Search results for "Polystyrene"
showing 10 items of 349 documents
From Spherical Mesopores to Worm-Shaped Mesopores : Morphology Transition in Titania–Polystyrene-b-poly(ethylene oxide) Composite Films with Increasi…
2013
A morphology transition from spherical mesopores to worm-shaped mesopores within titania block copolymer composite thin films has been observed by varying the sol–gel reaction time from 40 min to 48 h in the four-component templating system of polystyrene-$\mathit{b}$-poly(ethylene oxide) (PS-$\mathit{b}$-PEO), 1,4-dioxane, concentrated HCl, and titanium tetraisopropoxide (TTIP) with a PS-$\mathit{b}$-PEO mass concentration of 0.25 wt.-%. The impact of the sol–gel reaction time on the local structure, long-range lateral structure, and vertical structure of the as-prepared, calcined, and UV-degraded thin films as well as the structural changes in solution have been systematically investigate…
Size Dependence of Tracer Diffusion in Supercooled Liquids
1996
We have determined by forced Rayleigh scattering the diffusion coefficients D of several photochromic tracers with van der Waals radii between 0.38 and 8 nm (the largest ones being photolabeled polystyrene micronetworks) in 10 glass-forming liquids at temperatures between the glass temperature Tg and ∼1.2Tg. The results were analyzed in terms of power law plots, D(T) ∝ T/η(T)ξ, where η is the solvent shear viscosity, and temperature shifts, D(T) ∝ T/η(T + ΔT). The shift ΔT was related with the width of the rotational correlation time distribution via the time−temperature superposition principle.
Phase-distribution chromatography (PDC) of polystyrene
1970
A chromatographic technique is described where the stationary phase is a layer of a very high molecular polystyrene fraction (M = 107) on glass beads (ballotines). The mobile phase is cyclohexane passing the column at a constant temperature below the theta-temperature. A polystyrene sample of sufficiently low molecular weight (M ≤ 106) injected as a small plug at the top of the column is fractionated because the distribution between the mobile and the stationary phase depends on the molecular weight. Since the large molecules preferentially remain in the stationary phase, the smaller molecules leave the column first. The fractionation effect is inverse to that found in GPC experiments. The …
Porous fractal gels: secondary effects in SEC
1992
Abstract The fractal nature of porous silica gels, Spherosil XOA 200 and of a Lichrospher mixture, has been tested through size exclusion chromatography of polystyrene in pure and mixed eluents. Fractal parameters, D f and L , depend on eluent with D f values close to 2.0 for Spherosil and higher than 2.0 for Lichrospher. D f and L changes with eluent have been related to secondary separation effects and partition and adsorption contributions have been evaluated.
Microporous hypercrosslinked polystyrene Styrosorb as a restricted access packing in sample clean-up for high performance liquid chromatography. Part…
1993
Styrosorb is a beaded microporous polystyrene with particle sizes between 2 and 4 μm. In spite of hypercrosslinkage the material was seen to swell in organic solvents. The native material is functionalized with Tris-groups at the outer surface of the particles. The average pore diameter was determined as 1.45±0.3 nm from size exclusion data using polystyrene and polyethylene standards in THF. The reversed phase behavior of the restricted access phase Styrosorb was investigated by injection of two test mixtures. Mixture I contained five aromatic amines, mixture II consisted of AmperozideR and four related compounds. The optimum range of mobile phase composition was assessed so that analytes …
Ionomers in solution: 1. Viscometric and chromatographic studies in cononsolvent and cosolvent mixtures
1997
Abstract The viscosity and elution behaviour of polystyrene sulfonate ionomers with varying ionic content has been studied in the pure solvents chloroform (CHL), tetrahydrofuran (THF), dioxan (DIO), ethyl acetate (EA) and dimethylformamide (DMF) as well as in their cononsolvent mixtures CHL/THF (50:50), DIO/CHL (75:25) and in the cosolvent mixture EA/DMF (50:50). In the pure solvents with low dielectric constant the reduced viscosities of ionomers are lower at low concentrations and higher at moderate ones than the respective viscosities of the polystyrene precursor. These results can be explained by formation of intramolecular and intermolecular associations. Moreover, differences in visco…
Reversed-phase high-performance liquid chromatography of proteins and polypeptides on polystyrene-coated silica supports
1990
Abstract A new type of hydrolytically stable reversed-phase packing material prepared by multi-point covalent binding of polystyrene chains onto the surface of porous silica was examined in the high-performance liquid chromatography of proteins and polypeptides. Whereas wide-pore material was shown to give a rapid and efficient resolution of proteins, packings with smaller pores provided better selectivities for peptides.
Influence of oscillating main flow on separation efficiency in asymmetrical flow field-flow fractionation.
2021
The steadily rising interest in the investigation of interactions between nanomaterials and biological media has also led to an increasing interest in asymmetrical flow field-flow fractionation (AF-FFF). The biggest strength of AF-FFF is the possibility to alter the flow profiles to suit a specific separation problem. In this paper, the influence of an oscillating main flow on the separation efficiency of AF-FFF is investigated. Such oscillations can e.g. be caused by the main pump To investigate the influence of such flow conditions on the separation efficiency in AF-FFF systematically, different oscillation profiles were applied and their influence on the elution profile and the retention…
Modelling the influence of nanoparticles in the phase behaviour of an epoxy/polystyrene mixture
2007
Abstract The cloud point temperatures of four series of epoxy/polystyrene blends have been experimentally determined as a function of polymer mass and system composition. The phase diagrams show an UCST behaviour, increasing incompatibility as the molar mass increases. The Flory–Huggins theory with a concentration-dependent interaction parameter has been developed to study the compatibility of two polymers in presence of spherical nanoparticles. This theory has been first compared with the experimental cloud point curve in absence of nanoparticles, and secondly it has been used to predict the thermodynamic behaviour in presence of different volume fraction of nanoparticles. Nanoparticles co…
Enhanced structural correlations accelerate diffusion in charge-stabilized colloidal suspensions
1999
Theoretical calculations for colloidal charge-stabilized and hard sphere suspensions show that hydrodynamic interactions yield a qualitatively different particle concentration dependence of the short-time self-diffusion coefficient. The effect, however, is numerically small and hardly accessible by conventional light scattering experiments. Applying multiple-scattering decorrelation equipment and a careful data analysis we show that the theoretical prediction for charged particles is in agreement with our experimental results from aqueous polystyrene latex suspensions.