Search results for " stability."
showing 10 items of 1315 documents
Polymere acroleine, I. Mitt. Untersuchungen über die polymerisation des acroleins.
1955
Unter der Einwirkung typischer Polymerisations-Katalysatoren wie z. B. Azoisobuttersaurenitril, Peroxyde, Redox-Systeme, metallorganische Verbindungen und Friedel-Crafts-Katalysatoren geht Acrolein in polymere Produkte uber. Deren physikalische Eigenschaften (thermische Bestandigkeit, Viskositat der Losungen u. a.) hangen von den Polymerisationsbedingungen ab. Einige der erhaltenen polymeren Produkte unterscheiden sich deutlich von den bisher bekannten Polyacroleinen. By the action of typical catalysts of polymerisation (e.g. azo-bis-isobutyronitrile, peroxides, redox-systems, organometallic compounds, Friedel-Crafts-catalysts) acrolein forms polymeric products. The physical properties of s…
Cyclopolymerisation einiger glutardialdehyde. Struktur der polymeren
1962
Die loslichen Spontanpolymerisate des Glutardialdehyds, β-Methyl- und β-Phenylglutardialdehyds bestehen auf Grund ihrer Eigenschaften und IR-Spektren vornehmlich aus Tetrahydropyranstruktureinheiten, die durch eine Cyclopolymerisation gebildet werden. Es wird ein infrarotspektroskopischer Vergleich mit verschiedenen niedermolekularen Tetrahydropyran-Modellsubstanzen durchgefuhrt. Die unkatalysierte Polymerisation last sich infrarotspektroskopisch verfolgen. Die Poly-glutardialdehyde konnen acetyliert werden. Die Polymeren erfahren durch die Acetylierung eine wesentliche thermische Stabilisierung. Die Eigenschaften und IR-Spektren der Spontanpolymerisate werden mit denen des vernetzten Poly-…
Mass spectrometric investigation of polymers: Thermal degradation of truxillic and truxinic polyamides
1975
The thermal degradation mechanism of four isomeric truxillic and truxinic polyamides were investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation reactions were followed directly by this method by detecting the thermal and electron impact-induced fragments. The results obtained have shown that the thermal degradation products are sensibly different for the head-to-head (hh) and head-to-tail (ht) polymers and that the predominant pyrolytic process is the cyclobutane ring cleavage. In the hh isomers, both symmetrical and asymmetrical cyclobutane ring cleavage was detected, while in the ht isomers only symmetrical cleavage occurs; this explains the notice…
Synthesis and Characterization of Extended Bis(terpyridine)ruthenium Amino Acids
2009
(Oligopyridine)ruthenium(II) complexes have been widely used in dye sensitized solar cells and other sophisticated optical devices due to their outstanding photophysical properties and their chemical stability. Herein, we describe the longitudinal extension of our previously reported bis(terpyridine)ruthenium(II) amino acid [Ru(tpy–NH2)(tpy–COOH)]2+ (tpy = 4′-substituted 2,2′:6′,2″-terpyridine) by insertion of para-phenylene spacers –C6H4– between the terpyridine and the functional groups. The influence of the para-phenylene spacer on the absorption and emission properties is investigated using UV/Vis absorption and emission spectroscopy and is discussed within a qualitative molecular orbit…
Synthesis and Properties of Some Simple Organotitanium Compounds
1986
Before embarking on a detailed discussion of the titanation of carbanions, synthetic and physical organic aspects of several typical organotitanium (IV) compounds shall be surveyed, including thermal stability, aggregation state, X-ray structural data and bond energies. Some of this information is useful in understanding reactivity and selectivity in reactions with organic substrates. Low valent Ti (II) and Ti (III) shall be mentioned only on passing; the interested reader is referred to reviews [1].
Macrocycles as Molecular Units to Build up Electroresponsive Materials: A Comparative Theoretical Investigation of the Electronic and Optical Propert…
1990
Besides their classical and well-known applications as, e.g., dyes, pigments, catalysts, etc. [1], phthalocyanines (Pc’s) have been of particular interest in many fields of basic and applied research concerning solar cells [2], photosensitizers [3], low dimensional metals [4], gas sensors [5], electrochromism [6], Langmuir-Blodgett (LB) films [7], and nonlinear optics [8]. As an example, gas sensors [9], electronic devices [10], laser recording materials [11], and photovoltaic cells [12] can now be built from LB films of phthalocyanines. This great variety of interesting applications results from a number of unique properties that phthalocyanines exhibit On the one hand, they show an except…
Properties of the Nafion membrane impregnated with hydroxyl ammonium based ionic liquids
2012
In this work, the Nafion 112 membrane impregnated with nine various hydroxyl ammonium based ionic liquids have been investigated. The used ionic liquids were combined from hydroxyl ammonium cations (2-hydroxyethylammonium/HEA, bis(2- hydroxyethyl)ammonium/BHEA, tris(2-hydroxyethyl)ammonium/THEA) and carboxylate anions (formate, acetate, lactate). The membranes are characterized by conductivity and thermal stability measurements. It was found, that almost all composites have 10 times higher ion conductivity than a pure Nafion 112 at 90 ?C in ambient environment due to the higher thermal stability. The thermal stability of Nafion membrane was increased by all studied nine ionic liquids. In th…
Über die thermische stabilität von copolymeren des 1,3,5-trioxans. 26. Mitt. über polyoxymethylene1
1965
Die thermischen Eigenschaften von Copolymeren aus Trioxan und cyclischen Athern, cyclischen Acetalen, Lactonen oder Vinylmonomeren werden erortert. Die Copolymeren haben zwar meist etwas niedrigere Schmelztemperaturen als homopolymeres Polyoxymethylen; sie depolymerisieren jedoch im Gegensatz zu reinen Polyoxymethylendiolen beim Erhtitzen auf 200°C nur partiell. Der thermisch stabile Antiel der Copolymeren wird Auser durch ihre Zusammensetzung vor allem durch ihren Polymerisationsgrad bestimmt. Die Entstehung von Endgruppen und ihr Einflus auf die thermische Stabilitat werden diskutiert. Thermal properties of copolymers of trioxane with cyclic ethers and acetals, lactones and vinyl monomers…
Die herstellung einiger gekennzeichneter, aliphatischer azoverbindungen und ihre anwendung als initiatoren der polymerisation
1970
Es wird die Herstellung von vier Azoverbindungen beschrieben, die sich zum Teil vom α.α′-Azo-(isobuttersaurenitril) ableiten. Zwei Verbindungen geben bei der Polymerisation von Methacrylsauremethylester und Styrol Endgruppen, die in den Polymeren photometrisch leicht zu bestimmen sind; fur eine wird gezeigt, das sie die Polymerisation von Styrol startet, ohne das storende Nebenreaktionen auftreten. Die beiden anderen Azoverbindungen sind wegen ihrer hohen Zersetzungspunkte geeignet, radikalische Polymerisationen bei hoheren Temperaturen auszulosen (160°C). The preparation of four derivatives of α.α′-azo-bis-isobutyronitrile is described. The polymerization of methylmethacrylate and styrene …
Increased conformational rigidity of humic substances by oxidative biomimetic catalysis
2005
A synthetic water-soluble meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrinate of iron(III) chloride, Fe(TDCPPS)Cl, was employed as a biomimetic catalyst in the oxidative coupling of terrestrial humic materials. High-performance size-exclusion chromatography (HPSEC), solid-state nuclear magnetic resonance (CPMAS-(13)C NMR), electron paramagnetic resonance (EPR), and diffuse reflectance infrared spectroscopy (DRIFT) were used to follow conformational and structural changes brought about in different humic materials by the oxidative coupling. Increase in apparent weight-average molecular weight (Mw(a)) occurred invariably for all humic substances with the oxidative polymerization catalyzed …