Search results for "ionic"
showing 10 items of 2016 documents
Does short-term potassium fertilization improve recovery from drought stress in laurel?
2014
Xylem hydraulic conductance varies in response to changes in sap solute content, and in particular of potassium (K(+)) ion concentration. This phenomenon, known as the 'ionic effect', is enhanced in embolized stems, where it can compensate for cavitation-induced loss of hydraulic conductance. Previous studies have shown that in well-watered laurel plants (Laurus nobilis L.), potassium concentration of the xylem sap and plant hydraulic conductance increased 24 h after fertilization with KCl. The aim of this work was to test whether water-stressed laurel plants, grown under low potassium availability, could recover earlier from stress when irrigated with a KCl solution instead of potassium-fr…
Thermophysical properties of binary mixtures of 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ionic liquid with alcohols at several tempera…
2018
Abstract Densities, speeds of sound, and refractive indices for the binary systems made up by 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate and methanol, ethanol, 1-propanol, or 2-propanol, as well as for the pure components, have been measured covering the whole range of compositions at atmospheric pressure and T = (278.15–338.15) K. From densities and speeds of sound, isentropic compressibilities were calculated using the Newton-Laplace equation. Liquid ideal-mixture properties have been defined and calculated, and they have been used to determine excess molar volumes, excess isentropic compressibilities, and deviations in refractive indices. Excess and deviations in properties …
Volumetric and Ultrasonic Studies of 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate Ionic Liquid with Methanol, Ethanol, 1-Propanol, and Water…
2007
The speed of sound and density of mixtures of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][triflate]) with methanol, ethanol, 1-propanol, and water, as well as of the pure components have been experimentally measured over the whole range of compositions at T = (278.15 to 338.15) K and atmospheric pressure. From these experimental data, the excess molar volume, excess isentropic compressibility, and excess speed of sound have been calculated and fitted to an extended version of the Redlich−Kister equation, which takes into account the dependence on composition and temperature simultaneously. The Prigogine−Flory−Patterson theory has also been used to explain the behavior of t…
Synthesis of Linear and Star-Shaped Block Copolymers of Isobutylene and Methacrylates by Combination of Living Cationic and Anionic Polymerizations
1998
A new synthetic route for the preparation of polyisobutylene (PIB)-based linear and star-shaped block copolymers was developed by combining living carbocationic and anionic polymerizations. Living PIB chains were quantitatively endcapped with 1,1-diphenylethylene, leading to 1,1-diphenyl-1-methoxy (DPOMe) or 2,2-diphenylvinyl (DPV) termini, or both. Both the DPOMe- and DPV-terminated PIBs, and the mixtures of both endgroups were quantitatively metalated with K/Na alloy, Cs metal, or Li dispersion in THF at room temperature. The resulting stable macrocarbanion obtained by metalation with K/Na alloy was used to initiate living anionic polymerization of tert-butyl methacrylate (tBMA) yielding …
Synthesis of linear and three-arm star tert-chlorine-telechelic polyisobutylenes by a two-step conventional laboratory process
1997
A two-step conventional laboratory process was developed for the synthesis of mono- and difunctional linear and three-arm star tert-chlorine-telechelic polyisobutylenes (PIB) with desired molecular weights (MW) and narrow molecular weight distribution (MWD) by living carbocationic polymerization (LCCP). This polymerization method applies easy to handle operations and chemicals. LCCP of isobutylene (IB), was carried out in CH2Cl2 as solvent and with BCl3 as coinitiator in the first step to obtain soluble low MW PIB prepolymer with narrow MWD. This was followed by addition of hexane, TiCl4 and additional monomer in the second step to prepare PIBs with desired MW and narrow MWD in practically …
Endfunctional Polymers by Functionalization of Living Cationic Chain Ends with 1,1-Diphenylethylene
1995
Abstract A new functionalization method has been developed for the synthesis of 2,2-diphenylvinyl(DPV)-telechelic polyisobutylene (PIB). First, living carbocationic polymerization (LCCP) of isobutylene (IB) is quantitatively end-quenched with a nonpolymerizable olefin, 1,1-diphenylethylene (DPE). This process yields a mixture of diphenyl substituted vinyl and tertiary chlorine endgroups. Treatment of the resulting polymer with potassium-tert-butoxide (tBuOK) leads to the quantitative formation of DPV-telechelic PIB which is a potential macroinitiator precursor for living anionic polymerizations.
Non-ionic photo-acid generators for applications in two-photon lithography
2009
Non-ionic photoacid generators (PAGs) have been designed and synthesized for use in two-photon lithography (TPL). The chromophores in these new PAGs are covalently linked to the photocleavable group by a flexible joint. Their thermal stability, solubility and efficiency to produce acid under both one- and two-photon excitation were characterized. The potential of these PAGs for TPL was tested in two negative-tone resist systems relying on different mechanisms: free-radical/cationic polymerization or a cationically initiated cross-linking reaction. These PAGs needed lower threshold power for polymerization compared to a commercially available photoinitiator, isopropylthioxanthone, and a phot…
Meinvalda pārgrupēšanās jonu šķidrumu vidē
2016
Meinvalda pārgrupēšanās jonu šķidrumu vidē. Ikkere L.E., darba vadītājs Dr.h.ķīm., prof. Zicmanis A. Bakalaura darbs, 54 lappuses, 24 attēli, 12 tabulas, 42 literatūras avoti, 5 pielikumi. Latviešu valodā. Bakalaura darba literatūras apskatā ir apkopota galvenā informācija par Meinvalda pārgrupēšanās reakcijām, to katalizatoriem, kā arī par jonu šķidrumiem. Laboratorijā tika veikta trīs jonu šķidrumu sintēze. To struktūras tika pierādītas, izmantojot 1H KMR un IS spektroskopijas metodes. Tika piemeklēti piemērotākie gāzu hromatogrāfijas apstākļi, lai noteiktu pārgrupēšanās reakciju izejvielas un produktus. Tika pārbaudīti dažādu anjonu un slāpekli saturošu katjonu jonu šķidrumu izmantošana …
Knēvenāgela kondensācijas kinētika jonu šķidrumos
2015
Knēvenāgela kondensācijas kinētika jonu šķidrumos. Ūdris N., zinātniskā vadītāja Mag. ķīm. Priede E. Kursa darbs 20 lappuses, 6 attēli, 5 tabulas, 12 literatūras avoti. Latviešu valodā. Darbā veikta četru jonu šķidrumu sintēze un attīrīšana, izmantojot dažādas metodes. Visiem sintezētajiem jonu šķidrumiem tika veikti Knēvenāgela kondensācijas kinētikas pētījumi, izmantojot jonu šķidrumu kā reakcijas vidi. Visiem jonu šķidrumam tika noteikta reakcijas ātruma konstante.
Skābekļa atomu saturošie imidazolija sāļi kondensācijas reakcijās
2021
Skābekļa atomu saturošie imidazolija sāļi kondensācijas reakcijās. Gradovska L., darba vadītāji Dr.h.ķīm., prof. Zicmanis A., Dr.chem. Baķis E. Maģistra darbs, 59 lappuses, 31 attēls, 5 tabulas, 43 literatūras avoti, 1 pielikums. Latviešu valodā. Literatūras apskatā apkopota informācija par biežāk aprakstītajiem jonu šķidrumiem un polietilēnglikola funkcionalizētajem jonu šķidrumiem, to iegūšanu un izmantošanas iespējām organiskajā katalīzē. Eksperimentālajā daļā sintezēti polietilēnglikola, spirtu un alkilvirkņu funkcionalizētie imidazolija rindas jonu šķidrumi, kuri izmantoti kā katalizatori un reakcijas vide Knēvenāgela kondensācijā. Reakcijas konversija atkarībā no laika novērtēta, izma…