Search results for "Methyl methacrylate"
showing 10 items of 162 documents
Mechanism of Anionic Polymerization of (Meth)acrylates in the Presence of Aluminium Alkyls IV. Formation of a Co-ordinative Polymer Network via the L…
1996
The polymerization of methyl methacrylate in the presence of aluminium alkyls in toluene deviates from conventional kinetics. This results predominantly from the formation and precipitation of a co-ordinative polymer gel or network. Due to the lower reactivity and accessibility of the living chains in the gel, they are regarded as ’dormant’ and thus the concentration of active species decreases during polymerization. The network formation occurs via co-ordination of the living aluminate chain end group with in-chain ester carbonyl groups. Part of the chains are deactivated by a termination process but they are free of cyclic β-ketoesters which would result from the common ’back-biting’ reac…
Die vielfältigen additionsprodukte von phenylen-, naphthylen-, biphenylylen- und methylendiphenylendimethacrylaten mit radikalen aus 2,2'-azoisobutyr…
1976
Die Reaktionen von Phenylen-, Naphthylen-, Biphenylylen- und Methylendiphenylendimethacrylaten (1–4) wurden teils mit 2,2'-Azoisobutyronitril (AIBN) in Substanz oder anionisch in Losung mit Butyllithium oder Natriumdihydronaphthylid (Naphthalinnatrium), teils mit grosem Uberschus an AIBN stark verdunnt in siedendem Benzol durchgefuhrt. Neben unloslichen (vernetzten) Polymeren wurden losliche erhalten, darunter Cyclopolymere vom Typ 9, wie die Ergebnisse der Hydrolyse und anschliesende Umsetzung mit Diazomethan zu Poly(methacrylsaure-methylester)n zeigten. Die Verdunnungsreaktion ergab die Produkte 5 der unterdruckten Polymerisation, der innermolekularen Addition mit Kopf/Schwanz- und Schwan…
Study of the molecular origin of the mechanical and dielectric β relaxation of methyl methacrylate/isopropenyl methyl ketone copolymers
1988
Resultats de l'etude dielectrique, mecanique et par TSC en faveur d'une combinaison d'une barriere intra- et intermoleculaire dans la relaxation beta
Pyrene Containing Polymers for the Non-Covalent Functionalization of Carbon Nanotubes
2009
Pyrene containing diblock copolymers based on poly(methyl methacrylate) were synthesized and investigated regarding their adsorption on carbon nanotubes (CNT). The pyrene units were introduced using a reactive ester monomer for the build up of the second block which later on was reacted polymer-analogously with amine functionalized pyrene derivatives. As we started from the same reactive ester intermediate, full block length identity is given. We varied the length of the anchor block to find an optimal block length and used pyren-1-yl-methylamine as well as 4-pyren-1-yl-butylamine as anchor units. For both anchor units a maximal adsorption was found for 13 and 20 anchor units, respectively.…
Cyclodextrins in polymer synthesis: polymerization of methyl methacrylate under atom-transfer conditions (ATRP) in aqueous solution
2000
Host guest complexes of methyl methacrylate (MMA) and randomly methylated β-cyclodextrin (m-β-CD, 1 a) were polymerized in aqueous medium using atom-transfer radical polymerization. Ethyl 2-bromoisobutyrate (EBIB) was used as an initiator, copper(I) bromide as the catalyst, and bipyridine (bipy) or 4,4′-di-(5-nonyl)-2,2´-bipyridine (dNbipy) as ligands. The unthreading of m-β-CD during the polymerization led to water-insoluble poly(methyl methacrylate) (PMMA). It was found that using dNbipy resulted in higher monomer conversion than using bipy as the ligand under similar conditions. Furthermore, it is shown that the polymerization of MMA under these conditions has a living character. The pol…
Tuning the upper critical solution temperature behavior of poly(methyl methacrylate) in aqueous ethanol by modification of an activated ester comonom…
2012
A statistical copolymer of methyl methacrylate (MMA) and pentafluorophenyl methacrylate (PFPMA, 6 mol%) exhibits upper critical solution temperature (UCST) behavior in aqueous ethanol solutions tunable by post-polymerization modification with different amines. The phase transition behavior of the obtained copolymers in aqueous ethanol was evaluated in detail. As expected, all copolymers reveal an upper critical solution temperature with 55 vol% or higher ethanol content. Furthermore, the solubility in aqueous ethanol of the copolymer can be increased by the introduction of hydrophilic moieties. When hydrophobic substituents are introduced a decrease in solubility was observed with low conte…
Estimation of Number-Average Molecular Weights of Copolymers by Gel Permeation Chromatography−Light Scattering
1996
The true number-average molecular weight, Mn, of copolymers is obtained by GPC coupled with a light-scattering detector even if the composition and therefore the refractive index increment varies with elution volume, provided slices taken are monodisperse with respect to molecular weight and composition. In contrast, only an apparent weight-average molecular weight, can be obtained by the conventional GPC−light scattering combination, even for a perfect chromatographic resolution. The errors in Mn associated with nonhomogeneous slices are estimated. Experimental data with mixtures of linear polystyrene and poly(methyl methacrylate) confirm these estimations and indicate that the error in Mn…
Mechanism of anionic polymerization of (meth)acrylates in the presence of aluminium alkyls, 2. Kinetic investigations with methyl methacrylate in tol…
1995
The kinetics of the polymerization of methyl methacrylate initiated by lithium alkyls (tert-butyllithium or ethyl α-lithiobutyrate) was investigated in the presence of aluminium alkyls (triethylaluminium or triisobutylaluminium) in toluene at −78°C. The rate of polymerization decreases considerably once the living dimer is formed. This suggests that the aluminate end-group coordinates with the penultimate ester group of the polymer chain, thus decreasing reactivity. The results are at variance with an activated monomer mechanism.
Rayleigh-konstanten reiner lösungsmittel und ihre wellenlängenabhängigkeit
1956
Die Rayleigh-Konstanten von Benzol und Toluol bei 366, 405, 436, 546 und 578 mμ und von Schwefelkohlenstoff bei 436, 546 und 578 mμ werden bestimmt. Die Berechnung der absoluten Streuwerte dieser Losungsmittel wird under Anwendung der Rayleighschen Gleichung durchgefuhrt, indem die Streuung des Standard-Losungsmittels mit der einer Polymethylmethacrylat-Fraktion (Mw = 62 500) mit bekannten optischen Konstanten und bekanntem Mw verglichen wird. Dabei werden die Brechungskorrekturen berucksichtigt. Aus den fur die verschiedenen Losungsmittel bei den einzelnen Wellenlangen ermittelten Rayleigh-Konstanten wird nach der Einstein-Smoluchowskischen Schwankungs-theorie der Lichtzerstreuung die Losc…
Gamma radiation induced polymerization of vinyl monomers in dense CO2
2002
Abstract The dispersion polymerization of methyl methacrylate in dense carbon dioxide, initiated by γ-rays, utilizing different polysiloxanes as polymeric stabilizers, was investigated. The progress of the reaction, as a function of the irradiation dose, was also studied and the occurrence of a gel effect has been detected. For comparison, the dispersion polymerization has been carried out in supercritical conditions ( T =65°C and 38 MPa) in the presence of 2,2′-azobis(isobutyronitrile) (AIBN) as initiator. High molecular weight polymer (M w > 1000 kg/mol) with narrow molecular weight distribution has been obtained both with γ-rays and AIBN. The electron scanning micrographs show that regul…