Micron-sized,monodisperse, snowman/confetti-shaped polymer particles by seeded dispersion polymerization

Snowman/confetti-shaped, micron-sized, monodisperse composite particles were prepared by seeded dispersion polymerizations of n-butyl methacrylate (nBMA) with 1.28 and 2.67 m-sized polystyrene (PS) seed particles, respectively, in an ethanol/water (80/20, w/w) medium. These nonspherical composite particles consisted of one or several poly(nBMA) protuberances on the surfaces of the spherical PS particles.Part CCLXII of the series Studies on Suspension and Emulsion     

Preparation of micron-size monodisperse polymer particles by seeded polymerization utilizing the dynamic monomer swelling method

Utilizing a new type of monomer swelling method, 6.1 m-size monodisperse polymer particles were prepared by seeded polymerization. 1.8 m-size monodisperse polystyrene (PS) seed particles (1.8 m in size) were prepared by dispersion polymerization in ethanol-water (80/20, v/v) medium in the presence of poly(acrylic acid) as stabilizer with 2,2-azobisisobutyronitrile as initiator. The PS seed dispersion was mixed with ethanol-water (60/40, v/v) solution dissolving styrene (S) monomer, benzoyl peroxide as initiator, and poly(vinyl alcohol) as stabilizer. By slow, continuous, dropwise addition of water with a micro feeder into the mixture, the PS particles absorbed the many S monomers, which were separated from the medium and swelled from 1.8 m to 8.4 m while keeping the monodispersity high. We named this procedure the dynamic swelling method. Then, the seeded polymerization of the absorbed S monomer was carried out in the presence of NaNO₂ as water-solube inhibitor.Part CXXII of the series Studies on Suspension and Emulsion.     

Formation of multihollow structures in crosslinked composite polymer particles

Micron-size monodisperse polymer particles having multihollow structures were prepared as follows. First, micron-size monodisperse polystyrene/poly(styrene-divinylbenzene) (PS/P(S-DVB)) composite particles were produced by seeded copolymerization of S and DVB with 2,2-azobisisobutyronitrile as an initiator in the ethanol/water (76/24, weight ratio) medium in the presence of 2.37 m-size monodisperse PS seed particles produced by dispersion polymerization. The molar ratio of S/DVB was changed in the range of 1/110/1. The uncrosslinked polymer within the composite particles was extracted with toluene under reflux. For the highest DVB content (S/DVB=1/1, molar ratio), one large hollow was observed in a part of the composite particles after the extraction. For the middle DVB content (S/DVB=4/1, molar ratio), multihollow structure was observed in all the particles. For the lowest DVB content (S/DVB=10/1, molar ratio), fine multihollow structure was observed in all the particles.Part CXLIII of the series Studies on Suspension and Emulsion     

Preparation of micron-size monodisperse polymer microspheres having crosslinked structures and vinyl groups

Micron-size monodisperse polymer microspheres having crosslinked structures therein and vinyl groups thereon were prepared by seeded copolymerization of styrene and divinylbenzene with 2,2-azobisisobutyronitrile as initiator in ethanolwater medium in the presence of 2.1-m monodisperse polystyrene seed particles produced by dispersion polymerization. The optimum conditions of the seeded copolymerization for producing the microspheres with good monodispersity and colloidal stability were determined.Part CXXI of the series Studies on Suspension and Emulsion.     

Control of hollow size of micron-sized monodispersed polymer particles having a hollow structure

Micron-sized monodispersed cross-linked polymer particles having one hollow in the inside were produced by seeded polymerization for the dispersion of (toluene/divinylbenzene)-swollen PS particles prepared utilizing the dynamic swelling method which the authors proposed. In order to control the hollow size, the weight ratio of toluene/PS was changed in the range of 520. The hollow size increased with an increase in the weight ratio. Even if benzene and xylene were used in place of toluene, similar hollow particles were produced, though the hollow size was affected by their solubility in water.Part CLIII of the series Studies on Suspension and Emulsion     

Estimation of distribution of vinyl groups in micron-sized monodisperse polymer microspheres by bromine titration method

The distribution of vinyl groups in polystyrene/poly(styrene-divinylbenzene) (PS/P(S-DVB)) composite microspheres produced by seeded copolymerization of S and DVB in the presence of 2.1-m monodisperse PS seed particles was estimated from the amount detected with bromine titration method as a function of the reaction time under various conditions.Part CXXIII of the series Studies on Suspension and Emulsion.     

Production of submicron-size monodisperse polymer particles having aldehyde groups by the seeded aldol condensation polymerization of glutaraldehyde (II)

Submicron-size monodisperse polystyrene/polyglutaraldehyde (PS/PGLA) composite particles having aldehyde groups at the surfaces were produced by the seeded aldol condensation polymerization of glutaraldehyde at various temperatures of 040°C. Since a part of aldehyde groups was consumed by the Cannizzaro reaction (hemiacetal formation) as a intermolecular reaction of PGLA, the amount of aldehyde groups on PS/PGLA composite particles was varied by the competition between the aldol condensation reaction and the Cannizzaro reaction at the various temperatures.Part CXXXIX of the series Studies on Suspension and Emulsion     

General equation for dissociative heterolytic reaction rates and corrections to the Br?nsted relationship

A general equation is proposed for the rates of halide and H⁺ ion transfer. A relay-type participation of H₂O in the transfer of H⁺ in aqueous solutions is substantiated.

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: - H⁺. H₂O H⁺ .

     

Preparation of micron-size monodisperse polymer microspheres having chloromethyl group

Micron-size monodisperse polymer microspheres having chloromethyl groups thereon were prepared by two-step polymerization process as follows. First, micron-size monodisperse polystyrene particles were prepared by dispersion polymerization with 2,2-azobisisobutyronitrile as initiator in ethanol-water medium in the presence of poly(acrylic acid) as stabilizer under various conditions. Secondly, in the presence of the 1.9-m monodisperse polystyrene particles produced under the optimum conditions, seeded copolymerization for styrene and chloromethyl styrene was carried out. The seeded copolymerization proceeded smoothly without producing new particles, and it was confirmed by x-ray photoelectron spectroscopy that the chloromethyl group existed more at the surface of the produced microsphere than at that of film cast from the benzene solution in which the microspheres were dissolved.Part CVI of the series Studies on Suspension and Emulsion.     

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     

Synthesis of micron-sized, monodisperse polymer particles of disc-like and polyhedral shapes by seeded dispersion polymerization

Micron-sized, monodisperse polymer particles having unique disc-like and polyhedral shapes were produced by seeded dispersion polymerization of various methacrylates with 1.57 m-sized polystyrene seed particles in the presence of saturated hydrocarbon droplets in methanol/water. Such nonspherical shapes were controllable by the polymerization conditions.Part CCLX of the series Studies on Suspension and Emulsion     

New type of radical formation on the surface of Pd/Al2O3 by alkynes and allene

An interesting new class of radicals or paramagnetic species was obtained on the surface of active alumina (-type) supported palladium oxide by heating alkynes and allene with the catalyst.

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, , ( ), .

     

Formation mechanism of anomalous “golf ball-like” composite polymer particles by seeded emulsion polymerization

Recently, the authors found that anomalous polystyrene/polybutyl acrylate composite particles, whose surfaces had many dents, were produced by emulsifier-free seeded emulsion polymerization of butyl acrylate with polystyrene seed particles. Such a particle was named a golf ball-like particle. In this article, the morphology and the formation mechanism of the golf ball-like composite polymer particles were studied.Part CLV of the series Studies on Suspension and Emulsion     

Production of multihollow polymer particles by the stepwise alkali/acid method IV. Acid treatment process

The effects of pH, temperature and time in the acid-treatment process on the multihollow structure formed within submicron-sized monodispersed polymer particles by the stepwise alkali/acid method proposed by the authors were examined in detail. The original particles were produced by emulsifier-free emulsion terpolymerization of styrene, butyl acrylate, and methacrylic acid. It was clarified that the number and the size of hollows per particle were drastically changed by the acid treatment conditions as well as those in the alkali treatment process.Part CXLV of the series Studies on Suspension and Emulsion     

Production of submicron-size monodisperse polymer particles having aldehyde groups by seeded aldol condensation polymerization

Submicron-size monodisperse polystyrene/polyglutaraldehyde composite particles having aldehyde groups at the surfaces were produced by seeded aldol condensation polymerization of glutaraldehyde in the presence of polystyrene particles prepared by emulsifier-free emulsion polymerization. This technique is expected to be useful for the production of size-controlled polymer particles having aldehyde groups.Part CXXXVI of the series Studies on Suspension and Emulsion     

Cadmium induced changes of the metabolic activity of the freshwater snailPlanorbis corneus estimated by direct calorimetry

By use of f1ow-microcalorimetric studies the effect of cadmium in the sublethal concentration range (0.5-h LC_{5 0} is 1.69 mg/l) on the metabolic activity of the freshwater snailPlanorbis corneus was revealed. The high toxicity was confirmed by the change in the heat production rate (mean value is 453 W/g fresh weigth) in a cadmium perfusate down to a concentration of 0.01 g/l. The decrease in heat output depended on the cadmium concentration and amounted from 19% at 0.01 g/l to 88% at 1000 g/l. The microcalorimetric method proved to be a useful continuous-f1ow technique to assess qualitatively and quantitatively the toxic effects of cadmium on an aquatic organism already 4 hours after exposure.

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Zusammenfassung Mit Hilfe der Flow-Mikrokal orimetrie wurde die Uirkung von Cadmiumchlorid im subletalen Konzentrationsbereich auf die Stoffwechselaktivitat der SüwasserschneckeP1anorbis corneus untersucht. Die Wärmeproduktion der Tiere sank im Mittel von 435W/g Frischgewicht bei einer Cadmiumkonzentrat i on von 0.01 g/l auf 81Z und bei 1000 g/1 auf 19Z. Die Kalorimetrie eruies sich als eine nützliche Flow-Technik, mit der die Toxizität von Cadmium qualitativ und quantitativ bereits 4 Stunden nach der Exposition erfat werden kann.

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$ /LC₅₀=1,69 // planorbis corneus. $ / 453 / 0,01 /. 19% 0,01 / 88% 1000 /. , $ $ .

     

Investigation of the chemisorption of propylene on zinc oxide by temperature-programmed desorption

The interactions of propylene with zinc oxide have been studied by temperature-programmed desorption (TPD) under experimental conditions free of inter- or intraparticle limitations or readsorption phenomena.The results indicate that propylene is adsorbed on two types of active sites, and the Arrhenius parameters for the corresponding desorption processes have been calculated; moreover, on the basis of these results, important hypotheses can be made regarding the reaction mechanisms of the total oxidation and the dehydroaromatization of propylene on zinc oxide.The experiments confirm that thermal methods can be successfully used in the interesting and important field of heterogeneous catalysis.

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Zusammenfassung Die Wechselwirkungen von Propylen mit Zinkoxid wurden durch temperaturprogrammierte Desorption (TPD) unter Versuchsbedingungen frei von inter- oder intrapartikulären Begrenzungen oder Readsorptionserscheinungen untersucht.Die Ergebnisse zeigen, daß Propylen an zwei Typen von aktiven Stellen adsorbiert wird. Die Arrhenius-Parameter für die entsprechenden Desorptionsprozesse wurden berechnet. Aufgrund dieser Ergebnisse können wichtige Hypothesen bezüglich des Reaktionsmechanismus der totalen Oxidation und der Dehydroaromatisierung von Propylen an Zinkoxid aufgestellt werden.Die Versuche bestätigen, daß thermische Methoden auf dem interessanten und wichtigen Gebiet der heterogenen Katalyse mit Erfolg eingesetzt werden können.

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- , . , . . , . , .

     

On the determination of kinetic parameters through the peak temperature method for differential scanning calorimetry

A critical assessment of the so-called peak temperature methods (originally proposed by Kissinger) is presented. The two ingredients of peak temperature methods, namely, Kissinger's assumption and transformation equations, are considered. First it is argued that Kissinger's assumption although not being valid for DTA holds for DSC. Then it is shown that the only way to use kinetic parameters obtained from non-isothermal experimental data to describe both iso- and anisothermal kinetics is to take the same reaction rate equation for the two kinetics, as previously done by Henderson.

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Zusammenfassung Die ursprünglich von Kissinger vorgeschlagene sog. Peak temperatur-Methode wird einer kritischen überprüfung unterzogen. Die zwei Bestandteile dieser Methode, nÄmlich Kissinger's Annahme und die Transformationsgleichungen werden erörtert. ZunÄchst wird bewiesen, da\ Kissinger's Annahme, obzwar sie nicht für die DTA gültig ist, für die DSC zutrifft. Danach wird gezeigt, da\ die einzige Möglichkeit, von Daten nicht-isothermer Experimente kinetische Parameter zur Beschreibung sowohl einer isothermen als auch einer nicht-isothermen Kinetik zu erhalten, darin besteht, für beide kinetische FÄlle die gleiche Reaktionsgeschwindigkeitsgleichung anzunehmen, wie schon früher Henderson verfahren ist.

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, . : . , , . , , - , , .

     

Kinetics and mechanism of the oxidation of L-ascorbic acid by 2,6-dichlorophenol-indophenol in aqueous solution

The kinetics of oxidation of L-ascorbic acid by 2,6-dichlorophenolindophenol in aqueous solution has been studied. The rate of the reaction decreases with increasing pH since the hydrogen ascorbate ion is less reactive than the unionized L-ascorbic acid. The rate constants for the oxidation of the two species have been evaluated and a plausible mechanism of the reaction is suggested.

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L- 2,6-- . pH, , L- . .

     

Modelling of self-oscillations in the combustion of n-heptane-isooctane mixtures

A mathematical model has been constructed to describe the self-oscillation regime of the cool-flame combustion of an n-heptane-isooctane mixture. The character of the dependence of the amplitude and oscillation period on the temperature and mixture composition is in a qualitative agreement with the similar experimental data.

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