Search results for "TYR"

1980

Molecular weights of Trogamid T® were determined by ultracentrifugation, light-scattering, osmometry and viscometry, molecular weight distributions by gel permeation chromatography (GPC) and five different fractionation methods. The separation efficiency of GPC with N,N-dimethylformamide as solvent was tested with three different types of gels, crosslinked polystyrene, porous glass and crosslinked poly(vinyl acetate), the last one yielding the best results. Solution fractionations show better results than precipitation methods. All fractionations gave far too small apparent non-uniformities. After correction according to the non-uniformities of the fractions the results corresponded to thos…

Moleküldimensionen von polymeren in verschiedenen lösungsmitteln auf grund hydrodynamischer messungen

1960

Ein fraktioniertes Polystyrol vom Molekulargewicht Mw ≈ 540000 wurde in Chloroform, Toluol, Methylathylketon und Cyclohexan sowie in drei Mischungen von Toluol und Methylathylketon untersucht. Da das Chloroform ein gutes, das Cyclohexan dagegen ein Θ-Losungsmittel fur Polystyrol darstellt, nehmen die Dimensionen des Fadenmolekuls beim Ubergang zwischen den Losungsmitteln ab. Mit den Knaueldimensionen andern sich Reibung und Viskositat des Polystyrols. Messungen der Sedimentationskonstanten, der Diffusionskonstanten, der Viskositatszahl sowie der Dichte und der Zahigkeit fur die gemischten Losungsmittel wurden ausgefuhrt. Die Ergebnisse der Messungen werden benutzt, um aus der Viskositatsthe…

Rheological studies of moderately concentrated polystyrene solutions in the vicinity of the θ temperature. II. Shear-rate dependence for different th…

1983

The viscosity data of moderately concentrated polystyrene solutions in trans-decalin (TD) (θ solvent, θ temperature 21°C) and toluene (TL) (good solvent) reported in Part I are discussed in terms of Graessley's entanglement theory. Under good solvent conditions, Graessley's master curve provides an excellent fit up to high shear rates, whereas in the vicinity of the θ conditions the data have to be modified by a parameter ηfric introduced by Ito and Shishido. The characteristic time of mechanical response to flow of chains approximately given by the shift factor τ0 is found in good solvents to be on the order of the Rouse relaxation time. In poor solvents, close to demixing, τ0 tends to muc…

Phase Distribution Chromatography (PDC) of Polystyrene

1971

Abstract Phase distribution chromatography is a new chromatographic method of fractionating polymers. The separation is achieved by partitioning the sample between the solvent and a polymer phase, in the case a noncross-linked polystyrene of very high molecular weight, which is coated as a thin layer on small glass beads. The temperature must be held below the θ-temperature of the sample. The separation increases sharply with decreasing temperature. The theory of this method is presented and compared with experimental results. The agreement is very good.

The kinetics of anionic polymerization of styrene in 1,2-dimethoxiethane

2007

Kinetic measurements in a flow apparatus in combination with conductance measurements, permit the determination of the two equilibrium constants Kes and Kdiss* and the three propagation rate constants k(±)c, k(±)s and k(−) as a function of temperature. The great differences in the polymerization rate in various solvents are mainly caused by their influence on the equilibrium constants. The influence of the solvent on the rate constants is not greater than in other chemical reactions.

Zur polymerisation und copolymerisation des natriumvinylsulfonats

1959

Natriumvinylsulfonat (VS-Na) zeigt in konzentrierten wasrigen Losungen eine ausgepragte Polymerisationsneigung. Die Polymerisationsgeschwindigkeit und der erreichte Umsatz hangen stark von der Aciditat der Losungen ab. Es wurde gefunden, das mit der Polymerisationsdauer und mit wachsendem Umsatz auch die Molekulargewichte der Polymerisate ansteigen. Wasserunlosliche oder nur begrenzt losliche ungesattigte Verbindungen wie Styrol, Vinylacetat und andere konnen in Dimethylsulfoxyd in homogener Losung mit VS-Na copolymerisiert werden. Sodiumvinylsulphonate (VS-Na) shows a strong tendency for polymerization in concentrated aqueous solutions. The rate of polymerization and the conversion depend …

Die thermische diffusion von polystyrol in verschiedenen lösungsmitteln

1969

Es wird uber Messungen von thermischen Diffusionskoeffizienten und LUDWIG-SORET-Koeffizienten von Polystyrol in den Losungsmitteln Toluol, Methylathylketon, Butylacetat und Cyclohexan berichtet. Es zeigte sich, das der rein thermisch bedingte Diffusionsprozes in Butylacetat und im Θ-Losungsmittel Cyclohexan unabhangig vom Molekulargewicht ist, wie as fur Toluol bereits fruher nachgewiesen werden konnte. Fur Methylathylketon wurde eine schwache, aber deutliche Abhangigkeit von D' vom Molekulargewicht zu D' ∼ M−0,12 gefunden. Bemerkenswerterweise verhalten sich die beiden in Bezug auf Polystyrol thermodynamisch sehr ahnlichen Losungsmittel Butylacetat und Methylathylketon in dieser Hinsicht s…

Polystyrene-supported organocatalysts for α-selenenylation and Michael reactions

2011

Abstract Three different resin-supported catalysts have been prepared by using the well established post-modification approach by means of thiol-ene coupling reaction. Two catalysts were tested for the first time in the asymmetric α-selenenylation of propanal, while the third catalyst was used in the Michael addition reaction. While the preliminary results are not encouraging in the case of supported Jorgensen’ catalyst, interesting data have been collected with both for the supported MacMillan and prolyl-prolinol catalysts. In fact, these catalysts displayed good activity and selectivity. A reversed enantioselectivity in the α-selenenylation was observed by changing the polarity of the sol…

Anwendung der gelchromatographie auf cellulosenitrate

1970

Es wird uber gelchromatographische Untersuchungen von Cellulosenitrat und Polymethylmethacrylat in Aceton als Losungsmittel berichtet. Das gunstigste Trennverhalten fur die Fadenmolekule sehr grosen Durchmessers wurde mit hochvernetzten fur Aceton gepackten Styrolgelen erzielt. Als universelle Trennparameter versagten die in Tetrahydrofuran haufig anwendbaren Kombinationen von [η] und M. Am besten stimmen noch die mittels Lichtstreuung gemessenen Tragheitsradien als Funktion des Elutionsvolumens fur die beiden Polymeren uberein. Gelchromatographic measurements of cellulosenitrate and polymethylmethacrylate in the solvent acetone are reported. For coiled molecules of very large diameters hig…

Cardiovascular Damage Induced by Anti-VEGF Therapy

2018

Vascular endothelial growth factor (VEGF) plays an important role in maintaining the regular homeostasis of vascular walls. VEGF binds its receptor (VEGFR) promoting the regular survival and function of endothelial cells. Anti-VEGF and anti-VEGFR drugs inhibit the action of VEGF and VEGFR. These drugs can cause cardiovascular toxic effects such as arterial hypertension, thromboembolism, myocardial ischemia and heart failure. The monoclonal antibody bevacizumab and tyrosine kinase inhibitors (sorafenib, sunitinib, pazopanib, regorafenib, axitinib, cabozantinib, ponatinib) are the main inhibitors of VEGF, VEGFR and other tyrosine kinases. In this chapter we will illustrate the cardiovascular …