Formation of uniform silver particles from bis (1,2-ethanediamine)silver(I) complex

Uniform spherical silver particles were produced by decomposing the bis(1,2-ethanediamine)silver(I) complex, by aging a solution of 1.0×10^–3 mole dm^–3 in silver (I) nitrate, 1.0 mole dm^–3 in 1,2-ethanediamine, and 2.5×10^–1 mole dm^–3 in nitric acid (basic solution) at 100°C for 42 min. The average modal diameter was estimated to be 0.52 m with a relative standard deviation of 0.10. A moderately oxygenrich layer, 40 Å thick, on the surface of the particles was detected by means of photoelectron surface microanalysis (XPS). The silver particles grew through a polynuclear-layer mechanism, as judged from the concentration change in soluble silver(I) species in the supernatant solution. The particles' point of zero charge (PZC) was estimated at pH 6.5 by potentiometric titration.     

Estimation of the critical micelle concentrations and the aggregation numbers of sodium alkyl sulfates by capillary-type isotachophoresis

The analytical procedure for the separation and quantification of bulk and micellar phases for sodium alkyl sulfates has been investigated by a capillary-type isotachophoresis using a potential gradient detector. Monomer solutions were distinguished from micellar solutions at pH 5.5–6.0; hydrochloric acid — L-Histidine mixture was used as the leading electrolyte and 2-(N-Morpholino) ethanesulfonic acid as the terminating electrolyte.The potential unit value (PU value) due to the monomer solutions was larger than that due to the micellar solutions. The zone length due to monomer solutions increased with increasing concentration of surfactant until a given concentration (CMC); beyond this point the values became constant. On the other hand, the zone length due to micellar solutions increased from this point. We report an applicability of capillary-type isotachophoresis to determination of the CMC's and aggregation number for various sodium alkyl sulfates.     

Simulation of a monolayer adsorbed on a heterogeneous surface: effect of the size and shape of the adsorbate on the structure of the interface and the distribution of the adsorption energies

At the low temperature limit, the effect on the size and shape factors of the adsorbate molecule is shown in a simulation of a monomolecular phase adsorbed on a heterogeneous surface. This factor is reflected both in the theoretical distribution of the adsorption energies and the packing of the adsorbed phase.     

Role of ionic species and valency on the steady shear behavior of partially hydrolyzed polyacrylamide solutions

Polyacrylamides are anionic polymers with a large number of charges along the polymer chains. The rheological properties of aqueous polyacrylamide solutions can be significantly modified by varying the solvent environment with the addition of salt. The presence of cations substantially reduces the inter- and intra-molecular interactions of the macroions. It was found that the valency of the cation has a strong effect on the rheological behavior of polyacrylamide solutions, but the size and type of salt have a negligible effect.The reduction in the solution viscosity with di-valent salts (e.g., CaCl₂, MgCl₂, BaCl₂, and MgSO₄) can be as high as an order of magnitude compared with mono-valent salt (KI, KC1, NaCl, and NaBr), depending on the salt concentration and shear rate. An identical viscosity function can be obtained for different types of polyacrylamide solutions by varying the salt content in solution. This interesting feature provides a useful means in the development and preparation of certain ideal fluids for simulation studies of complex flow problems.     

An isotachophoresis for the microdetermination of potassium persulphate as initiator in emulsion polymerization

An isotachophoresis (IP) was applied to determine the decomposition rate of potassium persulphate (KPS) as initiator in emulsion polymerization, in comparison with conventional iodometry and ferrometry. For the exact determination, the latter methods needed several milliliters of the emulsion pipetted from the polymerization system, whereas IP did only a few microliters. Moreover, the amount of sulphuric acid produced as the decomposition by-product was simultaneously determined by IP, which is impossible for iodometry and ferrometry.Part CIV of the series Studies on Suspension and Emulsion.     

Conformational changes of polyglutamic acid adsorbed on cationic polystyrene as characterized by microelectrophoresis technique

Polypeptides (polyglutamic acid in sodium form) of three different polymerization degrees have been adsorbed on cationic polystyrene latex. The electrokinetic behavior of the complex PG/PS has been studied by microelectrophoretic mobility. The effect of ionic strength and pH on electrokinetic properties of the complex PG/PS have also been studied. It has been found that the appearance of maximum inu _e -logc curves is related to coverage degree of polystyrene surface and the polymerization degree of polypeptides chains. Likewise, the form of such curves depends markedly on pH. An attempt has been made to explain the data in terms of conformational changes of the adsorbed polypeptides chains.Presented at the NATO Advanced Study Institut on Polymer Colloid, Strasbourg (France), July 1988.     

Rheological investigation of aqueous solutions of poly(vinyl alcohol) during aging II. Influence of experimental conditions on dissolution and aging

The influence of the temperature and time of heating during dissolution on the aging of concentrated aqueous solutions of poly(vinyl alcohol) and aging at different temperatures are described. Changes occuring during aging are interpreted on the basis of non-Newtonian viscosity and normal stress measurements.     

Preparation of composite fine particles by heterocoagulation

To prepare regular composite particles comprised of organic and inorganic compounds, based on heterocoagulation theory, the properties of the mixture of small amphoteric latices (2a=250 nm) and large spherical silica (2a=240–1590 nm) were investigated as a function of pH, particle number ratio, particle size ratio and electrolyte concentration in the medium. It is apparent that under suitable conditions, we may prepare a stable mixed suspension comprising uniform composite particles, which are made up of many latices regularly adsorbed on silica surfaces, and each composite particle is undergoing Brownian motion as an isolated unit. This new composite particle is very stable for electrolyte, base and acid medium, and its surface charges (sign and magnitude) can be controlled by changing the pH of the medium.     

The complex rheological behavior of an aqueous cationic surfactant solution investigated in a Couette-type viscometer

In this paper the behavior of an aqueous surfactant solution in a rotational Couette viscometer is investigated. It is shown that this behavior depends strongly upon time, upon the way in which the flow curve is obtained (with increasing or decreasing shear rate), upon the temperature, and upon the concentration of the solution. Furthermore, the results also reveal a pronounced dependence upon the size of the actual measuring system used. It is shown that the slip-velocity concept is not applicable to explain this dependence.     

Preparation of micron-size monodisperse polymer particles having highly crosslinked structures and vinyl groups by seeded polymerization of divinylbenzene using the dynamic swelling method

Micron-size monodisperse polystyrene/polydivinylbenzene (PS/PDVB) composite particles having highly crosslinked structures and vinyl groups were prepared as follows. First, 1.9 m-size monodisperse PS seed particles produced by dispersion polymerization were dispersed in ethanol/water (70/30, w/w) solution which dissolved divinylbenzene (DVB) monomer, benzoyl peroxide as an initiator and poly(vinyl alcohol) as a stabilizer. The PS seed particles were swollen with a large amount of DVB monomers to 4.3 m in diameter while keeping good monodispersity by the dynamic swelling method, where water was slowly added, continuously, with a micro feeder into the dispersion. And then, the seeded polymerization of the absorbed DVB was carried out.Part CXXXV of the series Studies on Suspension and Emulsion     

Melittin and ionic surfactant interactions in monomolecular films

The interaction between the anionic and cationic surfactants with Melittin spread monolayers at the air-water interface was investigated. The addition of anionic Cl^–, under the films of Melittin gives rise to a change in both surface pressure and surface potential. These interactions are different when surfactants are present, due to specific interactions between Melittin and the ionic-surfactants.     

The acceleration of decomposition of potassium persulfate in the presence of sodium dodecyl sulfate and polymer particles as a model of emulsion polymerization system

The decomposition rates of potassium persulfate (KPS) in aqueous solutions containing sodium dodecyl sulfate (SDS) in the presence of polystyrene or poly(methyl methacrylate) particles as models of emulsion polymerization systems were measured by isotachophoresis. Free SDS molecules dispersed in the monomolecular state had an ability to accelerate the KPS decomposition, but SDS molecules adsorbed onto the polymer particles did not accelerate it.Part CXX of the series of Studies on Suspension and Emulsion     

Spectrophotometric behavior of polyvinylpyrrolidone in aqueous and nonaqueous media (I)

Electronic spectral behavior of polyvinylpyrrolidone solutions in various media has been determined by UV-VIS spectrophotometry. A theoretical approach has been developed to explain the experimentally observed concentration dependent spectral behavior of polyvinyl pyrrolidone in aqueous and nonaqueous solvents. Increase in the concentration of the polymer or the addition of guanidine salts caused bathochromic shift. A similar concentration effect has been observed in nonaqueous media in the absence of guanidine salts.     

The electrophoretic deposition of polyvinyl chloride organosol from organic medium

The results of the studies on the influence of PVC organodispersions properties on the gram-equivalent (Q) of organosol electrophoretically deposited on the electrode have been presented in this work. The influence of the electrical conductivity and organosol concentration on electrophoresis have been determined. The mechanism of organosol particle-potential formation with respect to swelling processes and dispersive agent adsorption have been pointed out.     

Effect of inorganic electrolyte concentration on anionic-cationic adsorption films Part 1. Decylpyridinium chloride + sodium octylsulphonate + sodium chloride

The effect of NaCl on simultaneous adsorption of decylpyridinium chloride (R₁₀PyCl) and sodium octylsulphonate (R₈SO₃Na) on the free surface of their aqueous solutions has been examined. The surface excess of each component was determined on the basis of a suitable form of the Gibbs adsorption equation. The ionic strength effect on the adsorption of particular components of mixtures, as well as on the composition of anionic-cationic films adsorbed from equimolar solutions, is small. This is due to little difference in surface activity of surfactants investigated.     

Fluorescence and viscometry study of complexation of poly(acrylic acid) with poly(acrylamide) and hydrolysed poly(acrylamide)

Interpolymer complexation of poly(acrylic acid) with poly(acrylamide) and hydrolysed poly(acrylamide) was studied by fluorescence spectroscopy and viscometry in dilute aqueous solutions. Changes in chain conformation and flexibility due to the interpolymer association are reflected in the intramolecular excimer fluorescence of pyrene groups covalently attached to the polymer chain. Both poly(acrylamide) and hydrolysed poly(acrylamide) form stable complexes with poly(acrylic acid) at low pH. The molecular weight of poly(acrylic acid) and solution properties such as pH and ionic strength were found to influence the stability and the structure of the complexes. In addition, the polymer solutions mixing time showed an effect on the mean stoichiometry of the complex. The intrinsic viscosity of the solutions of mixed polymers at low pH suggested a compact polymer structure for the complex.     

Polymer coatings onto anodized aluminum plate by anodic electrodeposition from alkali-swollen carboxylated acrylic emulsion

Polymer coating of an anodized aluminum plate was carried out by anodic electrodeposition from alkali-swollen ethyl acrylate-methyl methacrylate-methacrylic acid (45/45/10, mole ratio) terpolymer emulsion with dimethyl aminoethanol. The alkali-swollen state was controlled by heating time at 60°C prior to the elctrodeposition. The similar complicated behaviors were observed in the relationships between the alkali-swollen state and the primary current density, the current density after 2 min, the quantity of electricity, and the amount of polymer deposited. The appearance of coatings changed correspondingly with such behaviors. These results indicate that the properties of the coatings are complicatedly affected by the degree of alkali-swollen state.Part CXII of the series Studies on Suspension and Emulsion.     

Production of anomalously shaped carboxylated polymer particles by seeded emulsion polymerization

Anomalous polymer particles with a partial protuberance like octopus ocellatus were produced under alkaline conditions by seeded emulsion copolymerization for styrene and butyl acrylate, with styrene-butyl acrylate-methacrylic acid terpolymer emulsion as seed. The mechanism of production of the polymer particles was studied. By transmission electron microscopic observation of the particles at each conversion, it was observed that the anomalous polymer particles were produced by partial growth of each of the individual seed particles throughout polymerization. Ionization of the carboxyl groups and low viscosity in the growing particles during the process of polymerization were important factors for partial growth.Part CIII of the series Studies on Suspension and Emulsion.     

Effect of protein content on the surface activity and viscosity of emulsan

Emulsan, produced byAcinetobacter calcoaceticus RAG-1, consists of a lipoheteropolysaccharide-protein complex. The amount of protein in the complex depends on the purification procedure. Maximum hexadecane-in-water emulsifying activity of emulsan was obtained with preparations containing 8–16 % protein. Neither deproteinized preparations (apoemulsan) nor protein-rich preparations emulsified hexadecane-in-water; however, mixtures of these preparations (containing 10–15 % total protein) were potent emulsifiers.Emulsifying activity was also obtained with a mixture of apoemulsan and polysaccharide-free emulsan protein. The stimulatory role of protein in the activity of emulsan was also demonstrated by pronase treatment of the complex. The presence of protein in the complex was important for lowering interfacial tension between hexadecane and water. Apoemulsan solutions showed _i values of 30 mN/m whereas, emulsan containing more than 6% protein showed values of 13–15 mN/m. Viscosity studies showed that: (i) The higher the protein content in the complex, the lower its intrinsic viscosity, indicating that association of protein with the polysaccharide backbone results in less extended conformation; (ii) the complex appears to be stable between 30 ° and 80 °C; and (iii) mixtures of apoemulsan and emulsan had intrinsic viscosities close to the value predicted from addition of the weight-fraction contribution of the individual components. The synergistic emulsifying activity of emulsan mixtures is explained in terms of surface tension lowering by the protein component and formation of stable interfacial films by the high molecular weight polysaccharide component.Preliminary results of this work were presented at the 5th International Conference on Surface and Colloid Science, Potsdam, N.Y., June 1985.     

Surfactant-free emulsion polymerization of styrene using crosslinked seed particles

The aim of this research was to prepare a monodisperse polystyrene latex without surfactants adsorbed at the particle surface. Conventional polymerization formulations usually lead to large amounts of oligomers. Furthermore, they are characterized by a low reproducibility with respect to particle size. This was overcome by using a seed latex that was crosslinked in order to overcome dissolution in the monomer phase. By adjusting the seed concentration, any desired particle size in the range 0.5–1.2 m could be obtained. The monodispersity was very good.