Richard E. Partch

Conducting polymer composites. I, Surface-induced polymerization of pyrrole on iron(III) and cerium(IV) oxide particles

Abstract Electrically conducting polypyrrole coatings on inorganic cores were obtained by deposition of pyrrole on catalytically active particles. The finely dispersed core materials were hematite (polyhedral and spindle-type), silica coated with hematite, and cerium(IV) oxide. The degree of polymer coverage could be controlled by varying the aging time and the properties of the carrier particles. The so prepared coated powders were examined by transmission electron microscopy and further characterized by elemental and thermogravimetric analyses, as well as by electrophoresis, X-ray diffraction, and conductivity measurements. The conductivities were comparable to those reported for pure polypyrrole and they increased with pressure.

Preparation of polymer colloids by chemical reactions in aerosols. III. Polyurea and mixed polyurea-metal oxide particles☆☆☆

Abstract Polyurea colloids consisting of spherical particles of narrow size distribution were prepared by reacting aerosol droplets of toluene diisocyanate (TDI) or hexamethylene diisocyanate (HDI) with ethylenediamine (EDA) vapor. The particle size could be altered by the temperature of the aerosol generator and by the flow rate of the carrier gas. Mixed polyurea/metal oxide particles were obtained by exposing the polymer colloid to alkoxide vapors with subsequent hydrolysis in a humid atmosphere. In this study titanium(IV) isopropoxide was used to prepare polyurea/TiO2 solids and aluminum secbutoxide for polyurea/Al2O3 powders. Experimental evidence indicates that the metal oxides are incorporated in the polymer beads rather than to form a surface layer.

Preparation of uniform spherical titania particles coated with polyurea by the aerosol technique

Abstract The aerosol technique has been employed in the preparation of uniform colloidal inorganic particles coated with an organic polymer. Specifically, spherical titania cores were produced first by hydrolysis of Ti(IV) ethoxide droplets in contact with water vapor. Hexamethylenediisocyanate liquid was then condensed on these particles and exposed to ethylenediamine vapor. By varying experimental conditions (temperature and flow rate) one attained uniform coatings of polyurea of different thickness on titania.

Preparation of polymer colloids by chemical reactions in aerosols: II. Large particles

Abstract Polymer and copolymer colloids have been prepared in modal diameters up to 30 μm by reacting aerosol droplets of styrene or “divinylbenzene” (which was a mixture of ortho, meta, and para isomers with ethylvinylbenzene) with the vapor of trifluoromethanesulfonic acid in a specially designed generator. The properties of the resulting particles (size distribution and surface characteristics) depend on the temperatures of the boiler and of the reaction chamber as well as on the monomer-to-initiator mass ratio.

Preparation of uniform colloidal dispersions by chemical reactions in aerosols IV. Mixed silica/titania particles

Abstract Spherical particles of mixed silica/titania composition were prepared by hydrolysis of aerosols consisting of titanium (IV) ethoxide and silicon (IV) chloride. Vapor of the latter was absorbed into preformed droplets of the alkoxide, the size of which could be controlled by changing the temperature and the flow rate of the carrier gas through the apparatus containing the two reagents. These droplets were then exposed to water vapor. The resulting amorphous mixed silica/titania particle were of a narrow size distribution, easily dispersed in water, with an isoelectric point at pH 7.1 ± 0.1. Heating at high temperature resulted in crystallization. ESCA measurements indicated an enrichment of titanium atoms on the surface, while atomic absorption analysis showed higher silicon concentration in the bulk phase. Light scattering data gave refractive index between that of SiO 2 and TiO 2 . BET surface areas suggested that the original colloidal particles were porous.

Microencapsulation of oil droplets by aerosol techniques—I. Metal oxide coatings

Abstract The solubility and reactivity of titanium and aluminum alkoxides in dodecane, diesel oil and distillation fractions of the latter are reported. When solutions of alkoxide in oil are nebulized and the thus formed droplets reacted with water vapor, metal oxide microcapsules form around the oil solvent and have morphologies and porosities dependent on reaction conditions.

Silver coating of spindle- and filament-type magnetic particles for conductive adhesive applications

Spindle-type hematite and magnetite particles and nickel filaments have been coated uniformly with silver by using chemical reduction. The effects of the reaction time and the concentration and nature of the reducing agent on the particle coatings were investigated at constant temperature. The reaction time had a pronounced effect on the nature of the coated surface layer. Coated and core particles were examined by scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDAX). The electrical properties of the particles were also characterized. The conductivity of nickel filaments which can be oriented under a magnetic field for anisotropic electric conduction increased from 302 to 877 S/cm at 3.5 kPa pressure when coated with silver.

Scavenging nanoparticles: an emerging treatment for local anesthetic toxicity.

e i o t g s a r i n a r i d t o t o r t c dreaded complication of local anesthetic use in regional anesthesia is systemic toxicity from nintentional intravascular local anesthetic injecion. Although systemic toxic reactions are not ommon after peripheral nerve block, 7.5 to 20 vents per 10, 000 in adults,1 they can be lifehreatening and resistant to treatment.2-6 Recent ata from an American Society of Anesthesiology losed Claims Project demonstrate that unintenional intravenous local anesthetic injection was the econd largest category of block-related regional nesthesia claims that resulted in death or brain amage.7 The manifestations of local anesthetic toxicity ange from local neurotoxic and myotoxic reactions o cardiovascular collapse and coma. Central nerous system toxicity presents as a spectrum that ncludes shivering, muscle twitching, tonic-clonic eizures, hypoventilation, and respiratory arrest.8 ardiovascular toxicity primarily manifests as arhythmias and myocardial depression.9-14 Local ansthetic overdose can cause a variety of arrhythias, including atrial and ventricular conduction elays, complete heart block, asystole, ventricular ctopy, ventricular tachycardia, torsades de pointes, nd ventricular fibrillation.8,15 The molecular mechanisms whereby local aneshetics exert their toxic effects have not been fully stablished and are likely complex in nature. Ex-

Aerosol and solution modification of particle-polymer interfaces

Abstract In recent years several investigators have focused on the synthesis of uniformly and continuously coated particles to impart improved chemical stability, mechanical strength, morphology and/or dispersibility to powders required for preparing next-generation composities. This paper reviews two in situ reaction methods employed at Clarkson University to selectively coat individual particles having widely different shape, size and chemical composition. The aerosol procedure allows core particles to become coated using room temperature liquid-gas reactions. Alternatively, coating particles dispersed in a solvent containing reactive precursors is more applicable to industrial processing. Uniform, well-adhering coatings of polyurea on titania powder, of polydivinylbenzene on silica beads, and of carbon and boron nitride on silicon carbide whiskers were made by selecting the correct precursors and reaction chemistries. Qualitative assessment of adhesion between the coatings and cores is given.

Preparation of uniform colloidal dispersions by chemical reactions in aerosols. VI: Silica-titania composite particles

Spherical silica/titania particles were prepared by nebulizing with a nozzle liquid mixtures of tetraethyl orthosilicate (TEOS) and titanium(IV) ethoxide [Ti(OEt)4] and contacting the resulting droplets with water vapor. The size distribution of the liquid aerosols was improved by mechanically eliminating the larger droplets and by the evaporation and condensation of the remaining droplets in the presence of AgCl nuclei introduced with the carrier gas. The composition of the resulting solids differed from that expected from the original liquids. Furthermore, the particles were not internally homogeneous; the surface layers contained a higher molar ratio of titania than the bulk. The electrokinetic data corroborated the surface composition. On calcination at 700°C, the titania component crystallized to anatase in the originally amorphous particles.