Search results for "Anionic addition polymerization"

Controlling the Polymer Microstructure in Anionic Polymerization by Compartmentalization.

2018

An ideal random anionic copolymerization is forced to produce gradient structures by physical separation of two monomers in emulsion compartments. One monomer (M) is preferably soluble in the droplets, while the other one (D) prefers the continuous phase of a DMSO-in-cyclohexane emulsion. The living anionic copolymerization of two activated aziridines is thus confined to the DMSO compartments as polymerization occurs selectively in the droplets. Dilution of the continuous phase adjusts the local concentration of monomer D in the droplets and thus the gradient of the resulting copolymer. The copolymerizations in emulsion are monitored by real-time 1 H NMR kinetics, proving a change of the re…

Blockcopolymere aus 2-Isopropenylnaphthalin und Hexamethylcyclotrisiloxan, 7

1985

Anionic polymerization of 2-isopropenylnaphthalene (2-IPN), with butyllithium in THF at −78°C was terminated with ethylene oxide and the resulting terminal alkoxide was used to initiate the polymerization of hexamethylcyclotrisiloxane (D3) at +40°C. This led to the formation of AB-block copolymers which were coupled to ABBA-block copolymers by addition of dichlorodimethylsilane. ABBA-blockcopolymers were obtained with contents of polymethylsiloxane (poly(DMS)) between 77 and 84% of weight and block molecular weights between 1 700 and 27 000 (poly(2-IPN)) and 13 000 and 240 000 (poly(DMS)). Phase separation in polymer films casted from different solvents was studied by electron microscopy an…

Über den mechanismus der anionischen polymerisation von acrylnitril mit triphenylphosphin. 7. Mitt. über makrozwitterionen

1972

Die anionische Polymerisation von Acrylnitril mit Triathylphosphin als Initiator in Dimethylformamid wurde bei verschiedenen Temperaturen und unterschiedlichem Verhaltnis der Monomer/Initiator-Konzentrationen untersucht. Erganzt durch spektroskopische Endgruppenbestimmung der Polymeranionen konnte mittels 1H-NMR-Spektroskopie und Gelchromatographie (GPC) sowie emissionsspektralanalytischer Phosphorbestimmung an den rohen und den durch Umfallungen bzw. GPC fraktionierten Polymerproben gezeigt werden, das hier neben einer ubertragung teilweise eine Polymerisation Uber Makrozwitterionen auftritt. Fur die Bildung von Makrozwitterionen, , sind jedoch Mindestwerte des Monomer/Initiator-Verhaltnis…

1979

The kinetics of the anionic polymerization of styrene were investigated under pressure (1≤p/bar < 1800) with Na+ as counter ion in tetrahydropyran (THP) as solvent and with Cs+ as counter ion in 1,2-dimethoxyethane (DME) as solvent. The results yielded the activation volume of the contact ion pair ΔV and the sum (ΔV + ΔVcs) of the activation volume of the solvent separated ion pair ΔV and the volume change upon formation of solvent separated ion pairs from contact ion pairs ΔVcs. The numerical values are negative. The activation volume of the solvent separated ion pairs could be estimated.

Mechanism of anionic polymerization of methyl methacrylate in the presence of aluminium alkyls

1995

Methyl methacrylate was polymerized with tert-butyl lithium in the presence of triethylaluminium or triisobutylaluminium at 78°C in toluene. As indicated by GPC and MALDI-TOF mass spectrometry, the polymerization is accompanied by side reactions. The lower oligomers were fractionated by distillation and characterised by NMR, FT-IR, UV and electron impact (EI) mass spectrometry. All these data show that part of the polymer chains are carrying exactly one tert-butyl isoprenyl ketone unit. In order to avoid the formation of tert-butyl isoprenyl ketone a molar ratio of Al/Li>2 is necessary.

Influence of processing conditions on some properties of anionically synthesized polycaprolactam in presence of lithium chloride

1980

Nylon 6–LiCl systems of various concentrations were prepared by anionic polymerization of caprolactam in the presence of salt. A depression of both crystallization rate and melting temperature was evidenced through x-ray, density, and DSC analyses. Such a preliminary characterization allowed for choosing the proper conditions in order to obtain amorphous fibers from a spinning operation which was performed at a temperature lower than the pure polymer melting point. These results are of technological relevance, especially in view of obtaining, as in similar cases, large amorphous orientations through a spinning–drawing process and high-modulus fibers after subsequent crystallization. Also, t…

Hyperbranched-linear-hyperbranched ABA-type block copolymers based on poly(ethylene oxide) and polyglycerol

2009

BACKGROUND: Until recently, hyperbranched polymers were thought to be ill-defined materials that were not useful as building blocks for well-defined complex polymer architectures. It is a current challenge to develop strategies that offer rapid access to well-defined hyperbranched block copolymers. RESULTS: A convenient three-step protocol for the synthesis of double-hydrophilic hyperbranched–linear–hyperbranched ABA-type triblock copolymers based on poly(ethylene oxide) (PEO) and hyperbranched polyglycerol (hbPG) is presented. The Bola-type polymers exhibiting an aliphatic polyether structure were prepared from a linear (lin) linPG-b-PEO-b-linPG precursor triblock. The materials exhibit lo…

Effect of bulkiness and lewis acidity of aluminium compounds on the anionic polymerization of methyl methacrylate in toluene

1996

The bulkiness and the Lewis acidity of added aluminium compounds strongly affect the polymerization of methyl methacrylate in toluene at −78°C. The polymerization strongly deviates from ‘ideal’ first-order kinetics, i.e. the first-order time-conversion plots are kinked at low monomer conversions. Additionally, for the more bulky and more Lewis-acid aluminium alkyls, the time-conversion plots show a further downward curvature. This curvature is not the result of a termination reaction because the polymers are free of side products like β-ketoesters or vinyl ketone units. The molecular weight distributions and tacticities of the resulting polymers are also affected. Dependent on the aluminium…

Stimuli-Responsive Y-Shaped Polymer Brushes Based on Junction-Point-Reactive Block Copolymers

2012

Reversibly responsive, thin or ultrathin polymer fi lms, often referred to as “smart surfaces”, can alter their properties upon application of external stimuli. [ 1 , 2 ] One particular application fi eld represents the engineering of nanostructured fi lms mimicking cell membranes. [ 3 , 4 ] Such materials offer application potential for sensors, textiles, construction materials, and smart coatings due to a rapid change in surface energy and morphology. [ 5–7 ] The surface response can be triggered by various external stimuli such as light, temperature, electrical potential, mechanical force, magnetic fi eld, pH change, or selective solvent treatment. [ 1 , 8–12 ] A variety of different thi…

The effect of TMEDA on the kinetics of the anionic polymerization of methyl methacrylate in tetrahydrofuran using lithium as counterion

2000

The kinetics of the anionic polymerization of methyl methacrylate in presence of N,N,N', -tetramethylethylenediamine (TMEDA) in THF are investigated using 1,1-diphenyl-hexyllithium as initiator in a temperature range between -20°C and 0°C in a flow-tube reactor. The rate constants of propagation determined in the presence of TMEDA are compared to those obtained in the absence of a chelating agent. For propagation, the reaction order with respect to active centers is found to be 0.5 in both cases which indicates that the chelation of the lithium cation does not effectively perturb the aggregation of the enolate ion pair. Both the rate constants of propagation via non-aggregated ion pairs, k …