L), which for the first time has been found for a binary non ionic surfactant/water system.Herrn Professor Dr. H.-G. Kilian mit herzlichen Glückwünschen zum 60. Geburtstag gewidmet.     

Synthesis of conducting polyaniline using novel anionic Gemini surfactant as micellar stabilizer

The Gemini surfactant 9B-4-9B containing sodium sulfonate as hydrophilic head group was synthesized based on nonylphenol and characterized by FTIR, ¹H NMR spectroscopy and the surface tension measurement. The CMC and C₂₀ of the 9B-4-9B were smaller than that of sodium dodecylbenzene sulfonate and sodium dodecylsulfate, respectively, indicating excellent efficiency of micelle formation and reduced surface tension. Conducting polyaniline salts were synthesized by chemical oxidative micellar polymerization of aniline in water firstly using Gemini surfactant 9B-4-9B as the micelle stabilizer and ammonium peroxydisulfate as the oxidant at 0 °C. The stable polyaniline dispersions have been obtained when the molar ratio of the 9B-4-9B to aniline was equal to or above 0.5 used in the polymerization system. The obtained granular polyaniline particles with the size of 1-2 μm were characterized by FTIR, UV-Vis, SEM, WAXD and conductivity measurement.     

Surfactant in the gaseous phase II. Influence on stability of foams and thin liquid films

The influence of the vapors ofn-amyl orn-decyl alcohol on the stability of single thin liquid films, single bubbles, and foam columns was determined. It was found that the presence of surfactant vapors lowered the stability of foams and single foam films. The mechanism of the destabilizing action of the surfactant vapors on wet, dynamic foams under dynamic conditions is discussed. It is shown that the destabilizing action of the surfactant vapors is a further indication that surface elasticity forces are the main factor determining stability of wet, dynamic foams.     

Conformation of poly(L-glutamic acid) in aqueous solutions of linear amphiphiles with a cationic group at both ends

The conformations of poly(l-glutamic acid) [P(Glu)] in solutions of the bipolar amphiphile 1,20-icosanediylbis(alkylammonium chloride) [C20(RA)₂], where RA includes trimethylammonium (TMA), dimethylammonium (DMA), or methylammonium (MA), were investigated with measurements of the circular dichroism spectra at 10–35 °C. All C20(RA)₂ induced an α-helix of P(Glu) in the aqueous solutions. The residue molar ellipticity at 222 nm showed a similar dependence on the amphiphile concentration (C _s) below 0.5 of the ratio of 2C _s to the residue concentration (C _p) of P(Glu), but it separated into three directions at 2C _s/C _p>0.5. C20(MA)₂ induced an α-helix of P(Glu) at 2C _s/C _p<0.5 followed by a helix aggregate at 2C _s/C _p>0.5. C20(DMA)₂ and C20(TMA)₂ also induced an α-helix, but a helix aggregate. C20(TMA)₂ indicated a strong temperature dependence and did not induce a complete α-helix at 35 °C. Received: 20 June 2001 Accepted: 6 September 2001     

Surfactant-Assisted Assembly of Dipeptide Forming a Broom-like Structure

Understanding the influence of surfactants on the assembly of peptides has a considerable practical motivation. In this paper, we systematically study the anionic surfactant-assisted assembly of diphenylalanine (FF). FF forms broom-like structures in a concentration of sodium cholate (NaC) around the CMC, and assembles into linear and unidirectional rods in the presence of low and high surfactant concentrations. FF’s improved hydrogen bonding and controlled assembly rates are appropriate for other anionic surfactants. At this stage, the use of FF as the simplest protein consequence can be helpful in the investigation of further protein–surfactant interactions.     

Effect of Surfactant Type and Concentration on Surfactant Migration,Surface Tension,and Adhesion of Latex Films

The effect of surfactant type and concentration on the migration behavior of surfactant in a latex film was investigated. Two types of surfactant, including an anionic (sodium lauryl sulfate, SLS) and a non-ionic (nonylphenol ethoxylate, average number of ethylene oxide units = 40, NP-40) surfactant, were used in an emulsion polymerization of methyl methacrylate butyl acrylate copolymer (MMA–BA). The total amount of surfactant was varied in three levels, i.e., 1.5, 3, and 4.5 wt%, and the surfactants were used both pure and in a mixture state. The surfactant migration to the film–air (F–A) and film–substrate (F–S) interfaces of the latex films was determined by using an attenuated total reflection-Fourier transform infrared (ATR-FTIR) method. In addition, the adhesion of the latex films to glass substrates was measured by a pull-off test. The results showed that the migration of anionic surfactant to the interfaces was greater than the non-ionic one. It was also found that the use of non-ionic surfactant along with anionic surfactant could decrease the migration of the anionic surfactant to the interfaces.     

TX-100和CTAB交换动力学的核磁共振研究

运用核磁共振(NMR)方法分别测定了表面活性剂辛基苯聚氧乙烯醚(TX-100)和十六烷基三甲溴化铵(CTAB)在不同温度下的临界胶束浓度.阐述了应用1D NMR线型分析方法对表面活性剂快交换体系平均停留时间的定量测量.实验测量了TX-100和CTAB胶束溶液中表面活性剂分子在不同温度下的平均停留时间.结果显示,平均停留时间随温度的增加逐渐减小,说明TX-100和CTAB分子进出胶束的速率随温度的增加逐渐加快.利用阿伦尼乌斯公式拟合,获得了TX-100和CTAB的表观交换活化能,TX-100的表观交换活化能为17.6 k J/mol,CTAB的表观交换活化能为75.3 k J/mol.对TX-100和CTAB平均停留时间和表观交换活化能进行分析,得出平均停留时间和表观交换活化能与分子结构的关系:表观交换活化能反映的是疏水相互作用和静电斥力的大小;而平均停留时间不仅受活化能的影响,还与分子结构有关.     

Surfactant‐assisted specific‐acid catalysis of Diels–Alder reactions in aqueous media

Surfactant‐assisted specific‐acid catalysis (SASAC) for Diels–Alder reactions of dienophiles 1 and 4 with cyclopentadiene 2 in aqueous media at 32 °C was studied. This study showed that acidified anionic surfactants (pH 2) such as sodium dodecyl sulfate (SDS) and linear alkylbenzene sulfonic acid (LAS) accelerate Diels—Alder reactions. Conversely, under similar reaction conditions (pH 2) these reactions are inhibited by (acidified) cationic surfactants such as dodecyltrimethylammonium bromide (DTAB), dodecyldimethylammonium bromide (DDAB), and dodecylmethylammonium bromide (DMAB). A modest rate acceleration resulting from the surfactant hydrogen‐bonding capacity is also recorded for the Diels–Alder reaction of naphthoquinones ( 6 ) with cyclopentadiene ( 2 ) in aqueous media at 32 °C. Copyright © 2007 John Wiley & Sons, Ltd.