Buback, Michael M.

[["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","1805"],["dc.bibliographiccitation.issue","21"],["dc.bibliographiccitation.journal","Macromolecular Rapid Communications"],["dc.bibliographiccitation.lastpage","1811"],["dc.bibliographiccitation.volume","30"],["dc.contributor.author","Barth, Johannes"],["dc.contributor.author","Buback, Michael"],["dc.date.accessioned","2018-11-07T11:22:18Z"],["dc.date.available","2018-11-07T11:22:18Z"],["dc.date.issued","2009"],["dc.description.abstract","Termination kinetics of methyl methacrylate (MMA) bulk. polymerization has been studied via the single pulsed laser polymerization-electron paramagnetic resonance method. MMA-d(8) has been investigated to enhance the signal-to-noise quality of microsecond time-resolved measurement of radical concentration. Chain-length-dependent termination rate coefficients of radicals of identical size k(t)(i,i), are reported for 5-70 degrees C and up to i = 100. k(t)(i,i) decreases according to the power-law expression k(t)(i,i) = k(t)(1,1).i(-alpha). At 5 degrees C, k(t) for two MMA radicals of chain-length unity is k(t)(1,1) = (5.8 +/- 1.3) . 10(8)L . mol(-1) . s(-1). The associated activation energy and power-law exponent are: E(A)(k(t)(1,1)) approximate to 9 +/- 2 kJ . mol(-1) and alpha approximate to 0.63 +/- 0.15, respectively."],["dc.identifier.doi","10.1002/marc.200900335"],["dc.identifier.isi","000271990300004"],["dc.identifier.pmid","21638457"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/55965"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-v C H Verlag Gmbh"],["dc.relation.issn","1022-1336"],["dc.title","SP-PLP-EPR Investigations into the Chain-Length-Dependent Termination of Methyl Methacrylate Bulk Polymerization"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","481"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Macromolecules"],["dc.bibliographiccitation.lastpage","488"],["dc.bibliographiccitation.volume","42"],["dc.contributor.author","Barth, Johannes"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Hesse, Pascal"],["dc.contributor.author","Sergeeva, Tatiana"],["dc.date.accessioned","2018-11-07T08:33:26Z"],["dc.date.available","2018-11-07T08:33:26Z"],["dc.date.issued","2009"],["dc.description.abstract","The chain-length dependence of the termination rate coefficient, k(t), of bulk homopolymerizations of n-butyl methacrylate (n-BMA) and tert-butyl methacrylate (t-BMA) at ambient pressure and temperatures between -30 and 60 degrees C has been studied via the single pulse-pulsed laser polymerization-electron spin resonance (SP-PLP-ESR) technique. The decay of radical concentration, c(R), after laser SP initiation is monitored with a high time resolution of microseconds by ESR spectroscopy. Radical chain length, i, increases linearly with time t after applying the laser pulse. The experimental k(t)(i,i) values refer to rate coefficients for termination of two radicals of identical chain length i. The variation of k(t)(i,i) with chain length is adequately represented via the composite model proposed by Smith et al., in which two power-law expressions, k(t)(i-i) proportional to i(-alpha), are contained with the exponents alpha(s) and alpha(l) referring to short-chain and long-chain radicals, respectively. The transition between the two regimes occurs at the crossover chain length, i(c). The rate coefficients extrapolated for termination of two radicals of chain length unity. k(t)(l,l), are almost identical for n-BMA and t-BMA with an activation energy of E-A(k(t)(l,l)) approximate to 10 kJ mol(-1). The alpha(s) values are close to each other 0.65 +/- 0.10 (n-BMA) and 0.56 +/- 0.10 (t-BMA). Both alpha(l) values are found to be 0.20 +/- 0.05, which is close to the theoretical value of alpha(l), = 0.16. The crossover chain lengths are i(c) approximate to 50 for n-BMA and i(c) approximate to 70 for t-BMA. The minor differences in composite-model parameter values of n-BMA and t-BMA are assigned to differences in chain mobility."],["dc.identifier.doi","10.1021/ma802078g"],["dc.identifier.isi","000262625200003"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/17576"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","1520-5835"],["dc.relation.issn","0024-9297"],["dc.title","Chain-Length-Dependent Termination in n-Butyl Methacrylate and tert-Butyl Methacrylate Bulk Homopolymerizations Studied via SP-PLP-ESR"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1292"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","Macromolecules"],["dc.bibliographiccitation.lastpage","1297"],["dc.bibliographiccitation.volume","44"],["dc.contributor.author","Barth, Johannes"],["dc.contributor.author","Buback, Michael"],["dc.date.accessioned","2018-11-07T08:58:03Z"],["dc.date.available","2018-11-07T08:58:03Z"],["dc.date.issued","2011"],["dc.description.abstract","The termination kinetics of methacrylic acid (MAA) radical polymerization in aqueous solution containing 10 wt % MAA was measured via the single pulse-pulsed laser polymerization-electron paramagnetic resonance (SP-PLP-EPR) method from 0 to 50 degrees C. The termination rate coefficient, k(u) was determined as a function of radical chain length. Addition of high-molecular-mass poly(methacrylic acid), which mimicks monomer conversion, leads to a reduction of k(u), which is however far below the associated decrease in fluidity, eta(-1)."],["dc.description.sponsorship","Fonds der Chemischen Industrie; BASF SE"],["dc.identifier.doi","10.1021/ma102278n"],["dc.identifier.isi","000288289700014"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/23548"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","0024-9297"],["dc.title","SP-PLP-EPR Study into the Termination Kinetics of Methacrylic Acid Radical Polymerization in Aqueous Solution"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","5708"],["dc.bibliographiccitation.issue","24"],["dc.bibliographiccitation.journal","Polymer"],["dc.bibliographiccitation.lastpage","5712"],["dc.bibliographiccitation.volume","50"],["dc.contributor.author","Barth, Johannes"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Schmidt-Naake, Gudrun"],["dc.contributor.author","Woecht, Inga"],["dc.date.accessioned","2018-11-07T11:22:02Z"],["dc.date.available","2018-11-07T11:22:02Z"],["dc.date.issued","2009"],["dc.description.abstract","Termination rate coefficients, k(t), for free-radical polymerization of 15 vol.-% methyl methacrylate (MMA) dissolved in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-imide and in 1-butyl-3-methylimidazolium tetrafluoroborate were measured at 10 degrees C via the single pulse-pulsed laser polymerization electron paramagnetic resonance (SP-PLP-EPR) technique. Whereas absolute k(t) in ionic liquid solution is by about one order of magnitude below the associated bulk MMA value, the chain-length dependence of k(t) is very similar in both liquid environments. (C) 2009 Elsevier Ltd. All rights reserved."],["dc.description.sponsorship","Deutsche Forschungsgemeinschaft; Fonds der Chemischen Industrie"],["dc.identifier.doi","10.1016/j.polymer.2009.09.065"],["dc.identifier.isi","000272124900013"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/55911"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Sci Ltd"],["dc.relation.issn","0032-3861"],["dc.title","Termination kinetics of free-radical polymerization in ionic liquids"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1366"],["dc.bibliographiccitation.issue","13"],["dc.bibliographiccitation.journal","Macromolecular Chemistry and Physics"],["dc.bibliographiccitation.lastpage","1378"],["dc.bibliographiccitation.volume","212"],["dc.contributor.author","Barth, Johannes"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Russell, Gregory T."],["dc.contributor.author","Smolne, Sebastian"],["dc.date.accessioned","2018-11-07T08:54:42Z"],["dc.date.available","2018-11-07T08:54:42Z"],["dc.date.issued","2011"],["dc.description.abstract","The technique of SPPLP EPR, which is single-pulse pulsed-laser polymerization (SPPLP) in conjunction with electron paramagnetic resonance (EPR) spectroscopy, is used to carry out a detailed investigation of secondary (chain-end) radical termination of acrylates. Measurements are performed on methyl acrylate, n-butyl acrylate, and dodecyl acrylate in bulk and in toluene solution at -40 degrees C. The reason for the low temperature is to avoid formation of mid-chain radicals (MCRs), a complicating factor that has imparted ambiguity to the results of previous studies of this nature. Consistent with these previous studies, composite-model behavior for chain-length-dependent termination (CLDT) rate coefficients, k(t)(i,i), is found in this work. However, lower and more reasonable values of as, the exponent for variation of k(t)(i,i) at short chain lengths, are found in the present study. Most likely this is because of the absence of MCRs, thereby validating the methodology of this work. Family-type termination behavior is observed, with the following average parameter values adequately describing all results, regardless of acrylate or the presence of toluene: alpha(s) = 0.79, alpha(1) = 0.21 (long chains) and i(c) approximate to 30 (crossover chain length). All indications are that these values carry over to termination of acrylate chain-end radicals at higher, more practical temperatures. Further, these values largely make sense in terms of what is understood about the physical meaning of the parameters. Variation of the rate coefficient for termination between monomeric radicals, k(t)(1,1), is found to be well described by the simple Smoluchowski and Stokes-Einstein equations. This allows easy prediction of k(t)(1,1) for different alkyl acrylates, solvent, and temperature. Through all this the unrivalled power of SPPLP EPR for measuring and understanding (chain-length-dependent) termination rate coefficients shines through."],["dc.description.sponsorship","Fonds der Chemischen Industrie"],["dc.identifier.doi","10.1002/macp.201000781"],["dc.identifier.isi","000292541600005"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/22733"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-v C H Verlag Gmbh"],["dc.relation.issn","1022-1352"],["dc.title","Chain-Length-Dependent Termination in Radical Polymerization of Acrylates"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","4740"],["dc.bibliographiccitation.issue","22"],["dc.bibliographiccitation.journal","Journal of Polymer Science Part A Polymer Chemistry"],["dc.bibliographiccitation.lastpage","4748"],["dc.bibliographiccitation.volume","50"],["dc.contributor.author","Barth, Johannes"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Barner-Kowollik, Christopher"],["dc.contributor.author","Junkers, Thomas"],["dc.contributor.author","Russell, Gregory T."],["dc.date.accessioned","2018-11-07T09:03:29Z"],["dc.date.available","2018-11-07T09:03:29Z"],["dc.date.issued","2012"],["dc.description.abstract","The termination of model mid-chain radicals (MCRs), which mimic radicals that occur in acrylate polymerization over a broad range of reaction conditions, has been studied by single-pulse pulsed laser polymerization (SP-PLP) in conjunction with electron paramagnetic resonance spectroscopy. The model radicals were generated by initiator-fragment addition to acrylic macromonomers that were preformed prior to the kinetic experiments, thus enabling separation of termination from the propagation reaction, for these model radicals propagate sparingly, if at all, on the timescale of SP-PLP experiments. Termination rate coefficients of the MCRs were determined in the temperature range of 060 degrees C in acetonitrile and butyl propionate solution as well as in bulk macromonomer over the range of 0100 degrees C. Termination rate coefficients slightly below those of the corresponding secondary radicals were deduced, demonstrating the relatively high termination activity of this species, even when undergoing MCRMCR termination. For chain length of 10, a reduction by a factor of 6 is observed. Unusually high activation energies were found for the termination rate coefficient in these systems, with 35 kJ mol-1 being determined for bulk macromonomer. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012"],["dc.description.sponsorship","Fonds der Chemischen Industrie; Fonds Wetenschappelijk Onderzoek (FWO)"],["dc.identifier.doi","10.1002/pola.26295"],["dc.identifier.isi","000309925000017"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/24908"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-blackwell"],["dc.relation.issn","0887-624X"],["dc.title","Single-pulse pulsed laser polymerization-electron paramagnetic resonance investigations into the termination kinetics of n-butyl acrylate macromonomers"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","288"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","Macromolecular Reaction Engineering"],["dc.bibliographiccitation.lastpage","301"],["dc.bibliographiccitation.volume","4"],["dc.contributor.author","Barth, Johannes"],["dc.contributor.author","Buback, Michael"],["dc.date.accessioned","2018-11-07T08:43:15Z"],["dc.date.available","2018-11-07T08:43:15Z"],["dc.date.issued","2010"],["dc.description.abstract","Single pulse pulsed laser polymerization electron paramagnetic resonance (SP-PLP-EPR) has been introduced as a powerful method for the very detailed analysis of termination kinetics. During polymerization an intense laser pulse is applied in order to almost instantaneously produce a burst of radicals. The decay of radical concentration is measured by highly time-resolved EPR and is analyzed with respect to the rate coefficients for the termination of two radicals of identical size. SP-PLP-EPR experiments have been carried out for an itaconate monomer, for several methacrylates in bulk and in a solution of ionic liquids, for methacrylic acid in aqueous solution, and for the solution polymerization of butyl acrylate in toluene at low temperature. The data fully support the composite model, which assumes a stronger chain-length dependence of termination for radicals of smaller size and a weaker one for large radicals. The SP-PLP-EPR technique is also applicable in systems with more than one type of growing radicals, as is the case with butyl acrylate polymerization at higher temperature and with RAFT polymerizations, where the novel method may be used for a comprehensive kinetic analysis."],["dc.identifier.doi","10.1002/mren.200900066"],["dc.identifier.isi","000277918200001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/19916"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-v C H Verlag Gmbh"],["dc.relation.issn","1862-832X"],["dc.title","SP-PLP-EPR - A Novel Method for Detailed Studies into the Termination Kinetics of Radical Polymerization"],["dc.type","review"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","5843"],["dc.bibliographiccitation.issue","15"],["dc.bibliographiccitation.journal","Macromolecules"],["dc.bibliographiccitation.lastpage","5845"],["dc.bibliographiccitation.volume","44"],["dc.contributor.author","Liang, Kun"],["dc.contributor.author","Hutchinson, Robin A."],["dc.contributor.author","Barth, Johannes"],["dc.contributor.author","Samrock, Stephan"],["dc.contributor.author","Buback, Michael"],["dc.date.accessioned","2018-11-07T08:53:17Z"],["dc.date.available","2018-11-07T08:53:17Z"],["dc.date.issued","2011"],["dc.identifier.doi","10.1021/ma201391t"],["dc.identifier.isi","000293353800002"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/22371"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","0024-9297"],["dc.title","Reduced Branching in Poly(butyl acrylate) via Solution Radical Polymerization in n-Butanol"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","51"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Macromolecules"],["dc.bibliographiccitation.lastpage","54"],["dc.bibliographiccitation.volume","43"],["dc.contributor.author","Barth, Johannes"],["dc.contributor.author","Buback, Michael"],["dc.contributor.author","Meiser, Wibke"],["dc.contributor.author","Vana, Philipp"],["dc.date.accessioned","2018-11-07T08:46:47Z"],["dc.date.available","2018-11-07T08:46:47Z"],["dc.date.issued","2010"],["dc.description.abstract","A method is presented for determination of reliable values of the equilibrium constant K(eq) between propagating radicals (P(center dot)) and intermediate radicals (INT(center dot)) in reversible addition-fragmentation chain transfer (RAFT) polymerization. The technique is based oil EPR measurement of the ratio of concentrations of the two radical species Under quasi-equilibrium conditions ill low RAFT agent contents. The method requires no calibration of the EPR Setup for absolute radical concentration measurement. [Data for butyl acrylate polymerization mediated by benzyl propyl trithiocarbonate are presented. The value Of K(eq) at - 40 degrees C was determined to be (1.0 +/- 0.1) x 10(4) L mol(-1)."],["dc.description.sponsorship","Fonds der Chemischen Industrie"],["dc.identifier.doi","10.1021/ma902111z"],["dc.identifier.isi","000273268700010"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/20781"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","0024-9297"],["dc.title","Easy Access to the RAFT Equilibrium Constant"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]