Ionic Stabilizer Research Articles

A new diagnostic instrument and method for stabilization of heaving soil in the beds of structures

Information regarding the development of new instruments for the laboratory testing of soil for frost heaving, and also results of experimental investigations to reduce the heaving properties of clayey soil under the action of an ionic stabilizer are cited.

Controlled synthesis of PDDA stabilized Au–Pd bimetallic nanostructures and their activity in hydrogenation of acetylene

Pd hydrosol was synthesized by reducing PdCl2 solution with dissolved H2 in the presence of PDDA [poly(diallyldimethylammonium chloride)] as ionic stabilizer. O2 treatment resulted in the reappearance of ligand to metal charge transfer bands of PdCl 4 2− . Repeated oxidation and hydrogen treatments caused aggregation/agglomeration of the Pd particles yielding big spherical aggregates of 30–50 nm but still keeping the size of the 5–6 nm primary particles. Aggregation was attributed to the reduction of PdCl 4 2− anion having high local densities around Pd particles surrounded by PDDA polycation. Au–Pd bimetallic hydrosols were synthesized by reduction with 2-propanol and by pulse radiolysis technique in the presence of PDDA. Both reduction modes synthesize Au core–Pd shell structures. The mode of reduction was observed to affect the particle size and the thickness of the Au core and Pd shell. At the Au rich samples the differences in the optical spectra were attributed to different dispersions of the Au–Pd particles. Au–Pd bimetallic hydrosols were adsorbed on Aerosil 200 and the supported samples were tested in gas phase hydrogenation of acetylene.

The effect of type of organic phase solvents on the particle size of poly( d,l-lactide-co-glycolide) nanoparticles

Poly( d,l-lactide-co-glycolide) (PLGA) nanoparticles were prepared by an emulsification-diffusion method. To investigate the effect of type of organic phase solvents on the mean particle sizes of obtained PLGA nanoparticles, different organic solvents [ethyl acetate (EA), propylene carbonate (PC), acetone (ACE), and dichloromethane (DCM)] were used with several stabilizers [didodecyl dimethyl ammonium bromide (DMAB), poly(vinyl alcohol) (PVA), and Pluronic F68]. The particle size of nanoparticles was observed by the dynamic light scattering method and atomic force microscopy (AFM). When DMAB, an ionic stabilizer, was used, small PLGA nanoparticles below 70 nm were obtained for EA and PC as partially water-soluble organic solvents, while large PLGA nanoparticles above 290 nm were prepared for ACE and DCM as a fully water-soluble solvent and a water-immiscible solvent, respectively. However, when PVA or Pluronic F68, non-ionic stabilizers, were used, a big difference in mean particle sizes between partially water-soluble solvent or fully water-soluble solvent and water-immiscible solvent was not observed, and all particles showed a large mean diameter above 110 nm, irrespective of the type of organic phase solvents.

Mechanisms of Soil Stabilization with Liquid Ionic Stabilizer

Numerous commercial suppliers are marketing liquid chemical products for stabilizing pavement subgrade and base soils. These nontraditional chemical stabilizers may offer viable alternatives for stabilizing sulfate-rich soils where conventional lime or cement treatment can lead to excessive soil expansion. Typically sold as concentrated liquids that are diluted in water before application, these products may be less expensive to use than lime or cement. However, many transportation agencies are hesitant to specify nontraditional liquid stabilizers without better information on the stabilizing mechanisms and documented field experiences. To identify the mechanisms associated with one class of these products, a representative ionic soil stabilizer and a sodium montmorillonite clay were selected for a detailed physical-chemical study. Laboratory testing included chromatography, spectroscopy, X-ray diffraction, electron microscopy, and standard titration analyses. These tests have shown that the principal active constituents of the selected ionic stabilizer are d-limonene (a by-product of citrus processing) and sulfuric acid, which react to form a concentrated, low-pH solution of sulfonated limonene. The observed changes in clay chemistry following treatment indicated that this product would stabilize a soil by altering the clay lattice. The result is the formation of a more highly weathered, less-expansive clay structure. On the basis of this understanding of the underlying mechanisms, ionic stabilizers applied at sufficiently high application mass ratios may improve the properties of certain soils on some highway construction projects.

Mono- or narrow disperse poly(methacrylate-co-divinylbenzene) microspheres by precipitation polymerization

Precipitation copolymerizations of five mono-vinyl methacrylic monomers including methyl methacrylate (MMA), butyl methacrylate (BMA), dodecyl methacrylate (DMA), glycidyl methacrylate (GMA), and hydroxyethyl methacrylate (HEMA) with divinylbenzene (DVB), in a wide range of comonomer composition, were carried out in acetonitrile to form mono- or narrow disperse crosslinked copolymer microspheres. In addition, two divinyl methacrylic monomers, ethylene glycol dimethacrylate (EGDMA) and triethylene glycol dimethacrylate (TEGDMA), were also copolymerized with DVB, and optionally a third comonomer (GMA or HEMA), to yield similar microspheres in acetonitrile. The possibility of creating porosity was explored for some of the copolymer particles. All these microspheres have clean surfaces due to the absence of any added steric or ionic stabilizer, and they are in the size of the micrometer range, varying from 1 to 7 µm, depending on the type and content of the methacrylic comonomer. Particle size distribution, surface morphology, internal texture, and porosity properties of these particles were studied by a Coulter Multisizer, a scanning electron microscope, a transmission electron microscope, and an Autosorb-1. The effects of comonomers on microsphere formation and morphology are described. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2899–2907, 1999