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Living Polymerization (live + polymerization)

Distribution by Scientific Domains
Polymers and Materials Science66%

Selected Abstracts

Effect of Solvents on Living Polymerization of Propylene with [t -BuNSiMe2Flu]TiMe2 -MMAO Catalyst System

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 3 2004
Kei Nishii
Abstract Summary: Batchwise polymerization of propylene was conducted at 0,°C in heptane using [tert -BuNSiMe2Flu]TiMe2 (1) combined with dried methylaluminoxane (MAO) and dried modified methylaluminoxane (MMAO), which were prepared from the toluene solutions of MAO and MMAO by removing the solvent and the free trialkylaluminium. The dried MMAO system quantitatively gave the polymer with higher molecular weight and narrower molecular weight distribution (MWD), ca. 1.3, compared with the dried MAO system. In addition, the polymerization with dried MMAO in toluene, chlorobenzene (CB) and ortho -dichlorobenzene (o -DCB), as solvent, also produced polymers quantitatively with MWD of ca. 1.1,1.3. The number-average molecular weight () of the polymers, obtained with these systems, increased linearly against the polymer yield, while the narrow MWD was retained and the number of polymer chains was almost constant. The results of post-polymerization in heptane and o -DCB proved that the living polymerization proceeded irrespective of the solvent used. The semi-batch polymerizations under an atmospheric pressure of propylene indicated that the propagation rate was more than 10 times higher in o -DCB than in heptane. The 13C NMR analysis of the polymers indicated that the syndiotacticity also depended on the polarity of the solvent and increased in the following order: CB,,,o -DCB,<,toluene,<,heptane. A plausible scheme for the interaction between active species and solvents. [source]

Rigid Crosslinked Polyacrylamide Monoliths with Well-Defined Macropores Synthesized by Living Polymerization

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 12 2009
Joji Hasegawa
Abstract Rigid crosslinked polyacrylamide monoliths with well-defined macropores have been successfully fabricated by organotellurium-mediated living radical polymerization (TERP) accompanied by spinodal decomposition. The TERP forms homogeneous networks derived from N,N -methylenebis(acrylamide) (BIS), in which spinodal decomposition is induced to form macropores. Macropore diameter can be controlled from submicrons to a few microns, and also the obtained networks contain mesopores in the macroporous skeletons, which are collapsed by evaporative drying. They are promising materials with hydrophilic polyacrylamide surfaces and have enough strength to preserve the macropores from the surface tension arising in the repetitive swelling and drying that may occur in many applications. [source]

New Strategy Targeting Well-Defined Polymethylene- block -Polystyrene Copolymers: The Combination of Living Polymerization of Ylides and Atom Transfer Radical Polymerization

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 7 2009
Jian-Zhuang Chen
Abstract Well-defined polymethylene- block -polystyrene (PM- b -PS) diblock copolymers were synthesized via a combination of living polymerization of ylides and atom transfer radical polymerization (ATRP) of styrene. A series of hydroxyl-terminated polymethylenes (PM-OHs) with different molecular weight and narrow molecular weight distribution were prepared using living polymerization of ylides following efficient oxidation in a quantitive functionality. Then, the macroinitiators (PM-MIs (,=,1,900,15,000; PDI,=,1.12,1.23)) transformed from PM-OHs in ,,100% conversion initiated ATRPs of styrene to construct PM- b -PS copolymers. The GPC traces indicated the successful extension of PS segment ( of PM- b -PS,=,5,000,41,800; PDI,=,1.08,1.23). Such copolymers were characterized by 1H NMR and DSC. [source]

Single-Mode Microwave Ovens as New Reaction Devices: Accelerating the Living Polymerization of 2-Ethyl-2-Oxazoline

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 22 2004
Frank Wiesbrock
Abstract Summary: The ring-opening cationic polymerization of 2-ethyl-2-oxazoline was performed in a single-mode microwave reactor as the first example of a microwave-assisted living polymerization. The observed increase in reaction rates by a factor of 350 (6 h,,,1 min) in the range from 80 to 190,°C could be attributed solely to a temperature effect as was clearly shown by control experiments and the determined activation energy. Because of the homogenous microwave irradiation, the polymerization could be performed in bulk or with drastically reduced solvent ratios (green chemistry). Monomer conversion, represented by the ratio ln{[M0]/[Mt]}, plotted against time for six temperatures in the range from 80 to 180,°C, and polymerization reaction vials, showing an increase in yellow color for those reactions performed (well) above and below 140,°C, indicating side reactions. [source]

High-Molecular-Weight Poly(vinylphosphonate)s by Single-Component Living Polymerization Initiated by Rare-Earth-Metal Complexes,

ANGEWANDTE CHEMIE, Issue 20 2010

Übertragbar: Auf einem Gruppentransferpolymerisations(GTP)-Mechanismus beruht die lebende Polymerisation von Diethylvinylphosphonat zu Homo- und Copolymeren mit hohen Molekulargewichten in Gegenwart einfacher Seltenerdmetall-Komplexe (siehe Schema). Dieser Mechanismus, der dem etablierten Mechanismus für polare Monomere wie Acrylate entspricht, öffnet einen neuen Zugang zu phosphorhaltigen Polymeren. [source]

Controlled and Living Polymerizations.

ANGEWANDTE CHEMIE, Issue 7 2010
From Mechanisms to Applications.
Wiley-VCH, Weinheim 2009. 612,S., geb., 149.00,,.,ISBN 978-3527324927 [source]