Vinyl Polymerization. 282. Vinyl Polymerization Initiated by Dimethylhydroxylamine-Titanous(lll) Chloride Redox System

Abstract

The polymerization of vinyl monomers initiated by dimethylhydroxylamine hydrochloride (DHA)-titanous(III) chloride redox system has been studied in water under a nitrogen atmosphere. In the polymerization of methyl methyacrylate (MMA) initiated by the above system, the rate of polymerization has been found to be proportional to [DHA]^0.5 for DHA concentrations of less than 2.06 × 10^?3 mole/liter, whereas at higher concentrations the rate tends to fall rapidly. The rate has also been found to be proportional to [Ti(m)] ^0.58 and to [MMA] ^1.0. The maximum rate of polymerization has been observed at a 1:1 molar ratio of DHA to Ti(III). The polymerization proceeded via a radical mechanism. The overall activation energy was estimated as 5.5 kcal/mole. It has been suggested that the reduction of dimethylhydroxylamine by titanous(III) chloride yields the dimethylamino radical, which initiates vinyl polymerization. An examination of the initiating capacity of the initiator system for the polymerization of some vinyl monomers has also been made.     

A numerical study on the formation of diffusion flame islands in a turbulent hydrogen jet lifted flame

This paper presents a numerical study on the formation of diffusion flame islands in a hydrogen jet lifted flame. A real size hydrogen jet lifted flame is numerically simulated by the DNS approach over a period of about 0.5 ms. The diameter of hydrogen injector is 2 mm, and the injection velocity is 680 m/s. The lifted flame is composed of a stable leading edge flame, a vigorously turbulent inner rich premixed flame, and a number of outer diffusion flame islands. The relatively long-term observation makes it possible to understand in detail the time-dependent flame behavior in rather large time scales, which are as large as the time scale of the leading edge flame unsteadiness. From the observation, the following three findings are obtained concerning the formation of diffusion flame islands. (1) A thin oxygen diffusion layer is developed along the outer boundary of the lifted flame, where the diffusion flame islands burn in a rather flat shape. (2) When a diffusion flame island comes into contact with the fluctuating inner rich premixed flame, combustion is intensified due to an increase in the hydrogen supply by molecular diffusion. This process also works for the production of the diffusion flame islands in the oxygen diffusion layer. (3) When a large unburned gas volume penetrates into the leading edge flame, the structure of the leading edge flame changes. In this transformation process, a diffusion flame island comes near the leading edge flame. The local deficiency of oxygen plays an important role in this production process.     

Non-Newtonian flow and normal stress phenomena in solutions of polystyrene in toluene

Summary Non-Newtonian flow and normal stress phenomena are studied with solutions of polystyrene in toluene with varying temperature, concentration and molecular weight.The temperature dependence of normal and shear stresses of a solution with fixed concentration can be described in terms of the shift factor,a _T , which is commonly used in the study of linear viscoelastic phenomena of polymeric systems.From the measurements of normal and shear stresses the elasticity contribution to flow behavior of polymer solution can be evaluated, and its dependences on concentration and molecular weight are discussed. Each of the tested solutions shows more or less non-Newtonian viscosity behavior, especially very strongly in solutions with high concentration and high molecular weight. And these solutions are mainly Hookean in shear, but non-Hookean character appears in solutions with high concentration and with rather low molecular weight.The zeroshear viscosityversus concentration relationship is found to obey ac ⁵-dependence in a certain range of concentration, while in the same concentration range the reciprocal of steady shear compliance shows ac ^1,5 c ²-dependence. The zeroshear viscosityversus molecular weight relationship of solutions at a fixed concentration obeys the well-knownM ^3,4-dependence above a certain critical value of molecular weight which is dependent on the concentration. While the reciprocal of compliance is almost independent of molecular weight above this value, and it seems to be somewhat affected by the type of polymers such as molecular weight heterogeneity and/or degree of branching of the polymer.

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Zusammenfassung Nicht-Newtonsches Fließen und Normalspannungsphänomene wurden an Lösungen von Polystyrol in Toluol bei verschiedenen Temperaturen und Konzentrationen sowie bei verschiedenem Molekulargewicht untersucht.Die Temperaturabhängigkeit der Normal- und Schubspannungen einer Lösung bestimmter Konzentration kann durch den Schift-Faktora _T , der allgemein bei der Betrachtung linearer viskoelastischer Phänomene polymerer Systeme gebraucht wird, beschrieben werden. Aus den Messungen der Normal- und Schubspannungen wurde der Elastizitätsbeitrag zu dem Fließverhalten der polymeren Lösung abgeleitet und seine Abhängigkeit von der Konzentration und dem Molekulargewicht diskutiert.Jede der geprüften Lösungen zeigte mehr oder weniger nicht-Newtonsches Viskositätsverhalten, besonders stark ausgeprägt in Lösungen mit hoher Konzentration und hohem Molekulargewicht. Die Lösungen zeigten bei Scherbeanspruchung hauptsächlichHookeschen Charakter. Der nicht-Hookesche Charakter trat eher auf in Lösungen mit hoher Konzentration und bei niedrigerem Molekulargewicht.Die Anfangsviskositäts-Konzentrationsbeziehunggehorcht einerc ⁵-Abhängigkeit in einem gewissen Konzentrationsbereich, während bei derselben Konzentration der reziproke Wert der Komplianz (Nachgiebigkeit) bei stationärem Scheren einec ^1,5- bisc ²-Abhängigkeit aufweist. Oberhalb eines gewissen kritischen Wertes des Molekulargewichts, der von der Konzentration abhängt, gilt die bekannteM ^3,4-Beziehung zwischen der Anfangsviskosität und dem Molekulargewicht.Der reziproke Wert der Komplianz (Nachgiebigkeit) hängt fast nicht von dem Molekulargewicht oberhalb eines kritischen Wertes ab, aber das scheint durch den Typ der polymeren Substanz, wie Polymolekularität oder durch den Verzweigungsgrad, beeinflußt zu sein.

     

Utility of parallel-plate plastometer for rheological study of filled polymer melts

Summary In order to test the applicability of the parallel-plate plastometer to the rheological study of filled polymer melts, viscous properties of polyethylene and polystyrene filled with particles and short fibers were measured by this apparatus. Flow curves in the low range of shear rate were obtained by approximating the materials as Ostwald-de-Waele liquids. Up to about 0.5 of the volume fraction of the filler,, there was no problem and the utility of the apparatus was clearly shown. When increased more, the results were not necessarily self-consistent because the flow became unstable. Experiments on samples with high showed that the unstable flow resulted in an apparent yield stress which agreed with that estimated from the Casson's plots.

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Zusammenfassung Um die Anwendbarkeit des Parallel-Platten-Plastometers für die rheologische Untersuchung von Schmelzen gefüllter Polymerer zu prüfen, wurden mit einem solchen Gerät die viskosen Eigenschaften von Polyäthylen und Polystyrol-Proben gemessen, die mit Teilchen oder kurzen Fasern gefüllt waren. Im Bereich niedriger Schergeschwindigkeiten ließen sich die Fließkurven mit Hilfe der Ostwald-de Waele-Gleichung approximieren. Bis zu einer Füllstoff-Volumenkonzentration von etwa 50% traten keine Komplikationen auf, so daß die Eignung des Geräts für diese Fälle klar erwiesen werden konnte. Wenn jedoch noch weiter gesteigert wurde, waren die Ergebnisse durchweg nicht mehr widerspruchsfrei, da dann der Fließvorgang instabil wurde. Versuche mit hohen Volumenkonzentrationen zeigten, daß die Fließinstabilität eine scheinbare Fließgrenze zur Folge hat, deren Größe mit dem aus einer Casson-Darstellung abgeschätzten Wert in etwa übereinstimmt.

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With 8 figures and 1 table     

Insight into chemical mechanisms of sepal color development and variation in hydrangea

Hydrangea (Hydrangea macrophylla) is a unique flower because it is composed of sepals rather than true petals that have the ability to change color. In the early 20th century, it was known that soil acidity and Al³⁺ content could intensify the blue hue of the sepals. In the mid-20th century, the anthocyanin component 3-O-glucosyldelphinidin (1) and the copigment components 5-O-caffeoylquinic, 5-O-p-coumaroylquinic, and 3-O-caffeoylquinic acids (2–4) were reported. Interestingly, all hydrangea colors from red to purple to blue are produced by the same organic components. We were interested in this phenomenon and the chemical mechanisms underlying hydrangea color variation. In this review, we summarize our recent studies on the chemical mechanisms underlying hydrangea sepal color development, including the structure of the blue complex, transporters involved in accumulation of aluminum ion (Al³⁺), and distribution of the blue complex and aluminum ions in living sepal tissue.     

A Quantum Algorithm for a FULL Adder Operation Based on Registers of the CPU in a Quantum-gated Computer

International Journal of Theoretical Physics - So far, the world of quantum-gated computing has been exploited, aimed at the limited applications based upon the Deutsch algorithm in 1985 and a few...     

DNA-templated assembly of naphthalenediimide arrays

π-Stacked naphthalenediimide (NDI) arrays are of interest as charge-transport materials. We have designed and synthesized an NDI derivative with two Zn(II)-cyclens that act as receptors for the thymine base in DNA. UV/Vis and CD spectroscopy, gel filtration, and molecular-modeling studies have shown that the bis(Zn(II)-cyclen)-NDI can be assembled in the presence of oligo-dT to form π-stacked NDI arrays. The assembly of the NDI arrays was found to be dependent on the length of the oligo-dT and the temperature. The NDI-oligo-dT assembly on a gold substrate exhibits photocurrent responses due to electron transfer through the π-stacked array.     

Extraction-spectrophotometric determination of trace iron (II) in sea water with 2-[2-(3,5-dibromopyridyl)azo]-5-diethylaminobenzoic acid

An extraction-spectrophotometric method is described for the determination of traces of iron(II) with 2-[2-(3,5-dibromopyridyl)azo]-5-diethyl-aminobenzoic acid. The reagent forms a stable and blue 12 iron/reagent complex that can be extracted into chloroform. The apparent molar absorptivity of the iron(II) complex is 1.09 × 10⁵ 1 mol^–1 cm^–1 at 624 nm in chloroform. The reagent is relatively selective; interferences from cobalt, copper, nickel and vanadium can be removed by using dimethylglyoxime and EDTA. The method is applied to the determination of iron (II) in sea water and aluminium alloys with good precision and accuracy.     

Dielectric studies on the dynamics of polymer chains in various environments

Stockmayer's type-A chain such as cis-polyisoprene (PI) having dipole moments aligned parallel to the chain contour exhibits slow dielectric response, reflecting fluctuation of the end-to-end vector of the chain ( dielectric normal modes ). This article intends to review our own work on dielectric spectroscopy using PI as a probe for studying dynamics of large scale motion of the probe chain in binary blends with polybutadiene (PB) and in block copolymers with PB or with polystyrene. Through such studies we were able to see the features of polymer chain dynamics in various environments: Rouse-Zimm-like dynamics in overlapping-but-unentangled regimes, reptation with and without accompanying constraint release, behaviour of a subchain incorporated into block copolymers with miscible segments, and dynamics of polymer brushes in strongly segregating block copolymers in bulk and in solutions.