Search results for "polystyrene"
showing 10 items of 349 documents
UV-photometrische analyse kationisch erzeugter polystyrole, 1. Nachweis des covalenten einbaus von acylresten aus aromatischen acylperchloraten
1983
Polymerization of styrene was found not to take place with 4-phenylazobenzoyl perchlorate in benzene solution. 4-Biphenylcarbonyl perchlorate, however, initiates styrene polymerization under the same conditions leading to a product not containing acyl groups as indicated by UV spectroscopic analysis. 4-Phenylazobenzoyl, 2-naphthoyl, and 9,10-dioxo-2-anthracenecarbonyl perchlorate (6b, 7b, and 8b), prepared form silver perchlorate and the corresponding acyl chlorides 6a, 7a, and 8a in styrene, were found to initiate the polymerization of styrene under anhydrous conditions at −25°C in the dark. By UV spectroscopy it could be shown that the resulting polymers contain covalently bound acyl grou…
Gelchromatographie. 1. Mitt. Trennung von oligomeren
1966
Vernetzte Polymere werden hergestellt und ihre Eignung zur gelchromatographischen Trennung von Gemischen von Oligomeren gepruft; im einzelnen wurden untersucht: mit Isocyanaten modifiziertes Sephadex; Polymethyl-und Polybutylmethacrylat, vernetzt mit Glykoldimethacrylat bzw. mit Polyathylenoxid-dimethacrylat; Polyvinylacetat, vernetzt mit n-Butandioldivinylather; Polystrol, vernetzt mit Divinylbenzol; ferner Silicagel. Der Einflus der Molekulgestalt auf das Elutionsvolumen wurde gepruft. Die Elutionsvolumina von p-Oligophenylenen, die eine stabchenformige Molekulgestalt besitzen, sind groser als die von Oligourethanen gleichen Molekulargewichts; o- und m-gewinkelte Oligophenylene zeigen geg…
1976
1981
Elution curves on spherosil gels in pure and mixed eluents of poly(dimethylsiloxane), PDMS, and poly(methyl methacrylate), PMMA, as well as those of polystyrene, PS, just for comparison, have been determined. In a general way, PDMS elution volumers fit to those of PS, whereas PMMA elution curves shift to higher retention volumes. The differences in retention volumes between the different polymeric solutes have been interpreted in terms of differences in polymer-gel and polymer-solvent interactions. Hydrogen-bonding seems to be the main contribution to solute-substrate interactions.
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.
1984
An apparatus is presented for the precise measurement of vapour pressures. It is tested with diethyl ether and applied to the system tert-butyle acetate/polystyrene (weight-average molecular weight Mw = 110000) up to polymer concentrations of ca. 60 wt.-% in the temperature range from 10 to 90°C; by means of the Redlich-Kister equation the results can well be described analytically. The data are evaluated to yield the Flory-Huggins parameter in the subsequent article in conjunction with other experimental information.
Bulk morphologies of polystyrene-block-polybutadiene-block-poly(tert-butyl methacrylate) triblock terpolymers
2015
Abstract The self-assembly of block copolymers in the bulk phase enables the formation of complex nanostructures with sub 100 nm periodicities and long-range order, both relevant for nanotechnology applications. Here, we map the bulk phase behavior of polystyrene-block-polybutadiene-block-poly(tert-butyl methacrylate) (SBT) triblock terpolymers on a series of narrowly distributed polymers with widely different block volume fractions, ϕS, ϕB and ϕT. In dependence of ϕ, we find the lamella–lamella, core-shell cylinder, cylinder-in-lamella and core-shell gyroid morphology, but also a rarely observed cylinder-in-lamella phase. The bulk morphologies are thoroughly characterized by transmission e…
Fast Response Heating Module for Temperature Programmed GC Analysis in Microreaction Systems
2000
For monitoring the reactant and product concentrations of a gas phase microreactor for ethylene oxide synthesis the development of a miniaturised device for fast GC analysis suitable for operation in conjunction with the microreactor is advantageous. Therefore, a method employing short (0.2 – 0.4 m) packed capillary columns was developed. Highly crosslinked polystyrene microspheres proved to be the most suitable adsorbent enabling a high separation efficiency. For fast temperature programming design concepts for an efficient heating module capable to be used with short capillary columns were developed. In principle, planar as well as cylindrical designs are suitable for integration of a res…
ChemInform Abstract: Hydrophobically Directed Aldol Reactions: Polystyrene-Supported L-Proline as a Recyclable Catalyst for Direct Asymmetric Aldol R…
2008
A simple synthetic methodology for the preparation of a polystyrene-supported L-proline material is reported, and this material has been used as catalyst in direct asymmetric aldol reactions between several ketones and arylaldehydes to furnish aldol products in high yields and stereoselectivities. Screening of solvents showed that these reactions take place only in the presence of water or methanol, at lower levels of conversion in the latter case. This solvent effect, coupled with the observed high stereoselectivities, has been explained in terms of the formation of a hydrophobic core in the inner surface of the resin, whereas the hydrophilic proline moiety lies at the resin/water interfac…