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Size-exclusion chromatography with light scattering detection experiments conducted on poly(acrylic acid) neutralized to different degrees or using hydroxides with different counterions suggest that the same counterion and degree of neutralization is observed at the detector, irrespective of salt concentration, degree of neutralization and counterion at the time of injection. This strongly supports that during the chromatographic experiment the counterions of the polyelectrolyte are exchanged with those of the eluent, resulting in an effective dialysis of the polyelectrolyte solution during the size-exclusion chromatography experiment. Consequently, the refractive index increment determined by a refractive index detector equals the refractive index increment obtained after excessive dialysis against the pure eluent. Therefore, the species detected and characterized by light scattering coupled to size-exclusion chromatography are not identical to the species injected into the chromatographic system. Despite this structural change during the chromatographic experiments, the correct molar mass for the injected species is obtained by size-exclusion chromatography with light scattering detection. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Kiliaris P.,National Technical University of Athens | Papaspyrides C.D.,National Technical University of Athens | Xalter R.,BASF | Pfaendner R.,Deutsches Kunststoff - Institute
Polymer Degradation and Stability | Year: 2012

In this study, the flame retardancy and physical properties of polyamide 6, melt processed in a twin-screw extruder with various amounts of melamine polyphosphate and layered silicates, were examined. Generally, there were indications that exfoliated nanocomposites were produced. During compounding, the presence of layered silicates was found to result in polymer degradation, which was further enhanced by the addition of the flame retardant. The additives were also shown to restrain the ability of polyamide 6 for crystallization. Tensile modulus and tensile strength were substantially improved, however polymer's ductility deteriorated. The incorporation of the additives exerted a positive effect also on the flame retardancy of polyamide 6, leading to materials of UL94 V-2 classification. © 2012 Elsevier Ltd. All rights reserved. Source


Bashir M.A.,Deutsches Kunststoff - Institute | Radke W.,Deutsches Kunststoff - Institute
Journal of Chromatography A | Year: 2012

The retention behavior of a range of statistical poly(styrene/ethylacrylate) copolymers is investigated, in order to determine the possibility to predict retention volumes of these copolymers based on a suitable chromatographic retention model. It was found that the composition of elution in gradient chromatography of the copolymers is closely related to the eluent composition at which, in isocratic chromatography, the transition from elution in adsorption to exclusion mode occurs. For homopolymers this transition takes place at a critical eluent composition at which the molar mass dependence of elution volume vanishes. Thus, similar critical eluent compositions can be defined for statistical copolymers. The existence of a critical eluent composition is further supported by the narrower peak width, indicating that the broad molar mass distribution of the samples does not contribute to the retention volume. It is shown that the existing retention model for homopolymers allows for correct quantitative predictions of retention volumes based on only three appropriate initial experiments. The selection of these initial experiments involves a gradient run and two isocratic experiments, one at the composition of elution calculated from first gradient run and second at a slightly higher eluent strength. © 2011 Elsevier B.V.. Source


Finlayson C.E.,University of Cambridge | Spahn P.,Deutsches Kunststoff - Institute | Snoswell D.R.E.,University of Cambridge | Yates G.,University of Cambridge | And 4 more authors.
Advanced Materials | Year: 2011

Permanent ordering of sub-micrometer polymeric spheres by edge rotational shearing is reported. The resulting high-quality, bulk, 3D-ordered polymer opal thin-films exhibit strikingly intense, tuneable structural color, which is applicable for photonics, metamaterials, nanoassembly, and structural color applications Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Schollenberger M.,Deutsches Kunststoff - Institute | Radke W.,Deutsches Kunststoff - Institute
Polymer | Year: 2011

A new approach to gradient chromatography of polymers is presented, in which the sample is introduced at the end of the gradient and elutes within the elution volume range typical for size exclusion chromatography (SEC). Due to the gradient the samples are retarded and elute nearly independent of molar mass at the adsorption threshold. The concept was proven for a series of narrowly distributed poly(methy methacrylate)s (PMMA) in a chloroform-tetrahydrofuran (THF) SEC-gradient. The application of the SEC-gradient to a blend of PMMA and polystyrene standards of similar molar masses, which could not be separated by SEC due to their similar hydrodynamic sizes, resulted in a clear separation according to chemical composition. Since SEC-gradients allow dissolving the sample in strong eluents, which might result in breakthrough peaks in conventional gradients, the new approach is a valuable alternative to conventional gradient chromatography. © 2011 Elsevier Ltd. All rights reserved. Source

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