Search results for "Polystyrene"

1,3,5-triisopropylbenzene diffusion in polystyrene solutions

1996

Self-diffusion coefficients of 1,3,5-triisopropylbenzene (TIB) in binary solutions with polystyrene and ternary mixtures comprised of TIB, toluene, and polystyrene have been measured by static gradient nuclear magnetic resonance (SG-NMR) techniques. These data, as well as mutual-diffusion coefficient data measured by capillary column inverse gas chromatography (CCIGC), have been analyzed here with the Vrentas-Duda free-volume diffusion model. Although both binary and ternary diffusion coefficient data can be accurately correlated with the model, the results contradict those of an earlier investigation, which suggested that TIB diffuses as a single unit in polystyrene solutions. The new data…

Optical characterization of polystyrene direct opals and of inverse-opal hydrogels

2012

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.

Improvement of the photo-stability of polystyrene-block-polybutadiene-block-polystyrene through carbon nanotubes

2015

Abstract The photo-stability of Polystyrene-Polybutadiene-Polystyrene (SBS) based nanocomposites containing bare multi-walled carbon nanotubes (CNTs) and carbon nanotubes bearing carboxylic functional groups (CNTs-COOH) in comparison to that of pristine SBS has been studied. The photo-oxidation of pristine SBS occurs through crosslinking reactions and oxidized species formation and both these processes begin at early stage of exposure. The formation of crosslinking, formerly in polybutadiene phase, assessed by spectroscopical (FTIR), mechanical, dynamic mechanical and rheological analysis, leads to occurrence of internal mechanical stresses in the solid state and the SBS samples become prem…

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.

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…