Search results for "Hexane"
showing 10 items of 467 documents
A new experimental protocol for intrazeolite photooxidations. The first product-based estimate of an upper limit for the intrazeolite singlet oxygen …
2002
The intrazeolite photooxidations of several alkenes have been examined in hexane and in perfluorohexane slurries. The ability of perfluorohexane to increase the affinity of alkenes for the interior of the zeolite was documented. The nearly identical reaction rates in the two slurry solvents are attributed to a leveling of the singlet oxygen lifetime by the zeolite framework. A consideration of the rates of the various intrazeolite processes was used to estimate an upper limit for the intrazeolite lifetime of singlet oxygen.
Interfacial tension of demixed polymer solutions: augmentation by polymer additives
1997
The interfacial tension between phase separated polymer solutions increases pronouncedly upon the addition of asmall amounts of incompatible polymers. This feature is demonstrated by means of measurements with solutions of polystyrene in cyclohexane and the folloowing additives: poly(styrene-block-dimethylsiloxane), polyisobutylene and polydimethylsiloxane. Theoretical considerations based on a correlation between the lenth of the tie lines and the corresponding interfacial tension corroborates this finding
Branched versus linear polyisoprene: Fractionation and phase behavior
2007
Abstract Branched polyisoprene (PI) was prepared from PI-macromonomers. Linear byproducts of the synthesized polymer were removed by means of inverse spin fractionation, using the solvent cyclohexane (CH) and the precipitant acetone (AC). A well-defined fraction (Mw = 17.5 kg/mol, Mw/Mn = 1.8) of the branched polyisoprene obtained in this manner was used to determine different phase diagrams with branched and/or linear PI in the mixed solvent CH/AC at 25 °C. For comparable molar masses of the polymers the two-phase area is smallest for the branched PI and slightly larger for the linear PI; in the case of the unfractionated original sample of the branched polymer one observes a pronounced pe…
Improvement of biphasic polymerization by application of binary ionic liquid mixture
2013
Abstract The mixture of two ionic liquids, 1- n -butyl-3-methylimidazolium and 1-(2-phenylethyl)-3-methylimidazolium chloroaluminates, [C 4 -mim][AlCl 4 ] and [PhC 2 -mim][AlCl 4 ], were applied as a medium to immobilize the Cp 2 TiCl 2 titanocene catalyst for biphasic ionic liquid/hexane ethylene polymerization. The system makes possible to perform the reaction at lower temperatures, below the melting temperature of the aralkyl ionic liquid. A better separation of the ionic liquid phase was observed and an easier mass transfer of the polymer product from the ionic liquid to the hexane phase was obtained. The polyethylene reveals bimodal distribution of molecular weight. It is characterized…
Über die möglichkeit der bildung makrocyclischer polyoxyniethylene. 29. mitt über polyoxymethylene1
1966
Bei der kationischen Polymerisation von 1,3,5-Trioxan in Cyclohexan entstehen Polyoxymethylene, welche partiell thermisch stabil und alkalibestandig sind, ohne das irgendwelche bekamiten stabilen Endgruppen nachgewiesen werden konnten. Moglicberweise handelt es sich hierbei um Makrocyclen. Cationic polymerization of 1,3,5-trioxan in cyclohexane yields polyoxymethylene which is partially stable to heat and to alkali but does not contain any of the known stable endgroups. These polymers possibly have a macrocyclic structure.
Crystal structure of 1-hydroxy-2,2,6,6-tetramethylpiperidin-1-ium trifluoromethanesulfonate
2015
In the cation of the title salt, C9H20NO+·CF3O3S−, the six-membered heterocyclic ring displays a chair conformation. In the crystal, centrosymmetric pairs of cations and anions are linked by N—H...O and O—H...O hydrogen bonds to form rings with aR44(14) graph-set motif.
Densities and viscosities of imidazolium and pyridinium chloroaluminate ionic liquids
2013
Abstract The chloroaluminate ionic liquids are used in various types of reactions. However, due to their particular vulnerability on water, their physical properties have not been previously investigated very extensively. The densities and viscosities of series imidazolium and pyridinium chloroaluminate ionic liquids having alkyl (butyl, hexyl, octyl) or aralkyl (benzyl, ethylphenyl) chain at the cation, various effective molar fraction of AlCl 3 (χ AlCl3 = 0.5, 0.65, 0.7), as well as they mixture and mixture with common organic solvents (hexane, toluene) were measured at the temperature range 293.15–343.15 K (20–70 °C). Densities, and particularly viscosities decrease with the increase of…
Structural Investigation of Water/Lecithin/Cyclohexane Microemulsions by FT-IR Spectroscopy
1995
Abstract FT-IR spectra of water/lecithin/deuterated cyclohexane microemulsions as a function of water/lecithin molar ratio R ( R = [water]/[lecithin]) at various volume fractions ( O ) of the micellar phase have been recorded at 25°C. After elimination of the small spectral contributions due to deuterated cyclohexane and normalization, the shape of the C–H stretching band due to lecithin has been found dependent upon R and O whereas that of the O–H stretching band has been found dependent only upon R . The change in shape of the C–H band was interpreted in terms of a modification of the lecithin alkyl chain packing order. The analysis of the O–H band provides evidence that the hydroxylic gr…
Über die polymeranaloge bromierung von naturkautschuk und einige lösungseigensch aften des bromkautschuks. Über die molekularen konstanten von naturk…
1961
Naturkautschuk last sich in verdunnter Losung in Cyclohexan bromieren, wobei das Molekulargewicht entsprechend dem Bromgehalt zunimmt (polymeranaloge Umsetzung). Fur Bromkautschuk steigenden Bromgehalts wird Cyclohexan ein zunehmend schlechteres Losungsmittel, was sich in einer Abnahme des 2. osmotischen Virialkoeffizienten und einer Kontraktion des Molekulknauels zeigt. Dieses Ergebnis wird in quantitativer Ubereinstimmung durch Viskositats- und Lichtstreuungsmessungen erhalten. Cyclohexanlosungen von Bromkautschuk mit 43% Brom haben bei Zimmertemperatur einen Θ-Punkt. In diesem Zustand ist der Knauel 1,74mal groser als bei freier Drehbarkeit, in ziemlich guter Ubereinstimmung mit dem an a…
Effect of S1 Torsional Dynamics on the Time-Resolved Fluorescence Spectra of 9,9‘-Bianthryl in Solution
1997
Time-resolved fluorescence spectra of 9,9‘-bianthryl (BA) were measured in methylcyclohexane (MCH) and a Decalin−isooctane (D−ISOO) mixture at several temperatures between 127 and 200 K. A suitable...