Search results for "Molar"

Die zweifache unterdrückung der polymerisation einiger bis(methacrylsäureester) mittels radikalischer additionsreaktionen

1973

Aus Hydrochinon, Resorcin, Dihydroxydiphenylen und Dihydroxynaphthalinen wurden mit Methacrylsaurechlorid Bis(methacrylsaureester) hergestellt. Setzte man diese in siedendem Benzol mit groser Verdunnung gelosten Ester dem Angriff von Radikalen aus α.α′-Azoisobuttersauredinitril (Primarradikale) aus, dessen Uberschus in Beziehung zum Ester mindestens zwanzigfach molar war, so erhielt man mittels saulenchromatographischer Trennung Verbindungen, bei denen je olefinische Doppelbindung zwei Primarradikale addiert waren (unterdruckte Polymerisation). Die Struktur dieser Produkte wurde mittels Elementaranalyse, Molekulargewichtsbestimmung, IR- und 1H-NMR-Spektren bewiesen. Demnach kann die Polymer…

1990

Taking into account the dependency on molar mass of the viscometric interaction parameter B, the modified Stockmayer-Fixman-Burchard equation ([η]/M1/2) = KΘ + C″ · A2 · M1/2 is obtained. It relates the intrinsic viscosity, [η], to the second virial coefficient, A2, and to the unperturbed dimensions parameter, KΘ, with C″ being a constant. Hereupon, KΘ can be determined from [η] and A2 data of any binary (solvent/polymer) and/or ternary (solvent 1/solvent 2/polymer) system, BPS and/or TPS. Because of the scarcity of reliable sets of [η] and A2 values mostly for TPS, the application of the above equation to obtain KΘ coefficients rests limited. This limitation can be surmounted by an A2 eval…

Enhanced polyurethanes based on different polycarbonatediols

2012

Segmented thermoplastic polyurethanes (PUs) were prepared from 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BD) and different macrodiols with a molar mass of 1000. Properties of those PUs based on polycarbonatediol (PCD) were compared with their homologous based on polyesterdiol and polyetherdiol as macrodiols. The proportion used in this study was macrodiol:BD:MDI = 1:2:3, in mole ratio. The hard segment weight percentage is 48 wt% for different PUs. Thermogravimetric analysis, differential scanning calorimetry, differential mechanical analysis, Fourier transform infrared-attenuated total reflection spectroscopy, as well as mechanical properties and retention on flexural prope…

1972

Different rates of initiation and propagation, e.g., in the case of living polymerization, lead to considerable deviations from a POISSON distribution. Using a bifunctional initiator the distribution obtained is composed of a single distribution and a coupled distribution. The maximum value of xw/xn never exceeds 1.4 even for a ratio kp/ki = 106. Verschiedene Start- und Wachstumsgeschwindigkeiten fuhren z. B. im Fall der lebenden Polymerisation zu erheblichen Abweichungen von einer POISSON-Verteilung. Die Verwendung eines bifunktionellen Initiators ergibt eine Verteilung, die sich aus einer einfachen und einer gekoppelten Verteilung zusammensetzt. Der Wert xw/xn uberschreitet nicht den Betr…

Die Bestimmung der Molekulargewichtsverteilung von nichtkristallisierenden Polymeren mit dem Elektronenmikroskop, 5. Bestimmung der Masse der Einzelm…

1977

A method is described for the determination of the molecular weight distribution (MWD) of various polymers from electron microscopy pictures of their molecules. It is shown, that the number of molecules needed to construct the distribution is between 200 and 300. Furthermore, with macroscopic density of the polymer and the volume determined by electron microscopy, the correct mass of a single molecule is obtained. The method is demonstrated for samples of polystyrene and poly(methyl methacrylate) and the results are compared with those of GPC-measurements.

Synthesis and thermoresponsive properties of four arm, amphiphilic poly(tert-butyl-glycidylether)-block-polyglycidol stars

2011

Abstract A series of four arm stars with copolymer arms composed of poly(tert-butyl-glycidylether)-b-polyglycidol were prepared using a multi-step process based on anionic ring-opening polymerization. Control of the length of the arms and the number of functional (hydroxyl) reactive groups was achieved by anionic polymerization. Stars with molar masses up to 12200 g/mol were prepared. The amphiphilic character of the star structure was varied using different polyglycidol block lengths. The star structure and molar mass of the obtained stars were characterized by SEC–MALLS and NMR spectroscopy. The temperature behavior of an aqueous solution of the obtained polymers was also investigated. Th…

(Co)polymerisation Behaviour of Supported Metallocene Catalysts: Carrier Effect

2006

The polymerisation and copolymerisation of ethylene with 1-hexene over metallocene catalysts L 2 ZrCl 2 / MAO (L = Cp, n-BuCp, t-BuCp, i-PrCp, Me 5 Cp) supported on different types of carriers (MgCl 2 (MeOH) 6 or silica with CH 3 surface groups obtained in the sol-gel process) were studied. It was demonstrated that both the metallocene structure and the type of inorganic support affected catalyst activity and polymer properties such as melting point, molecular weight and molecular weight distribution. The metallocene structure also determined comonomer incorporation, both for homogeneous and supported catalytic systems. When a catalyst is anchored on a support, it becomes less effective at …

1976

A radical mechanism is proposed for the formation of the 1,2-polymer 2 in the “spontaneous” polymerization of 4-vinylpyridinium salts 4-VP.HX (X=NO3, ClO4, HSO4, I) in aqueous solution on the basis of strong inhibition by oxygen and other radical inhibitors. Quantitative investigation of the influence of oxygen on the formation of the 1,2-polymer allowed the derivation of a formal kinetic scheme for the initiation and polymerization steps which is consistent with a free radical mechanism. Dependence of the average molecular weight of 2 on monomer concentration is in agreement with this model. Dependence of the inhibition time on the oxygen concentration as well as an acceleration of the fin…

Kristallisation und schmelzverhalten von fraktionen verzweigten polyethylens, 1. Darstellung und charakterisierung der fraktionen

1983

A branched polyethylene with broad molecular weight distribution was separated into a series of fractions by fractional precipitation from dilute solution. The fractions were characterized by viscometric and density measurements, IR-spectroscopy and calorimetry. The methyl group content and the density turned out as largely constant. Molecular weight effects show up in the melting behaviour. The main range of melting and the end of the melting curve shift to lower temperatures with decreasing molecular weight. Compared to the overall extension of the melting range these shifts are small. One has to conclude that polydispersity gives only a minor contribution to the broadening of the melting…

Stability of 11-Nor-Δ9-carboxy-tetrahydrocannabinol Glucuronide in Plasma and Urine Assessed by Liquid Chromatography-Tandem Mass Spectrometry

2002

Abstract Background: Unconjugated 11-nor-Δ9-carboxy-tetrahydrocannabinol (THCCOOH) in blood and urine has been proposed as a valuable marker, but the glucuronide (THCCOOglu) is present in considerably higher concentrations than the parent drug. Acyl glucuronides have been shown to be potentially reactive conjugates, which may affect the in vitro metabolite pattern. Methods: Extraction procedures and a liquid chromatography-tandem mass spectrometry assay were developed and validated to investigate the stability of THCCOOglu in urine and plasma. Plasma and urine samples with added THCCOOglu were stored at −20, 4, 20, and 40 °C up to 10 days. Results: The glucuronide was stable at −20 °C in bo…