Search results for "polymerization"
showing 10 items of 1689 documents
ChemInform Abstract: Cycloaddition Reactions with Vinyl Heterocycles
2010
Publisher Summary The Diels-Alder reaction is one of the most common and elegant methods for the construction of six-membered rings. Although the number of Diels-Alder cycloadditions with open-chain and alicyclic dienes is very large, the number of examples with aromatic heterocyclic compounds is relatively small. The introduction of a vinyl group as a substituent onto a heterocycle increases the number of possible reactions. This new possibility, however attractive for synthetic purposes, is successful only with π-excessive five-membered heterocyclic derivatives with a few exceptions. The chapter discusses the reactions of vinyl heterocycles with carbodienophiles. The endocyclic and exo-en…
A continuous reaction system to investigate dispersion polymerization of vinyl monomers in supercritical carbon dioxide
2006
A laboratory-scale continuous reaction system using a stirred tank reac- tor was assembled in our laboratory to study the dispersion polymerization of vinyl monomers in supercritical carbon dioxide (scCO2). The apparatus was equipped with a suitable downstream separation section to collect solid particles entrained in the effluent stream from the reactor, whose monomer concentration could be measured online with a gas chromatograph. The dispersion polymerization of methyl methacry- late in scCO2 was selected as a model process to be investigated in the apparatus. The experiments were performed at 65 8C and 25 MPa with 2,2 0 -azobisisobutyroni- trile as the initiator and a reactive polysilox…
Polymerization of vinylidene fluoride with perfluoropolyether surfactants in supercritical carbon dioxide as a dispersing medium
2006
The heterogeneous polymerization of vinylidene fluoride (VDF) was investigated at 50 °C with supercritical carbon dioxide (scCO 2 ) as a dispersing medium and diethylperoxidicarbonate as an initiator in the presence of different perfluoropolyether surfactants. When FLK 7004A ammonium carboxylate salts were used at a 5% (w/w) concentration with respect to VDF, with an initial pressure of 31-45 MPa and with an olefin concentration of about 5.5 mol/L, monomer conversions up to 63% were obtained, corresponding to a final solid content higher than 200 g/L, and the polymer was collected at the end of the process in the form of a white powder completely composed of microspheres. The effects of the…
Imidazolium functionalized carbon nanotubes for the synthesis of cyclic carbonates: reducing the gap between homogeneous and heterogeneous catalysis
2016
Single walled carbon nanotubes (SWCNTs) were functionalized with imidazolium salts bearing vinyl functionalities. An extremely high loading of active species was achieved through a straightforward one-pot procedure involving self-assembly of the imidazolium moieties followed by radical initiated polymerization of the double bonds. The materials were extensively characterized by transmission electron microscopy, Raman spectroscopy, nitrogen physisorption and combustion chemical analysis. The imidazolium functionalized SWCNTs displayed excellent catalytic activity for the reaction of CO2 and epoxides to produce cyclic carbonates as demonstrated by the excellent turnover numbers (TON). Moreove…
In situ UV-visible spectroelectrochemistry in the course of oxidative monomer electrolysis
2015
Abstract Novel method to characterize the macromolecuar structure of an electroactive polymer deposited via electrooxidation of the corresponding monomer on the electrode surface has been proposed. It is based on experimental determination of the number of electrons spent for oxidation of an initially solute monomer species which is used to calculate the number of covalent bonds linking each monomer unit with neighboring units inside the polymer. The former parameter is found by tracing simultaneously the variations of instantaneous values of the solute monomer concentration and of the passed charge in the course of the monomer oxidation electrolysis. This monomer concentration is establish…
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…
Aminoendgruppenhaltige polymere durch anionische polymerisation von vinylverbindungen mit 3-Dimethylaminopropyllithium als initiator
1975
α-Methylstyrol (in THF) sowie Styrol bzw. Butadien (in Benzol) wurden mit 3-Dimethyl-aminopropyllithium (1) als Initiator homopolymerisiert; dabei wurden aufgrund des Einflusses der tertiaren Aminogruppe bei der Polymerisation in apolarem Medium, verglichen mit der Initiierung durch Butyllithium, Veranderungen der Mikrostruktur der Polymeren beodachtet. Die Molekulargewichte der Polymeren sind hoher, als sich nach dem eingesetzten Monomer/Initiator-Verhatnis berechnete. Der Aminoendgruppengehalt der Polymeren wurde elementaranalytisch sowie NMR-spektroskopisch quantitative bestimmt; die tertiaren Aminoendgruppen konnten mit Methylijodid quantitativ zum quartaren Salz umgesetz werden, mit Br…
Organocatalytic synthesis of new telechelic polycarbonates and study of their chemical reactivity
2015
Abstract A two-step versatile process for telechelic polycarbonates synthesis is described. 1-n-butyl-3-methylimidazolium-2-carboxylate (BMIM-2-CO2) was used as thermolabile precursor of N-heterocyclic carbene (NHC) organocatalyst. In a first step, synthesized branched fatty diols or commercially available linear diols were reacted with an excess of dimethylcarbonate (DMC) to afford oligocarbonates with methylcarbonate end-groups. Then, the methylcarbonate groups were reacted with hydroxyl groups of 9-decen-1-ol, 4-hexyn-1-ol and 4-hydroxybenzene ethanol leading to telechelic oligomers with alkene, alkyne and phenol functionalities. Reactivity of these end-groups towards polymerization was …
Efficiency Boosting of Surfactants with Poly(ethylene oxide)-Poly(alkyl glycidyl ether)s: A New Class of Amphiphilic Polymers
2020
Twenty years ago, it was found that adding small amounts of amphiphilic block copolymers like poly(ethylene propylene)-co-poly(ethylene oxide) (PEP-b-PEO) to microemulsion systems strongly increases the efficiency of medium-chain surfactants to solubilize water and oil. Although being predestined to serve as a milestone in microemulsion research, the effect has only scarcely found its way into applications. In this work, we propose new types of efficiency boosters, namely, poly(ethylene oxide)-poly(alkyl glycidyl ether carbonate)s (PEO-b-PAlkGE) and their "carbonated" poly(ethylene oxide)-poly(carbonate alkyl glycidyl ether) analogs. Their synthesis via anionic ring-opening polymerization (…
Synthesis and catalytic studies of Ti-anchored disilanol isobutyl-POSS/alkylaluminum system
2012
Abstract Titanium (IV) precursors anchored to alkyl substituted polyhedral oligomeric silsesquioxane (POSS) disilanol were prepared and characterized. These catalysts formulated as [Ti(O^O)2] and [M(O^O)XCl] are found to be active in polymerization of ethylene at high temperatures in combination with ethylaluminum sesquichloride (Et3Al2Cl3) as co-catalyst. The polyethylene product so obtained is linear, crystalline and displays narrow dispersities. The unique low molecular weight PE formed in this reaction exhibit properties that have potential industrial applications. The effect of various reaction parameters on catalyst performance is described.