Search results for "toluene"

Rheological studies of moderately concentrated polystyrene solutions. I. A new method for the extrapolation of the zero-shear viscosity

1983

Measurements of the viscosity coefficient η of solutions of polystyrene (Mw = 6.0 × 105 and 1.77 × 106) in trans-decalin (TD, θ solvent) and toluene (TL, good solvent) as function of shear rate (11−104 s−1), concentration (4.24−11.21 wt %), and temperature (10–50°C) are reported. As a new theoretically grounded method for the determination of the zero-shear viscosity η0 it is proposed to plot η as a function of . The intercepts of the straight lines obtained by this procedure give η0 in good agreement with directly measured values.

An experimental investigation of the nonlinear refractive index (n2) of carbon disulfide and toluene by spectral shearing interferometry and z-scan t…

2003

International audience; The recently proposed spectral shear interferometry and the well-known z-scan techniques were employed for the determination of the nonlinear refractive index n2 of CS2, toluene and fused silica. The determined n2 values by both techniques were found to be in very good agreement. In addition, the role of the repetition rate of the laser is also investigated revealing its importance for the correct determination of both the size and the sign of the nonlinearity.

Diffusiosmessungen an polymeren in lösung mittels tracer-technik

2007

A cell for measuring coefficients of diffusion and self-diffusion by tracer techniques is described. The cell consists of two Teflon disks and is of the rotational shearing type. The amount of polymer is minimal (about 0.1 ml. for both components). Labeled and unlabeled fractionated polymethacrylate of identical molecular weight distribution was used to determine diffusion coefficients in benzene and toluene. The classical optical measurement is impossible, for these solvents exhibit a refraction index very close to that of polymethacrylate. In acetone, where optical as well as tracer techniques are applicable, the measured diffusion coefficients of the two methods are in good agreement. Al…

1993

The viscosities of moderately concentrated solutions of poly(butyl methacrylate)—Mw = 1820 kg/mol–in the thermodynamically good solvent toluene and in the theta solvent 2-propanol were measured up to pressures of 2000 bar as a function of shear rate in the temperature interval from 40 to 70°C. Both systems obey Graessley's equation so that it is possible to obtain the following rheological parameters in addition to the zero-shear viscosity η0 from the dependences . η can be split into an entanglement part ηent plus a frictional contribution ηfric, and the characteristic viscometric relaxation time τ0 becomes accessible. The present results demonstrate that the application of pressure raises…

Nanostructured Polymer Brushes With Reversibly Changing Properties

2002

AbstractWe investigated the interplay between different mechanisms of the lateral and vertical segregation in the synthesized via “grafting from” approach symmetric A/B (where A and B are poly(styrene-co-2,3,4,5,6-pentafluorostyrene) and poly(methylmethacrylate), respectively) polymer brushes upon exposure to different solvents. We used X-ray photoemission electron spectroscopy and microscopy (X-PEEM), AFM, water contact angle measurements, and oxygen plasma etching to study morphology of the brushes. The ripple morphology after toluene (nonselective solvent) revealed elongated lamellar-like domains of A and B polymers alternating across the surface. The dimple-A morphology consisting of ro…

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…

Heterogeneous Gold Catalyst: Synthesis, Characterization, and Application in 1,4-Addition of Boronic Acids to Enones

2015

The new 1 wt % Au/TiO2–UVM-7 catalyst was prepared and fully characterized. This heterogeneous catalyst proved to be active, selective and recyclable for the unprecedented gold-catalyzed 1,4-addition of various functionalized arylboronic acids to 2-cyclohexen-1-one and other selected enones using toluene as a solvent. The gold-based catalyst was recycled two times and played an active role in this reaction, and the nature of the solvent determined a remarkable change in the products’ selectivities.

Partielle spezifische refraktionen von polymethylmethacrylat und polystyrol. I. Einfluß verschiedener lösungsmittel

1969

Auf der Grundlage der Formeln von LORENTZ-LORENZ, GLADSTONE-DALE und EYKMAN wurden die partiellen spezifischen Refraktionen von Polymethylmethacrylat in den Losungsmitteln Aceton, Athylacetat, Butylacetat, Tetrahydrofuran, Dioxan, Chloroform, Toluol und Benzol sowie die von Polystyrol in Butanon, Dioxan, Toluol und Benzol bestimmt. Es zeigt sich, das these Werte, die mit einer Genauigkeit von ± 0,1% aus den experimentellen Grosen Brechungsindex-Inkrement, Brechungsindex der Losung und partielles spezifisches Volumen berechnet wurden, nicht ganz frei von Losungsmitteleinflussen sind. Der groste Unterschied wurde bei den LORENTZ-LORENZ-Refraktionen gefunden und betrug 1,3%. Die EYKMAN-Refrakt…

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…