Chain length dependent termination rate coefficients of methyl methacrylate (MMA) in the gel regime: Accessing k(t)(i,i) using reversible addition-fragmentation chain transfer (RAFT) polymerization

Johnston-Hall, Geoffrey, Stenzel, Martina H., Davis, Thomas P., Barner-Kowollik, Christopher and Monteiro, Michael J. (2007) Chain length dependent termination rate coefficients of methyl methacrylate (MMA) in the gel regime: Accessing k(t)(i,i) using reversible addition-fragmentation chain transfer (RAFT) polymerization. Macromolecules, 40 8: 2730-2736. doi:10.1021/ma062405v


Author Johnston-Hall, Geoffrey
Stenzel, Martina H.
Davis, Thomas P.
Barner-Kowollik, Christopher
Monteiro, Michael J.
Title Chain length dependent termination rate coefficients of methyl methacrylate (MMA) in the gel regime: Accessing k(t)(i,i) using reversible addition-fragmentation chain transfer (RAFT) polymerization
Formatted title
Chain length dependent termination rate coefficients of methyl methacrylate (MMA) in the gel regime: Accessing kti,i using reversible addition-fragmentation chain transfer (RAFT) polymerization
Journal name Macromolecules   Check publisher's open access policy
ISSN 0024-9297
Publication date 2007-01-21
Sub-type Article (original research)
DOI 10.1021/ma062405v
Volume 40
Issue 8
Start page 2730
End page 2736
Total pages 7
Place of publication Washington D.C., USA
Publisher American Chemical Society
Collection year 2008
Language eng
Subject 250504 Polymerisation Mechanisms
C1
780103 Chemical sciences
Abstract The termination rate coefficient, k(t)(i,i), for propagating chains of near equal length, i, was evaluated using the RAFT-CLD-T method over a wide range of chain lengths and up to a conversion of 70% for MMA polymerizations carried out in the presence of the RAFT agent, CPDB, at 80 degrees C. We found that the conversion for the gel onset corresponded to the conversion at which polymer chains begin to overlap (i.e., c*), and was found to range from 15 to 30% conversion depending on the M-n. It was further shown that c* also corresponded with the gel onset conversions for vinyl acetate and methyl acrylate. The chain length dependence of k(t) in the gel regime scaled as alpha(gel)(x) = 1.8x + 0.056, suggesting that reptation alone does not play a role in our system. A composite model was then derived to accurately describe k(t)(i,i) for chain lengths up to 3200 and conversions up to 70%. The k(t)(i,i) profiles for well-known termination models were tested and most gave unsatisfactory agreement with our experiments. Our model can be readily applied to any monomer provided accurate k(t)(i,i)(x) data can be determined.
Keyword Polymer Science
Free-radical Polymerization
Diffusion-controlled Polymerization
High-conversion Polymerization
Evaluated Rate Coefficients
Rate-constant
Initiator Efficiencies
Pressure-dependence
Rate Retardation
Butyl Acrylate
Kinetics
Q-Index Code C1
Q-Index Status Confirmed Code

 
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Created: Mon, 18 Feb 2008, 16:49:21 EST