Influence of Monomer Structure on the Propagation Kinetics of Acrylate and Methacrylate Homopolymerizations Studied via PLP-SEC in Fluid CO2
✍ Scribed by Sabine Beuermann; Michael Buback; Véronique El Rezzi; Michael Jürgens; Dorit Nelke
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 145 KB
- Volume
- 205
- Category
- Article
- ISSN
- 1022-1352
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✦ Synopsis
Abstract
Summary: Propagation kinetics of free‐radical homopolymerizations of methyl acrylate, dodecyl acrylate, butyl methacrylate, dodecyl methacrylate, glycidyl methacrylate, cyclohexyl methacrylate, and isobornyl methacrylate in solutions containing 40 wt.‐% CO~2~ were studied applying the PLP‐SEC technique. The obtained apparent propagation rate coefficients, k~p,app~, are by up to 40% below the associated bulk k~p~ values. This reduction is assigned to a lowering of local monomer concentration, c~M,loc~, at the site of the free‐radical chain end rather than to a decrease of the actual propagation rate coefficient. With the alkyl (meth)acrylates, intersegmental interactions between polar groups of the same polymer molecule are responsible for deviations of c~M,loc~ from the analytical overall monomer concentration, c~M,a~. Increasing size of the flexible alkyl ester group reduces the differences between c~M,loc~ and c~M,a~ due to shielding effects. Methacrylates with cyclic ester groups do not follow this trend. In case of isobornyl methacrylate, which polymerizes to a rigid material with large side groups, relative size of monomer and CO~2~ matters and reduces c~M,loc~ significantly below c~M,a~.
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