Vana, Philipp

[["dc.bibliographiccitation.firstpage","796"],["dc.bibliographiccitation.issue","10"],["dc.bibliographiccitation.journal","Macromolecular Rapid Communications"],["dc.bibliographiccitation.lastpage","802"],["dc.bibliographiccitation.volume","26"],["dc.contributor.author","Buback, M."],["dc.contributor.author","Junkers, T."],["dc.contributor.author","Vana, P."],["dc.date.accessioned","2018-11-07T11:00:23Z"],["dc.date.available","2018-11-07T11:00:23Z"],["dc.date.issued","2005"],["dc.description.abstract","A novel method combining RAFT polymerization with pulsed-laser initiation for determining chain-length dependent termination rate coefficients, k(t), is presented. Degenerative chain-transfer in RAFT enables single-pulse pulsed-laser polymerization (SP-PLP) traces to be measured on systems with a narrow radical distribution that remains essentially unchanged during the experiment. SP-PLP-RAFT experiments at different polymerization times allow for determining kt as a function of chain length via classical kinetics assuming chain-length independent k(t)."],["dc.identifier.doi","10.1002/marc.200500067"],["dc.identifier.isi","000229424200005"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/50904"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-v C H Verlag Gmbh"],["dc.relation.issn","1022-1336"],["dc.title","Laser single pulse initiated RAFT polymerization for assessing chain-length dependent radical termination kinetics"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","283"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Macromolecular Materials and Engineering"],["dc.bibliographiccitation.lastpage","293"],["dc.bibliographiccitation.volume","290"],["dc.contributor.author","Arita, T."],["dc.contributor.author","Beuermann, S."],["dc.contributor.author","Buback, M."],["dc.contributor.author","Vana, P."],["dc.date.accessioned","2018-11-07T11:07:46Z"],["dc.date.available","2018-11-07T11:07:46Z"],["dc.date.issued","2005"],["dc.description.abstract","Reversible addition fragmentation chain transfer (RAFT) polymerizations of methyl acrylate (MA) in solution containing either 22 vol.-% CO2 or toluene were performed at 80 ° C and 300 bar using cumyl dithiobenzoate (CDB) at concentrations between 1.8 x 10(-3) to 2.5 x 10(-2) mol (.) L-1 as the RAFT agent. Product molecular weight distributions and average molecular weights indicated the successful control of MA polymerization in CO2, even at low CDB concentrations. RAFT polymerization rates were strongly retarded by CDB and were in CO2 than in toluene solution. The enhanced fluidity associated with the addition of CO2 to the polymerizing system provided access to mechanistic details of RAFT polymerization. The data of the present study into MA, together with our recent results on RAFT polymerization of styrene in solution of CO2 and of toluene, suggest that self-termination of intermediate RAFT radicals is responsible for retardation in case of high concentrations of this intermediate and in case of enhanced fluidity, which may be achieved by polymerization in solution of CO2."],["dc.identifier.doi","10.1002/mame.200400274"],["dc.identifier.isi","000228888700008"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/52649"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-v C H Verlag Gmbh"],["dc.relation.issn","1438-7492"],["dc.title","RAFT polymerization of methyl acrylate in carbon dioxide"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","003"],["dc.bibliographiccitation.journal","e-Polymers"],["dc.contributor.author","Arita, T."],["dc.contributor.author","Beuermann, S."],["dc.contributor.author","Buback, M."],["dc.contributor.author","Vana, P."],["dc.date.accessioned","2018-11-07T10:51:48Z"],["dc.date.available","2018-11-07T10:51:48Z"],["dc.date.issued","2004"],["dc.description.abstract","Reversible addition fragmentation chain transfer (RAFT) polymerizations of styrene in fluid CO2 have been carried out at 80degreesC and 300 bar using cumyl dithiobenzoate as the controlling agent in the concentration range of 3.5.10(-3) to 2.1.10(-2) mol/L. This is the first report on RAFT polymerization in fluid CO2. The polymerization rates were retarded depending on the employed RAFT agent concentration with no significant difference between the RAFT polymerization performed in fluid CO2 and in toluene. Full chain length distributions were analyzed with respect to peak molecular weights, indicating the successful control of radical polymerization in fluid CO2. A characterization of the peak widths may suggest a minor influence of fluid CO2 on the addition reaction of macroradicals on the dithiobenzoate group."],["dc.identifier.isi","000188374100001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/48966"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","European Polymer Federation"],["dc.relation.issn","1618-7229"],["dc.title","Reversible addition fragmentation chain transfer (RAFT) polymerization of styrene in fluid CO2"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","605"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","Progress in Polymer Science"],["dc.bibliographiccitation.lastpage","643"],["dc.bibliographiccitation.volume","30"],["dc.contributor.author","Barner-Kowollik, C."],["dc.contributor.author","Buback, M."],["dc.contributor.author","Egorov, M."],["dc.contributor.author","Fukuda, T."],["dc.contributor.author","Goto, A."],["dc.contributor.author","Olaj, O. F."],["dc.contributor.author","Russell, Gregory T."],["dc.contributor.author","Vana, P."],["dc.contributor.author","Yamada, B."],["dc.contributor.author","Zetterlund, P. B."],["dc.date.accessioned","2018-11-07T10:58:33Z"],["dc.date.available","2018-11-07T10:58:33Z"],["dc.date.issued","2005"],["dc.description.abstract","The knowledge of accurate rate coefficients for individual steps of free-radical polymerization (FRP) is of scientific interest and of application-oriented importance. For a wide variety of homopolymerizations and for many copolymerizations, reliable propagation rate coefficients, k(P), are accessible via the IUPAC-reconiniended method of PLP-SEC (pulsed laser polymerization-size-exclusion chromatography). For termination rate coefficients, k(t). the situation is less favorable. Even for very common monomers, no k(t) benchmark data sets are available. Moreover, instead of having one recommended technique for measuring k(t). there are a plethora of such methods. Seventeen of the most prominent approaches for measuring k(t) are here reviewed, including innovative ones that have emerged over the last decade. The methods have been subdivided into two categories: (i) 'Kinetic methods', in which analysis of the time dependence of concentrations is essential, and (ii) 'MWD methods', in which the analysis of the molecular weight distribution plays the dominant role. The methods are evaluated with respect to their potential for providing routine access to measuring k(t) as a function of monomer conversion and of free-radical chain length. Moreover, it has been considered whether expensive instrumentation or highly demanding analysis is required for a particular method and whether a method is applicable to many types of monomers. A table summarizes all these evaluations in a readily accessible form. The use of kinetic methods appears to be generally preferable over MWD-based methods. The largest potential is currently seen for methods in which polymerization is induced by a single laser pulse and where the subsequent time evolution of either monomer concentration or free-radical concentration is measured. (c) 2005 Elsevier Ltd. All rights reserved."],["dc.identifier.doi","10.1016/j.progpolymsci.2005.02.001"],["dc.identifier.isi","000230253300001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/50493"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","0079-6700"],["dc.title","Critically evaluated termination rate coefficients for free-radical polymerization: Experimental methods"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","4266"],["dc.bibliographiccitation.issue","17"],["dc.bibliographiccitation.journal","Journal of Polymer Science Part A Polymer Chemistry"],["dc.bibliographiccitation.lastpage","4275"],["dc.bibliographiccitation.volume","42"],["dc.contributor.author","Buback, M."],["dc.contributor.author","Frauendorf, Holm"],["dc.contributor.author","Vana, P."],["dc.date.accessioned","2018-11-07T10:46:04Z"],["dc.date.available","2018-11-07T10:46:04Z"],["dc.date.issued","2004"],["dc.description.abstract","Initiation by tert-butyl peroxypivalate (TBPP), tert-amyl peroxypivalate (TAPP), 1,1,3,3-tetramethylbutyl peroxypivalate (TMBPP), or 1,1,2,2-tetramethylpropyl peroxypivalate (TMPPP) of radical polymerization of methyl methacrylate in toluene solution at 90 degreesC was studied via polymer end-group analysis using electrospray ionization mass spectrometry (ESI-MS). Conclusive peak assignments allowed for measuring the type and concentration of the fragments that actually initiate macromolecular growth after thermal decomposition of these peroxypivalates. It was found that the pivaloyloxy radical moiety undergoes instantaneous decarboxylation to yield an initiating tert-butyl radical. The alkoxy radical moiety, on the other hand, may generate, via P-scission reaction, different types of carbon-centered radicals (together with a ketone) or may undergo a 1,5-H-shift reaction, by which reaction an oxygen-centered radical is transformed into a carbon-centered hydroxy radical. This hydrogen shift reaction was found in case of TMBPP. Surprisingly, no evidence for initiating alkoxy radicals could be found, not even in case of initiation by TBPP, where the intermediate tert-butoxy radical undergoes a rapid chain-transfer reaction with the solvent toluene. (C) 2004 Wiley Periodicals, Inc."],["dc.identifier.doi","10.1002/pola.20264"],["dc.identifier.isi","000223476800016"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/47662"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","0887-624X"],["dc.title","Initiation of free-radical polymerization by peroxypivalates studied by electrospray ionization mass spectrometry"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","8483"],["dc.bibliographiccitation.issue","19"],["dc.bibliographiccitation.journal","Polymer"],["dc.bibliographiccitation.lastpage","8493"],["dc.bibliographiccitation.volume","46"],["dc.contributor.author","Drache, M."],["dc.contributor.author","Schmidt-Naake, G."],["dc.contributor.author","Buback, M."],["dc.contributor.author","Vana, P."],["dc.date.accessioned","2018-11-07T10:55:48Z"],["dc.date.available","2018-11-07T10:55:48Z"],["dc.date.issued","2005"],["dc.description.abstract","Cumyl dithiobenzoate (CDB) mediated methyl acrylate (MA) bulk polymerizations at 80 degrees C, using CDB concentrations between 1.5 X 10(-2) and 5.0 X 10(-2) mol L-1, were modeled via a novel Monte Carlo simulation procedure with respect to experimental time-dependent conversions, X, number average molecular weights, M-n, and weight average molecular weights, M-w, The simulations were based upon individual treatment of 5 X 108 discrete molecules in accordance to their actual reaction pathways. The kinetic scheme employed includes termination reactions of intermediate RAFT radicals with propagating radicals and reaction steps of the RAFT pre-equilibrium, which are different from those of the RAFT main equilibrium. The equilibrium constant of the main equilibrium of the CDB/MA system at 80 degrees C was found to be K= 1.2 X 10(4) L mol(-1), indicating a relatively stable intermediate radical. The concentration of the intermediate RAFT radical, although not employed as experimental input data for the modeling, was calculated by using the obtained set of kinetic parameters as being in excellent agreement with experimental electron spin resonance spectroscopic data. (c) 2005 Elsevier Ltd. All rights reserved."],["dc.identifier.doi","10.1016/j.polymer.2004.11.117"],["dc.identifier.isi","000231573100077"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/49867"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Sci Ltd"],["dc.publisher.place","Oxford"],["dc.relation.conference","IUPAC World Polymer Congress"],["dc.relation.eventlocation","Paris, FRANCE"],["dc.relation.issn","0032-3861"],["dc.title","Modeling RAFT polymerization kinetics via Monte Carlo methods: cumyl dithiobenzoate mediated methyl acrylate polymerization"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","9497"],["dc.bibliographiccitation.issue","23"],["dc.bibliographiccitation.journal","Macromolecules"],["dc.bibliographiccitation.lastpage","9508"],["dc.bibliographiccitation.volume","38"],["dc.contributor.author","Junkers, T."],["dc.contributor.author","Theis, A."],["dc.contributor.author","Buback, M."],["dc.contributor.author","Davis, T. P."],["dc.contributor.author","Stenzel, M. H."],["dc.contributor.author","Vana, P."],["dc.contributor.author","Barner-Kowollik, C."],["dc.date.accessioned","2018-11-07T10:54:20Z"],["dc.date.available","2018-11-07T10:54:20Z"],["dc.date.issued","2005"],["dc.description.abstract","The chain-length dependence of the termination rate coefficient, k(t), in butyl acrylate free-radical polymerization has been determined by two independent methods, RAFT-SP-PLP and RAFT-CLD-T, both employing control of radical chain length by reversible addition fragmentation chain transfer (RAFT) polymerization. Within RAFT-SP-PLP, the polymerization induced by a laser single pulse is monitored via near-IR spectroscopy with a time resolution of microseconds. In RAFT-CLD-T, isothermal reaction rate measurements are carried out via DSC under stationary polymerization conditions. The resulting k(t) data refer to the situation of living/controlled radical polymerization, where both radical chain length and monomer conversion increase during the course of the reaction. The RAFT-SP-PLP measurements were carried out at 60 degrees C and two pressures, 5 and 1000 bar. The RAFT-CLD-T experiments were run at ambient pressure and at two temperatures, 60 and 80 degrees C, respectively. In absolute value, the termination rate coefficients for identical pressure and temperature deduced from the two methods differ by less than a factor of 2. For the dependence of k(t) on chain length, i, almost identical information is provided by the two techniques. The chain-length dependence of kt may be described by the power-law expression k(t)(i) = k(t)(1,1)i(-alpha) with, however, a being different for short-chain and long-chain radicals. RAFT-SP-PLP yields alpha(1) = 1.25 for the short-chain regime from 1 < i < 30, and alpha(2) = 0.22 for chain lengths above i = 50. RAFT-CLD-T results in alpha(1) = 1.04 and alpha(2) = 0.20 in identical chain length regimes. kt(1,1) values are found to be close to 1 x 10(9) L mol(-1) s(-1)."],["dc.identifier.doi","10.1021/ma051485k"],["dc.identifier.isi","000233225600015"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/49541"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","0024-9297"],["dc.title","Chain length dependent termination in butyl acrylate free-radical polymerization studied via stationary and pulsed laser initiated RAFT polymerization"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","2570"],["dc.bibliographiccitation.issue","18"],["dc.bibliographiccitation.journal","Macromolecular Chemistry and Physics"],["dc.bibliographiccitation.lastpage","2582"],["dc.bibliographiccitation.volume","203"],["dc.contributor.author","Buback, M."],["dc.contributor.author","Egorov, M."],["dc.contributor.author","Giess, Rene MarkusGilbert, Robert G."],["dc.contributor.author","Kaminsky, V."],["dc.contributor.author","Olaj, O. F."],["dc.contributor.author","Russell, Gregory T."],["dc.contributor.author","Vana, P."],["dc.contributor.author","Zifferer, G."],["dc.date.accessioned","2018-11-07T09:41:24Z"],["dc.date.available","2018-11-07T09:41:24Z"],["dc.date.issued","2002"],["dc.description.abstract","This is the first publication of an IUPAC-sponsored Task Group on \"Critically evaluated termination rate coefficients for free-radical polymerization.\" The paper summarizes the current situation with regard to the reliability of values of termination rate coefficients k(t). It begins by illustrating the stark reality that there is large and unacceptable scatter in literature values of k(t), and it is pointed out that some reasons for this are relatively easily, remedied. However, the major reason for this situation is the inherent complexity of the phenomenon of termination in free-radical polymerization. It is our impression that this complexity is only incompletely grasped by many workers in the field, and a consequence of this tendency to oversimplify is that misunderstanding of and disagreement about termination are rampant. Therefore this paper presents a full discussion of the intricacies of k(t): sections deal with diffusion control, conversion dependence, chain-length, dependence, steady state and non-steady state measurements, activation energies and activation volumes, combination and disproportionation, and theories. All the presented concepts are developed from first principles, and only rigorous, fully-documented experimental results and theoretical investigations are cited as evidence. For this reason it can be said that this paper summarizes all that we, as a cross-section of workers in the, field, agree on about termination in free-radical polymerization. Our discussion naturally leads to a series of recommendations regarding measurement of k(t) and reaching a more satisfactory understanding of this very important rate coefficient. Variation of termination. rate coefficient k(t) with inverse absolute temperature T-1 for bulk, polymerization of methyl methacrylate at ambient pressure.([6]) The plot contains all methacrylate at ambient pressure. tabulated values([6]) (including those categorized as \"recalculated\") except ones from polymerizations noted as involving. solvent or above-ambient pressures."],["dc.identifier.doi","10.1002/macp.200290041"],["dc.identifier.isi","000181469100005"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/33718"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-v C H Verlag Gmbh"],["dc.relation.issn","1022-1352"],["dc.title","Critically evaluated termination rate coefficients for free-radical polymerization, 1 - The current situation"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1376"],["dc.bibliographiccitation.issue","15"],["dc.bibliographiccitation.journal","Macromolecular Rapid Communications"],["dc.bibliographiccitation.lastpage","1381"],["dc.bibliographiccitation.volume","25"],["dc.contributor.author","Arita, T."],["dc.contributor.author","Buback, M."],["dc.contributor.author","Janssen, O."],["dc.contributor.author","Vana, P."],["dc.date.accessioned","2018-11-07T10:46:28Z"],["dc.date.available","2018-11-07T10:46:28Z"],["dc.date.issued","2004"],["dc.description.abstract","Application of high pressure, up to 2 500 bar, in cumyl dithiobenzoate-mediated styrene reversible addition fragmentation chain transfer (RAFT) polymerizations was found to be extremely advantageous with respect to both rate and control of polymerization. The overall rate of polymerization could be increased by a factor of approximately 3 with, e.g., at 23% conversion, concomitantly reducing the polydispersity indices from 1.35 to 1.10. No significant effect of increased pressure on the rate retardation effect was found."],["dc.identifier.doi","10.1002/marc.200400204"],["dc.identifier.isi","000223163800004"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/47753"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-v C H Verlag Gmbh"],["dc.relation.issn","1022-1336"],["dc.title","RAFT-polymerization of styrene up to high pressure: Rate enhancement and improved control"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","7935"],["dc.bibliographiccitation.issue","19"],["dc.bibliographiccitation.journal","Macromolecules"],["dc.bibliographiccitation.lastpage","7943"],["dc.bibliographiccitation.volume","38"],["dc.contributor.author","Arita, T."],["dc.contributor.author","Buback, M."],["dc.contributor.author","Vana, P."],["dc.date.accessioned","2018-11-07T10:55:44Z"],["dc.date.available","2018-11-07T10:55:44Z"],["dc.date.issued","2005"],["dc.description.abstract","Self-initiated reversible addition fragmentation chain transfer (RAFT) polymerizations of styrene at temperatures of 120, 150, and 180 degrees C, using cumyl dithiobenzoate (CDB) at concentrations between 5.0 x 10(-3) and 2.0 x 10(-2) mol L-1 as the RAFT agent were performed at 1000 bar. The increase of average molecular weight with monomer conversion, the shape of the molecular weight distributions, and polydispersity indices below 1.5 at monomer conversions up to about 50% indicate control of styrene bulk polymerization even at the high experimental temperatures. Neither a substantial decomposition of the RAFT agent nor a change in the overall polymerization process, e.g., by ionic side reactions, is observed. Polymerization rates are lower than in conventional styrene polymerization. The rate retardation effect increases with CDB concentration but is clearly reduced toward higher temperature. The lower retardation effect at high temperatures is assigned to a lower equilibrium concentration of the intermediate RAFT radical. The experimental rate data can be consistently described in terms of the concept of irreversible termination of the intermediate RAFT radical. On the other hand, the data are qualitatively and semiquantitatively inconsistent with the idea of slow fragmentation of intermediate radicals. The analysis of the kinetic data results in a reaction enthalpy of about 50 M mol(-1) for the beta-scission reaction of the intermediate RAFT radical."],["dc.identifier.doi","10.1021/ma051012d"],["dc.identifier.isi","000231897900011"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/49854"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","0024-9297"],["dc.title","Cumyl dithiobenzoate mediated RAFT polymerization of styrene at high temperatures"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]