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Showing papers in "Langmuir in 1990"


Journal ArticleDOI
01 Jan 1990-Langmuir
TL;DR: In this paper, a phenomenes de mouillage et d'adsorption d'une surface solide are described, e.g., adaption of alcanethiols and sulfures de dialkyl sur de l'or
Abstract: Etude des phenomenes de mouillage et d'adsorption d'une surface solide. Application a l'adsorption d'alcanethiols et de sulfures de dialkyl sur de l'or

868 citations


Journal ArticleDOI
01 Mar 1990-Langmuir
TL;DR: Etude de la permeabilite, de la structure and des proprietes electrochimiques des couches monomoleculaires de polyfluoro alcanethiol deposees sur une electrode d'or as discussed by the authors.
Abstract: Etude de la permeabilite, de la structure et des proprietes electrochimiques des couches monomoleculaires de polyfluoro alcanethiol deposees sur une electrode d'or

624 citations


Journal ArticleDOI
01 Mar 1990-Langmuir
TL;DR: In this paper, the authors used CIR-FTIR, adsorption isotherm, and electrophoretic mobility data to calculate the intrinsic pK value (4.6) for the bridging bidentate iron phosphate surface complex.
Abstract: CIR-FTIR in situ spectroscopic studies have provided evidence for the formation of three different type of complexes, protonated and nonprotonated bridging bidentate as well as a nonprotonated monodentate, between orthophosphate ions and surface Fe(III) of {alpha}-FeOOH particles in aqueous suspensions. The speciation of these complexes is a function of pH and phosphate surface coverage ({Lambda}). Furthermore, the combination of CIR-FTIR, adsorption isotherm, and electrophoretic mobility data allows them to calculate the intrinsic pK value (4.6) for the bridging bidentate iron phosphate surface complex.

484 citations


Journal ArticleDOI
01 Jan 1990-Langmuir
TL;DR: In this article, the structures of nonaqueous suspensions subjected to electrical fields and continuous shear are described, and models for the yield stress and continuous-shear response of these electrorheological (ER) suspensions are developed.
Abstract: The structures of nonaqueous suspensions subjected to electrical fields and continuous shear are described. Based on observations that particle strands and columns formed upon application of an electric field behave as elastic solids for small shear strains but yield above a critical strain, models for the yield stress and continuous-shear response of these electrorheological (ER) suspensions are developed. Comparison of model calculations with experimental results indicates that the yield stress is dominated by the work required to overcome electrically induced interparticle forces.

409 citations


Journal ArticleDOI
01 Jun 1990-Langmuir
TL;DR: The influence of the dimension des particules sur le depot de polystyrene sur un lit de particules spheriques de verre is studied in this paper, where the dimension of polystyrenes is defined as:
Abstract: L'influence de la dimension des particules sur le depot de particules de polystyrene sur un lit de particules spheriques de verre est etudiee theoriquement et experimentalement

382 citations


Journal ArticleDOI
01 Jan 1990-Langmuir
TL;DR: In this paper, the authors discuss the phenomenon of electrorheology in relation to possible mechanisms involving polarization of dispersions in flow and make comparisons between electorheological activity and dielectric properties.
Abstract: The phenomenon of electrorheology is discussed in relation to possible mechanisms involving polarization of dispersions in flow. Data relating such polarization during flow are presented, and comparisons between electrorheological activity and dielectric properties are made. The importance of the rate of polarization as well as its magnitude is stressed. How such considerations led to electrorheological fluids based on dispersed semiconducting polymers as an alternative to traditional water containing polyelectrolytes is discussed, and some of the dielectric and electrorheological properties of these new electrorheological fluids are described.

380 citations


Journal ArticleDOI
01 Feb 1990-Langmuir
TL;DR: In this paper, the formation of micelles de poly(oxyethylene) and polystyrene dans l'eau est etudiee par fluorescence.
Abstract: La formation des micelles de poly(oxyethylene) et de polystyrene dans l'eau est etudiee par fluorescence

318 citations


Journal ArticleDOI
01 Nov 1990-Langmuir
TL;DR: In this paper, a series of trichlorosilyl-terminated surfactants have been used to create a set of variously functionalized self-assembled monolayer surfaces.
Abstract: A series of new trichlorosilyl-terminated surfactants have been used to create a set of variously functionalized self-assembled monolayer surfaces. Transformations of these surfaces, with a focus on the use of nucleophilic substitution reactions for the creation and interconversion of surfaces with nitrogen- and sulfur-containing functionality, are reported. Approaches to the characterization of these surfaces and to the assessment of the efficacy of such in situ chemical transformations are explored. The use of such reactions to create new surface functionality and bridged monolayer structures is described

315 citations


Journal ArticleDOI
01 Apr 1990-Langmuir
TL;DR: In this paper, the authors consider the results of both old and new experiments and conclude that these so-called hydration forces are not due to water structure, but rather to the strongly repulsive short-range force between amphiphilic surfaces.
Abstract: The strongly repulsive short-range force between amphiphilic surfaces has, since Langmuir, been associated with how these surfaces modify the local water structure. We consider the results of both old and new experiments and conclude that these so-called «hydration» forces are not due to water structure

224 citations


Journal ArticleDOI
01 Feb 1990-Langmuir
TL;DR: In this paper, the authors extended their earlier work to include oil phases comprised of 100% styrene or 100% divinylbenzene and evaluated the effects of these phases on the microstructure and compressive properties of open cell foams.
Abstract: High internal phase emulsions (HIPEs) provide an attractive route to open cell foams. In this paper, we extend our earlier work to include oil phases comprised of 100% styrene or 100% divinylbenzene. In addition, we have evaluated the effects oil-soluble versus water-soluble polymerization initiators, aqueous-phase salt concentrations, and the degree of cross-linking on the microstructure and compressive properties. Foam cell sizes were found to be inversely related surfactant level, relatively insensitive to increases in the monomer levels, but greatly affected by salt concentration. The best textured foams generally had the best formed cells and the most open microstructure.

203 citations



Journal ArticleDOI
01 Apr 1990-Langmuir
TL;DR: Les particules colloidales monodispersees de silice avec diameters of 50 a 700 nm sont preparees par hydrolyse de tetraethyl orthosilicate dans l'eau, l'ammoniac et l'ethanol.
Abstract: Les particules colloidales monodispersees de silice avec des diametres de 50 a 700 nm sont preparees par hydrolyse de tetraethyl orthosilicate dans l'eau, l'ammoniac et l'ethanol. L'aire superficielle et la porosite de ces particules sont determinees par la methode BET et par thermogravimetrie

Journal ArticleDOI
01 Feb 1990-Langmuir
TL;DR: La microscopie a reflexion totale interne is a nouvelle technique utilisee for mesurer directement le potentiel moyen de l'interaction entre a sphere microscopique and a plaque en verre as mentioned in this paper.
Abstract: La microscopie a reflexion totale interne est une nouvelle technique utilisee pour mesurer directement le potentiel moyen de l'interaction entre une sphere microscopique et une plaque en verre

Journal ArticleDOI
01 Aug 1990-Langmuir
TL;DR: In this article, the primary reaction intermediates in titanium dioxide (TiO{sub 2}) photosensitized reactions of potassium iodide, 2,4,5-trichlorophenol, methyl viologen dichloride, potassium tetrachloroplatinum(II), tris(1,10-phenanthroline)-iron(II) perchlorate, N,N,N{prime}, N{prime}-tetramethyl-p-phenylenediamine, and thianthrene.
Abstract: Diffuse reflectance and transmission flash photolysis have been used to study the primary reaction intermediates in titanium dioxide (TiO{sub 2}) photosensitized reactions of potassium iodide, 2,4,5-trichlorophenol, methyl viologen dichloride, potassium tetrachloroplatinum(II), tris(1,10-phenanthroline)-iron(II) perchlorate, N,N,N{prime},N{prime}-tetramethyl-p-phenylenediamine, and thianthrene. In the cases where the product of OH radical mediated oxidation is different from that of direct electron transfer oxidation, only products of direct electron transfer oxidation are observed. The products of direct electron transfer and OH radical mediated oxidation of iodide and tetrachloroplatinum are identical. The transient decay kinetics in TiO{sub 2} powder systems appear to be first order with a Gaussian distribution of reaction rate constants reflecting the distribution of particle radii.

Journal ArticleDOI
01 Mar 1990-Langmuir
TL;DR: Les caracteristiques electrocinetiques du mica en contact avec des ions monovalents, trivalents, divalents dans une solution aqueuse sont mesurees as discussed by the authors.
Abstract: Les caracteristiques electrocinetiques du mica en contact avec des ions monovalents, trivalents, divalents dans une solution aqueuse sont mesurees

Journal ArticleDOI
01 Aug 1990-Langmuir
TL;DR: Les spectres infrarouges d'une silice pyrogenee et de silices preparees en phase liquide (aqueuse ou alcoolique) sont compares as discussed by the authors.
Abstract: Les spectres infrarouges d'une silice pyrogenee et de silices preparees en phase liquide (aqueuse ou alcoolique) sont compares

Journal ArticleDOI
01 May 1990-Langmuir
TL;DR: La spectrometrie IR a transformation de Fourier is utilisee in situ for etudier la structure des complexes superficiels formes apres adsorption de benzoate et de phenolate sur des particules de α-FeOOH en suspension dans l'eau as discussed by the authors.
Abstract: La spectrometrie IR a transformation de Fourier est utilisee in situ pour etudier la structure des complexes superficiels formes apres adsorption de benzoate et de phenolate sur des particules de α-FeOOH en suspension dans l'eau

Journal ArticleDOI
01 Oct 1990-Langmuir
TL;DR: In this paper, the authors describe a way to form multiple asymmetric layers of organic molecules that may be applicable to the fabrication of electrooptical switching elements and other second-order nonlinear optical devices.
Abstract: We describe a way to form multiple asymmetric layers of organic molecules that may be applicable to the fabrication of electrooptical switching elements and other second-order nonlinear optical devices. The molecular layers are formed sequentially and are held together by strong zirconium phosphate and zirconium phosphonate bonds. Such multilayer films have been constructed on both gold and oxidized silicon surfaces

Journal ArticleDOI
01 Jan 1990-Langmuir
TL;DR: Le role des modificateurs de surface (derive du pyridyl-4) dans les reactions de transfert d'electron du cytochrome c sur une electrode d'or est etudie as mentioned in this paper.
Abstract: Le role des modificateurs de surface (derive du pyridyl-4) dans les reactions de transfert d'electron du cytochrome c sur une electrode d'or est etudie

Journal ArticleDOI
01 Feb 1990-Langmuir
TL;DR: In this paper, the influence of adsorbed CO formed by dissociative chemisorption on the electrooxidation pathways and kinetics of 22 alcohols and aldehydes on polycrystalline platinum and palladium electrodes in relation to the adaption of CO was examined systematically by means of real-time sequences of FTIR spectra obtained during slow (2 mV s{sup {minus}1}) voltammetric sweeps in 0.1 M HClO{sub 4}.
Abstract: The influence of adsorbed CO formed by dissociative chemisorption on the electrooxidation pathways and kinetics of 22 alcohols and aldehydes on polycrystalline platinum and palladium electrodes in relation to the adsorbed CO formed by dissociative chemisorption has been examined systematically by means of real-time sequences of FTIR spectra obtained during slow (2 mV s{sup {minus}1}) voltammetric sweeps in 0.1 M HClO{sub 4}. The overall objective is to explore the reactant structure-dependent role that adsorbed CO (and other CO{sub 2}-producing species) plays in the organic electrooxidation. The reactants examined include short-chain primary and secondary alcohols, aldehydes, and small bifunctional molecules (e.g., ethylene glycol) containing alcohol, aldehyde, and/or carboxylic acid units.

Journal ArticleDOI
01 Nov 1990-Langmuir
TL;DR: Marangoni drying as mentioned in this paper is a new drying process in which the substrate to be dried is withdrawn from a rinse bath (water) while at the same time nitrogen gas with a trace of an organic vapor is led along its surface.
Abstract: In a new drying process (referred to as Marangoni drying), the substrate to be dried is withdrawn from a rinse bath (water) while at the same time nitrogen gas with a trace of an organic vapor is led along its surface The organic vapor dissolves into water and introduces a surface tension gradient in the wetting film on the substrate, causing the water film to quickly drain backwards into the rinse batch (a Marangoni effect) As a result, a completely dry substrate emerges from the bath Contrary to spin drying, almost no contamination is added to the substrate surface during drying

Journal ArticleDOI
01 May 1990-Langmuir
TL;DR: In this article, specular reflection of neutrons has been used to study the structure of a layer of hexadecyltrimethylammonium bromide adsorbed at the interface between a plate of amorphous silica and solutions of C{sub 16}TAB.
Abstract: The technique of specular reflection of neutrons has been used to study the structure of a layer of hexadecyltrimethylammonium bromide (C{sub 16}TAB) adsorbed at the interface between a plate of amorphous silica and solutions of C{sub 16}TAB. At concentrations of 1/3 and 2/3 the cmc (9 {times} 10{sup {minus}4} M), the structure which best fitted the reflectivity data can be described either as a defective bilayer or as flattened micelles. The thicknesses of the alkyl chain and head-group regions of the bilayer were found to be 28 {plus minus} 4 and 6 {plus minus} 2 {angstrom}, respectively. At 6 {times} 10{sup {minus}4} M, 80% of the interface was covered with bilayer, and this dropped to 35% at 3 {times} 10{sup {minus}4} M. At both coverages, the head-group area was found to be 30 {plus minus} 3 {angstrom}{sup 2}.

Journal ArticleDOI
01 Feb 1990-Langmuir
TL;DR: In this article, an organized monolayer of octadecanethiol on a gold electrode strongly inhibits faradaic reactions except at pinholes in the monolayers, which are selectively and permanently passivated by electrochemical polymerization of phenol in dilute sulfuric acid.
Abstract: An organized monolayer of octadecanethiol on a gold electrode strongly inhibits faradaic reactions except at pinholes in the monolayer. For simple outer-sphere redox couples, the monolayer-coated electrode behaves like a microelectrode array, with pinholes acting as the microelectrodes. The average size and separation of the pinholes can be estimated by fitting the experimental cyclic voltammograms with simulated voltammograms for a microarray electrode. The pinholes are selectively and permanently passivated by electrochemical polymerization of phenol in dilute sulfuric acid.


Journal ArticleDOI
01 Jun 1990-Langmuir
TL;DR: In this article, the authors proposed an explanation for the stepwise thinning of thin liquid films formed from micellar solutions or latex suspensions by layer-by-layer destruction of a colloid crystal structure inside the film.
Abstract: The stratification of thin liquid films formed from micellar solutions or latex suspensions can be explained by layer-by-layer destruction of a colloid crystal structure inside the film. The stepwise decrease of the film thickness is due to appearance and growth of dark spots (of less thickness) in the film. This phenomenon is analyzed in the present paper, and an explanation is proposed. The driving force for the stepwise thinning of the film is attributed to the gradient of the chemical potential of micelles at the film periphery. Therefore, the appearance and expansion of spots in the film are controlled by the micellar self-diffusion, rather than by normal instabilities. The spots are considered as condensed states of vacancies in the micellar structure inside the film, and the appearance of dark spots is interpreted as a phase transition. This explanation of the mechanism of stratification phenomenon is supported by the data for formation and expansion of spots.

Journal ArticleDOI
01 Nov 1990-Langmuir
TL;DR: In this article, images of dilute lamellar (Lα) and anomalolus isotropic (L 3 ) phases obtained by freeze fracture electron microscopy are presented.
Abstract: We show images of dilute lamellar (Lα) and anomalolus isotropic (L 3 ) phases obtained by freeze fracture electron microscopy. The images of the Lα phase show stacks of bilayers. In some parts, undulations of the bilayers may be seen. The images from the L 3 phase show an apparently bicontinuous network of two aqueous subvolumes separated by a random bilayer network. Saddle point structures with a mean curvature close to zero and a negative Gaussian curvature are observed. The bilayers are separated by several hundred angstroms, and the repeat distances seen on the images agree with those measured previously by SANS

Journal ArticleDOI
02 Jan 1990-Langmuir
TL;DR: In this paper, the authors showed that electrically conductive polymers with fibrillar supermolecular structures can be prepared by synthesizing the polymer within the pores of a microporous membrane.
Abstract: The authors have shown that electrically conductive polymers with fibrillar supermolecular structures can be prepared by synthesizing the polymer within the pores of a microporous membrane. In this paper, they compared charge transport rates in fibrillar polypyrrole with the corresponding rates in conventional polypyrrole films; charge transport rates in the fibrillar versions were found to be significantly higher.

Journal ArticleDOI
01 Mar 1990-Langmuir
TL;DR: In this article, a nonconjugated hydrocarbon film was studied for electron transfer in which the sulfide attached to the gold and the hydrocarbon chains oriented such that the resulting monolayer films had the electroactive group fixed a distance of 5, 7, or 10 CH{sub 2} groups from the surface.
Abstract: Electron transfer through a nonconjugated hydrocarbon film was studied. 1-Methyl-1{prime}-(10-(octadecylthio)decyl)-4,4{prime}-bipyridinium dibromide, 1-(7-(octadecylthio)heptyl)-1{prime}-propyl-4,4{prime}-bipyridinium dibromide, and 1-hexyl-1{prime}-(5-(octadecylthio)pentyl)-4,4{prime}-bipyridinium dibromide were synthesized and were separately self-assembled with octadecyl mercaptan onto Au electrodes. The sulfide attached to the gold, and the hydrocarbon chains oriented such that the resulting monolayer films had the electroactive group fixed a distance of 5, 7, or 10 CH{sub 2} groups from the surface, which was about 7-12 {angstrom}, depending on the angle of the chains to the surface. The films were characterized by cyclic voltammetry, FTIR, and ellipsometry. Electron transfer depended on the distance of the electroactive group from the surface and was facile in all cases.

Journal ArticleDOI
01 Dec 1990-Langmuir
TL;DR: In this article, the random copolymer poly(2-vinylpyridine-co-p-aminostyrene) was used as a steric stabilizer.
Abstract: Colloidal polyaniline has been prepared in acidic aqueous media by chemical grafting of polyaniline onto a tailor-made polymeric surfactant. The surfactant, which acts as a steric stabilizer, used in this study is the random copolymer poly(2-vinylpyridine-co-p-aminostyrene). This surfactant contains pendant aniline units which participate in the aniline polymerization, resulting in the formation of sterically stabilized polyaniline particles which have a nonspherical «rice grain» morphology

Journal ArticleDOI
01 Mar 1990-Langmuir
TL;DR: In this article, general equations for describing diffusion on the heterogeneous surface in the framework of the lattice-gas model were derived and the effect of surface heterogeneity and lateral interactions between adsorbed particles on the coverage dependence of the chemical diffusion coefficient was discussed.
Abstract: General equations are derived for describing diffusion on the heterogeneous surface in the framework of the lattice-gas model. The effect of the surface heterogeneity and lateral interactions between adsorbed particles on the coverage dependence of the chemical diffusion coefficient is discussed.