Chromophore Quench Labeling: Simulated Snapshots of Molar Mass Distributions for the Rapid Mechanistic Analysis of Catalytic Alkene Polymerization

The differences between the QELSS and classical diffusion coefficient of a polydisperse polymer resulting from distinct definitions of experimentally accessible average values are calculated for two assumed specific forms of molar mass distributions. Predicted deviations are compared with the experiment using NBS 706 standard polystyrene. QELSS Dz of this sample relates within 2-4% to the classical diffusion coefficient, if the Schulz-Zimm molar mass distribution is assumed to be valid. In general, differences between the height-area and QELSS diffusion coefficient of about 20% may be found for Mw/Mn ~ 2, and this value may increase above 35%, if strongly tailing molar mass distribution pertains to the sample.

Download Full-text

An improved algorithm for calculating relaxation time spectra from material functions of polymers with monodisperse and bimodal molar mass distributions

Rheologica Acta ◽

10.1007/bf00367154 ◽

1995 ◽

Vol 34 (4) ◽

pp. 397-405 ◽

Cited By ~ 18

Author(s):

Christoph J. Brabec ◽

Alois Schausberger

Keyword(s):

Relaxation Time ◽

Molar Mass ◽

Mass Distributions ◽

Material Functions ◽

Improved Algorithm

Download Full-text

Determination of molar mass distributions of poly(methacrylates) in the analytical ultracentrifuge with schlieren and UV optics

Makromolekulare Chemie Macromolecular Symposia ◽

10.1002/masy.19920610114 ◽

1992 ◽

Vol 61 (1) ◽

pp. 176-184 ◽

Cited By ~ 4

Author(s):

Bernhard Ortlepp ◽

Dietrich Panke

Keyword(s):

Molar Mass ◽

Analytical Ultracentrifuge ◽

Mass Distributions

Download Full-text

Effect of PEEK degradation on commingled fabrics consolidation

10.25518/esaform21.1985 ◽

2021 ◽

Author(s):

Lisa Feuillerat ◽

Olivier De Almeida ◽

Jean-Charles Fontanier ◽

Fabrice Schmidt

Keyword(s):

Melt Spinning ◽

Molar Mass ◽

Degradation Kinetics ◽

Gel Permeation Chromatography ◽

Raw Material ◽

High Porosity ◽

Absorption Bands ◽

Mass Distributions ◽

Key Factor ◽

Lower Molar

The effects of PEEK degradation on consolidation of commingled semi-finished products have been investigated. Two commingled semi-finished products provided by two different suppliers have been studied and compared to a powdered fabric based on the same PEEK grade. Both were manufactured from aligned AS4 carbon and PEEK yarns but the first product referred as the NCF1 has a lower commingling level than the second one identified as the NCF2. Contrary to what could be expected, under the same processing conditions, consolidation of the NCF1 and the NCF2 systematically results in a high porosity content, above 10%. Fourier Transform Infrared spectrophotometry (FTIR) in ATR mode and Gel Permeation Chromatography (GPC) have shown small molecular structure modifications of PEEK yarns compared to the raw material, such as a shift of molar mass distributions towards lower molar mass and the appearance of C-H absorption bands attributed to non-aromatic alkanes. These modifications have been attributed to sizing of PEEK filament. Calorimetric (DSC) and rheological analyses have demonstrated that the presence of sizing in the semi-finished products have huge consequences on the degradation kinetics. The crystallization temperature decreases and the viscosity increases significantly. This acceleration of the degradation kinetics is the reason of the poor consolidation behavior during composite manufacturing. The conditions of melt spinning extrusion under which the neat PEEK is transformed into filament are therefore a key factor of PEEK degradation.

Download Full-text

Dinuclear Nickel(II) and Palladium(II) Complexes in Combination with Different Co-Catalysts as Highly Active Catalysts for the Vinyl/Addition Polymerization of Norbornene

Zeitschrift für Naturforschung B ◽

10.1515/znb-2003-1202 ◽

2003 ◽

Vol 58 (12) ◽

pp. 1152-1164 ◽

Cited By ~ 60

Author(s):

Vasile Lozana ◽

Paul-Gerhard Lassahn ◽

Cungen Zhang ◽

Biao Wu ◽

Christoph Janiak ◽

...

Keyword(s):

Molar Mass ◽

Active Species ◽

Schiff Base Ligands ◽

Coordination Polymerization ◽

Polymer Characterization ◽

Mass Distributions ◽

Molar Ratios ◽

Co Catalysts ◽

Highly Active ◽

Addition Polymerization

Dinuclear nickel(II) and palladium(II) complexes with Schiff-base ligands (derived form salicylaldehyde condensed with 2-amino-1-alcohols or from 2-hydroxy-5-methylisophthaldialdehyde and pyridine-2-carboxaldehyde condensed with semicarbazide, thiosemicarbazide, carbonodihydrazide, or thiocarbonodihydrazide) can be activated with the co-catalysts methylalumoxane (MAO) or tris(pentafluorophenyl)borane/triethylaluminium, B(C6F5)3/AlEt3 for the vinyl/addition polymerization of norbornene to reach activities of up to 2.4 · 107 gpolymer/mol(metal)·h (molar ratios metal:AlMAO = 1:100, metal:borane:AlEt3 = 1:9:10). Polymer characterization by GPC gave molar mass distributions of Mw/Mn ≈ 2, thereby indicating a coordination polymerization with a single-site character of the active species.

Download Full-text