Critically-Evaluated Propagation Rate Coefficients in Free Radical Polymerizations I. Styrene and Methyl Methacrylate

Gilbert, Robert G.; Buback, Michael; Davis, Thomas P.; Fukuda, Takeshi; Hill, D. J. T.; Beuennann, S.; Hutchinson, Robin A.; Jenluns, A.; Johnson, A. F.; Kamachi, M.; Kaminsky, V. A.; Keight, D.V.; Klumperman, Bert; Lachinov, M. B.; Madruga, Enrique López; Manders, Bart G.; Maschio, Giuseppe; Moad, Graeme; Nomura, Mamoru; O'Driscoll, KF; Olaj, F.; Padget, J. C.; Pla, Fernand; Russell, Gregory T.; Schweer, Johannes; Shen, Jinbo; Stickler, Manfred; Westmoreland, David G.; Yamada, Bunichiro

doi:10.1515/iupac.68.3270

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“…The pre-exponential, A(k p ), of DBI is by several orders of magnitude below the numbers for acrylates, 17 vinyl esters, 18−20 and styrene 21,22 which, e.g., are A(k p ) = 1.66 × 10 7 L mol −1 s −1 for methyl acrylate, A(k p ) = 1.47 × 10 7 L mol −1 s −1 for vinyl acetate, and A(k p ) = 4.27 × 10 7 L mol −1 s −1 for styrene bulk polymerizations. The low A(k p ) of DBI demonstrates the large a Tabulated is the measured overall monomer-to-polymer conversion, X ov , the associated conversion per laser single pulse, X SP , and the monomer-topolymer conversion, X, obtained from X SP under consideration of the amount of DBI required for the production of the initial DBI radical.…”

Section: ■ Experimental Partmentioning

confidence: 90%

Propagation and Chain-Length-Dependent Termination Rate Coefficients Deduced from a Single SP–PLP–EPR Experiment

Kattner

Buback

2016

Macromolecules

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The laser single pulse (SP)−pulsed laser polymerization (PLP)−electron paramagnetic resonance (EPR) technique allows for deducing propagation (k p ) and termination (k t ) rate coefficients, including the chain-length dependence of k t , from a single pulsed-laser experiment. The method, which is particularly well suited for slowly terminating radicals, e.g., sterically hindered and ionic radicals, is illustrated for di(n-butyl) itaconate in bulk at temperatures from 30 to 60 °C. The time evolution of the DBI radical concentration is measured with a high time resolution at constant magnetic field. Propagation is associated with a relatively low pre-exponential A(k p ), which is responsible for the small k p value of 6.8 L mol −1 s −1 at 30 °C. The chain-length dependence (CLD) of k t , deduced from the same SP− PLP−EPR signal as is k p , turns out to be adequately represented by the composite model. Whereas typical numbers are found for the power-law exponents for short and long radicals and for the crossover chain length, the parameter k t (1,1), which represents mutual termination of two radicals of chain length unity, is by 2 orders of magnitude below k t (1,1) of monomers without significant steric hindrance. Article pubs.acs.org/Macromolecules

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Section: ■ Experimental Partmentioning

confidence: 90%