Vana, Philipp

[["dc.bibliographiccitation.firstpage","1484"],["dc.bibliographiccitation.issue","11"],["dc.bibliographiccitation.journal","Australian Journal of Chemistry"],["dc.bibliographiccitation.lastpage","1487"],["dc.bibliographiccitation.volume","62"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Meiser, Wibke"],["dc.contributor.author","Vana, Philipp"],["dc.date.accessioned","2018-11-07T08:33:50Z"],["dc.date.available","2018-11-07T08:33:50Z"],["dc.date.issued","2009"],["dc.description.abstract","Reversible addition-fragmentation chain transfer (RAFT) polymerizations of methyl methacrylate (MMA) in bulk at 60 degrees C were performed at five pressures up to 200 MPa using 2-(2'-cyanopropyl)dithiobenzoate (CPDB) as RAFT agent at concentrations between 1.5 x 10(-3) and 2.0 x 10(-2) mol L(-1). Applying high pressure during polymerization increases the rate of polymerization, but no effect on polydispersity was observed. Molecular weight distributions and average molecular weights of the final polymer indicated the successful control of MMA polymerization even at low CPDB concentrations. The slight retardation observed is adequately described by the dependence the termination rate coefficient, k(t), on the chain-length."],["dc.identifier.doi","10.1071/CH09219"],["dc.identifier.isi","000271976400007"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/17683"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Csiro Publishing"],["dc.relation.issn","0004-9425"],["dc.title","Mechanism of CPDB-Mediated RAFT Polymerization of Methyl Methacrylate: Influence of Pressure and RAFT Agent Concentration"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","5590"],["dc.bibliographiccitation.issue","19"],["dc.bibliographiccitation.journal","Polymer"],["dc.bibliographiccitation.lastpage","5598"],["dc.bibliographiccitation.volume","48"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Frauendorf, Holm"],["dc.contributor.author","GUnzler, Fabian"],["dc.contributor.author","Vana, Philipp"],["dc.date.accessioned","2018-11-07T10:58:38Z"],["dc.date.available","2018-11-07T10:58:38Z"],["dc.date.issued","2007"],["dc.description.abstract","The type and number of end groups of poly(methyl methacrylates) from free-radical polymerization with six diacyl peroxides, R-(CO)O- O(CO)-R. acting as initiators have been analyzed via electrospray ionization mass spectrometry using an ion trap and additionally Fourier transform ion cyclotron resonance for mass detection. The polymerizations were carried out in benzene solution at high initiator concentration to yield low molecular weight polymer. With R being an alkyl group, only R moieties are observed as end groups. For each oligomer size, molecules with one or two such end groups are formed, depending on whether termination occurs via disproportionation or combination. With R being an aryl type, as in di-benzoyl and di-naphthoyl peroxides, both R and R-(CO)O moieties are detected as polymeric end groups. Because of aromatic delocalization. fractions of the arylic R-(CO)O-center dot radicals are sufficiently long living at 95 degrees C to add to a monomer molecule prior to undergo decarboxylation. (C) 2007 Elsevier Ltd. All rights reserved."],["dc.identifier.doi","10.1016/j.polymer.2007.07.041"],["dc.identifier.isi","000250161000018"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/50507"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Sci Ltd"],["dc.relation.issn","0032-3861"],["dc.title","Electrospray ionization mass spectrometric end-group analysis of PMMA produced by radical polymerization using diacyl peroxide initiators"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","779"],["dc.bibliographiccitation.issue","10"],["dc.bibliographiccitation.journal","Australian Journal of Chemistry"],["dc.bibliographiccitation.lastpage","787"],["dc.bibliographiccitation.volume","60"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Hesse, Pascal"],["dc.contributor.author","Junkers, Thomas"],["dc.contributor.author","Theis, Thomas"],["dc.contributor.author","Vana, Philipp"],["dc.date.accessioned","2018-11-07T11:06:03Z"],["dc.date.available","2018-11-07T11:06:03Z"],["dc.date.issued","2007"],["dc.description.abstract","The chain-length dependence of the termination rate coefficient, k(t), in methyl acrylate ( MA) and dodecyl acrylate (DA) radical polymerization has been determined via the single pulse pulsed-laser polymerization near-infrared reversible addition-fragmentation chain transfer (SP-PLP-NIR-RAFT) technique. Polymerization is induced by a laser SP and the resulting decay in monomer concentration, c(M), is monitored via NIR spectroscopy with a time resolution of microseconds. A RAFT agent ensures the correlation of radical chain length and monomer-to-polymer conversion. The obtained rate coefficients for termination of two radicals of approximately the same chain length, i, are represented by power-law expressions, k(t)(i, i)alpha i(-alpha). For both monomers, composite model behaviour of k(t)(i, i) showing two distinct chain length regimes is observed. The exponent as referring to short chain lengths is close to unity, whereas the exponent alpha(1), which characterizes the chain-length dependency of large radicals, is slightly above the theoretical value for coiled chain-end radicals. The crossover chain length, i(c), which separates the two regions, decreases from MA(i(c) = 30) to DA(i(c) = 20). The results for MA and DA are consistent with earlier data reported for butyl acrylate. There appears to be a correlation of as and ic with chain flexibility."],["dc.identifier.doi","10.1071/CH07236"],["dc.identifier.isi","000250003800010"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/52214"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Csiro Publishing"],["dc.publisher.place","Clayton"],["dc.relation.conference","29th Australasian Polymer Symposium"],["dc.relation.eventlocation","Hobart, AUSTRALIA"],["dc.relation.issn","1445-0038"],["dc.relation.issn","0004-9425"],["dc.title","Chain-length-dependent termination in acrylate radical polymerization studied via pulsed-laser-initiated RAFT polymerization"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1299"],["dc.bibliographiccitation.issue","16"],["dc.bibliographiccitation.journal","Macromolecular Rapid Communications"],["dc.bibliographiccitation.lastpage","1305"],["dc.bibliographiccitation.volume","27"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Vana, Philipp"],["dc.date.accessioned","2018-11-07T09:25:01Z"],["dc.date.available","2018-11-07T09:25:01Z"],["dc.date.issued","2006"],["dc.description.abstract","The debate on the mechanism of dithiobenzoate-mediated RAFT polymerization may be resolved by including the reaction between a propagating radical and the star-shaped combination product from irreversible termination into the kinetic scheme. By this step, a highly reactive propagating radical and a not overly stable three-arm star species are transformed into the resonance-stabilized RAFT intermediate radical and a very stable polymer molecule. The time evolution of concentration is discussed for the main-equilibrium range of CDB-mediated methyl acrylate polymerization."],["dc.identifier.doi","10.1002/marc.200600317"],["dc.identifier.isi","000240426600001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/29969"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-blackwell"],["dc.relation.issn","1022-1336"],["dc.title","Mechanism of dithiobenzoate-mediated RAFT polymerization: A missing reaction step"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","6071"],["dc.bibliographiccitation.issue","18"],["dc.bibliographiccitation.journal","Journal of Polymer Science Part A Polymer Chemistry"],["dc.bibliographiccitation.lastpage","6081"],["dc.bibliographiccitation.volume","46"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Frauendorf, Holm"],["dc.contributor.author","Janssen, Olaf"],["dc.contributor.author","Vana, Philipp"],["dc.date.accessioned","2018-11-07T11:10:57Z"],["dc.date.available","2018-11-07T11:10:57Z"],["dc.date.issued","2008"],["dc.description.abstract","Initiation by diethyl peroxydicarbonate (E-PDC), di-n-tetradecyl peroxydicarbonate (nTD-PDC), di-n-hexadecyl peroxydicarbonate (nHD-PDC), and di-2-ethylhexyl peroxydicarbonate (2EH-PDC) of free-radical polymerizations of methyl methacrylate in benzene solution was studied by end-group analysis via electrospray ionization mass spectrometry (ESI-MS). Unambiguous assignment of ESI-MS peaks allows for identification of the type of radical that starts chain growth. In case of initiation by dialkyl peroxydicarbonates with linear alkyl groups, almost exclusively alkoxy carbonyloxyl species, which are the primary fragments from initiator decomposition, occur as end-groups. With 2EH-PDC, however, both the primary 2-ethylhexoxy carbonyloxyl fragment and a second moiety, which is formed by decarboxylation of the 2-ethylhexoxy carbonyloxyl radical, are clearly observed as end-groups. The decarboxylation process is described by a concerted mechanism which involves a 1,5-hydrogen shift reaction. (C) 2008 Wiley Periodicals, Inc."],["dc.description.sponsorship","Deutsche Forschungsgemeinschaft [Bu 426/10-1]"],["dc.identifier.doi","10.1002/pola.22919"],["dc.identifier.isi","000259325100011"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/53320"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","John Wiley & Sons Inc"],["dc.relation.issn","0887-624X"],["dc.title","Electrospray ionization mass spectrometric study of end-groups in peroxydicarbonate-initiated radical polymerization"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1900345"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Macromolecular Chemistry and Physics"],["dc.bibliographiccitation.volume","221"],["dc.contributor.author","Nitschke, Annika"],["dc.contributor.author","Riemann, Lara"],["dc.contributor.author","Kollenbach, Leon"],["dc.contributor.author","Braun, Vanessa"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Vana, Philipp"],["dc.date.accessioned","2020-12-10T14:06:54Z"],["dc.date.available","2020-12-10T14:06:54Z"],["dc.date.issued","2019"],["dc.identifier.doi","10.1002/macp.201900345"],["dc.identifier.eissn","1521-3935"],["dc.identifier.issn","1022-1352"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/70069"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.relation.eissn","1521-3935"],["dc.relation.issn","1022-1352"],["dc.title","Investigation into the Kinetics of n ‐Pentyl Methacrylate Radical Polymerization"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","5977"],["dc.bibliographiccitation.issue","25"],["dc.bibliographiccitation.journal","Polymer"],["dc.bibliographiccitation.lastpage","5982"],["dc.bibliographiccitation.volume","51"],["dc.contributor.author","Meiser, Wibke"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Barth, Johannes"],["dc.contributor.author","Vana, Philipp"],["dc.date.accessioned","2018-11-07T08:36:38Z"],["dc.date.available","2018-11-07T08:36:38Z"],["dc.date.issued","2010"],["dc.description.abstract","Addition and fragmentation rate coefficients, k(ad) and k(beta), have been measured by individually tracing intermediate and propagating radical concentrations via highly time-resolved EPR spectroscopy after applying a laser single pulse. The method is illustrated for butyl acrylate polymerization at -40 degrees C with EDTCP (ethyl 2[1-diethoxyphosphoryl-2,2,2-trifluoroethoxythio carbonylsulfanyl] propionate) being the MADIX agent Analysis of the radical concentration vs. time profiles yields k(ad) = (2.5 +/- 0.1) x 10(4) L mol(-1) s(-1) and k(beta) = (2.3 +/- 0.3) x 10(3) s(-1). The associated K(eq) = k(ad)/k(beta) value is in close agreement with K(eq) deduced from an earlier EPR method which rests on measuring the ratio of intermediate and propagating radical concentrations during stationary polymerization. (C) 2010 Elsevier Ltd. All rights reserved."],["dc.description.sponsorship","Fonds der Chemischen Industrie"],["dc.identifier.doi","10.1016/j.polymer.2010.10.019"],["dc.identifier.isi","000284793500012"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/18365"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Sci Ltd"],["dc.relation.issn","0032-3861"],["dc.title","RAFT/MADIX rate coefficients measured via time-resolved EPR spectroscopy after pulse laser initiation"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","2474"],["dc.bibliographiccitation.issue","8"],["dc.bibliographiccitation.journal","Macromolecules"],["dc.bibliographiccitation.lastpage","2480"],["dc.bibliographiccitation.volume","44"],["dc.contributor.author","Meiser, Wibke"],["dc.contributor.author","Barth, Johannes"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Kattner, Hendrik"],["dc.contributor.author","Vana, Philipp"],["dc.date.accessioned","2018-11-07T08:56:56Z"],["dc.date.available","2018-11-07T08:56:56Z"],["dc.date.issued","2011"],["dc.description.abstract","The kinetics of reversible addition fragmentation chain transfer (RAFT) polymerization of butyl acrylate with ethyl S-thiobenzoyl-2-thiopropionate (ETTP) as the RAFT agent has been studied. The concentrations of propagating (P-center dot) and intermediate radicals (INT\") were measured via highly time-resolved EPR spectroscopy after initiation by a laser single pulse. Predici simulation of experimental data results in rate coefficients for -40 degrees C of k(ad) = (1.4 +/- 0 4) x 10(6)L mol(-1) s(-1), k(beta) = (4.7 +/- 1.5) s(-1), and k(t)(cross) = 0.25 x k(upsilon), where k(t) is the rate coefficient for termination of two P-center dot species. Fast fragmentation of the intermediate radical is thus observed at this low temperature. Measuring the ratio of INT center dot to P-center dot concentrations during stationary polymerization at -40 and -70 degrees C yields K-eq = k(ad)/k(beta) values of (2.3 +/- 0.6) x 10(5) and 75 +/- 15 L mol(-1), respectively, which correspond to an apparent activation energy difference, E-A(k(ad)/k(beta)), of -49.5 kJ mol(-1)."],["dc.description.sponsorship","Fonds der Chemischen Industrie"],["dc.identifier.doi","10.1021/ma102491x"],["dc.identifier.isi","000289593200013"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9445"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/23267"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","0024-9297"],["dc.rights","Goescholar"],["dc.rights.uri","https://goescholar.uni-goettingen.de/licenses"],["dc.title","EPR Measurement of Fragmentation Kinetics in Dithiobenzoate-Mediated RAFT Polymerization"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","652"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Macromolecules"],["dc.bibliographiccitation.lastpage","662"],["dc.bibliographiccitation.volume","42"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Guenzler, Fabian"],["dc.contributor.author","Russell, Gregory T."],["dc.contributor.author","Vana, Philipp"],["dc.date.accessioned","2018-11-07T08:32:46Z"],["dc.date.available","2018-11-07T08:32:46Z"],["dc.date.issued","2009"],["dc.description.abstract","We comprehensively explore the use of mass spectrometry (MS) for quantitative determination of the mode of termination, i.e., the extent of disproportionation versus combination, in radical polymerization. Development of the underlying kinetic theory forms a major portion of our endeavors. What emerges from this theory is that the ratio of polymer from disproportionation to combination is a function of chain length and of fundamental kinetic parameters such as the rate of initiation and the rate coefficients for propagation and termination. Therefore, all this information must be at hand in order to determine lambda, the fraction of termination by disproportionation. We implement our findings using electrospray-ionization MS results for poly(methyl methacrylate) that we synthesized at 85 degrees C in benzene employing bis(3,5,5-trimethylhexanoyl) peroxide as initiator, chosen because it has the advantage of yielding only one primary radical species. Our results are well fitted by theory and are found to vary with chain length and initiator concentration as predicted. We also address the issue that signal intensities from macromolecular MS techniques may not give the true molecular weight distribution of a sample because of variation of ionization efficiency with species mass. We devise a way of obtaining lambda from data for hypothetical combination and disproportionation species of identical mass. Our final result is lambda = 0.63 +/- 0.10, suggesting that disproportionation is not as rampant in methyl methacrylate systems as commonly thought."],["dc.description.sponsorship","Deutsche Forschungsgemeinschaft [BU 426/10]"],["dc.identifier.doi","10.1021/ma801732r"],["dc.identifier.isi","000263035100014"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/17418"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","0024-9297"],["dc.title","Determination of the Mode of Termination in Radical Polymerization via Mass Spectrometry"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1591"],["dc.bibliographiccitation.issue","19"],["dc.bibliographiccitation.journal","Macromolecular Chemistry and Physics"],["dc.bibliographiccitation.lastpage","1599"],["dc.bibliographiccitation.volume","210"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Frauendorf, Holm"],["dc.contributor.author","Guenzler, Fabian"],["dc.contributor.author","Huff, Felix"],["dc.contributor.author","Vana, Philipp"],["dc.date.accessioned","2018-11-07T11:23:14Z"],["dc.date.available","2018-11-07T11:23:14Z"],["dc.date.issued","2009"],["dc.description.abstract","A method for measuring initiator efficiency in radical polymerization using ESI-MS is presented. The method is based on the evaluation of relative MS peak intensities of polymer that has been initiated by a mixture of initiators, of which one serves as an internal reference. The method is quickly and easily performed and was found to be reproducible and robust. In polymerization of methyl methacrylate in solution, the efficiency of BTMHP at 80 degrees C was determined to be f(BTMHP) =0.57 +/- 0.08, and the efficiency of DBPO at 100 degrees C was measured to be f(DBPO) = 0-89 +/- 0.08."],["dc.description.sponsorship","Deutsche Forschungsgemeinschaft [Bu 426/10-2]"],["dc.identifier.doi","10.1002/macp.200900237"],["dc.identifier.isi","000270859800003"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/56155"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-v C H Verlag Gmbh"],["dc.relation.issn","1022-1352"],["dc.title","Determining Initiator Efficiency in Radical Polymerization by Electrospray-Ionization Mass Spectrometry"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]