Modeling the Influence of Diffusion-Controlled Reactions and Residual Termination and Deactivation on the Rate and Control of Bulk ATRP at High Conversions
| Autor: | Ali Mohammad Rabea, Shiping Zhu |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2015 |
| Předmět: |
Kinetic chain length
Polymers and Plastics Radical diffusion-controlled reactions Radical polymerization 02 engineering and technology ATRP radical deactivation 010402 general chemistry Photochemistry 01 natural sciences lcsh:QD241-441 lcsh:Organic chemistry Chemistry Atom-transfer radical-polymerization high conversion modeling General Chemistry dormant chain activation 021001 nanoscience & nanotechnology Chain termination radical termination 0104 chemical sciences Polymerization Cobalt-mediated radical polymerization Living polymerization monomer propagation 0210 nano-technology |
| Zdroj: | Polymers, Vol 7, Iss 5, Pp 819-835 (2015) Polymers Volume 7 Issue 5 Pages 819-835 |
| ISSN: | 2073-4360 |
| Popis: | In high-conversion atom transfer radical polymerization (ATRP), all the reactions, such as radical termination, radical deactivation, dormant chain activation, monomer propagation, etc. could become diffusion controlled sooner or later, depending on relative diffusivities of the involved reacting species. These diffusion-controlled reactions directly affect the rate of polymerization and the control of polymer molecular weight. A model is developed to investigate the influence of diffusion-controlled reactions on the high conversion ATRP kinetics. Model simulation reveals that diffusion-controlled termination slightly increases the rate, but it is the diffusion-controlled deactivation that causes auto-acceleration in the rate (“gel effect”) and loss of control. At high conversions, radical chains are “trapped” because of high molecular weight. However, radical centers can still migrate through (1) radical deactivation–activation cycles and (2) monomer propagation, which introduce “residual termination” reactions. It is found that the “residual termination” does not have much influence on the polymerization kinetics. The migration of radical centers through propagation can however facilitate catalytic deactivation of radicals, which improves the control of polymer molecular weight to some extent. Dormant chain activation and monomer propagation also become diffusion controlled and finally stop the polymerization when the system approaches its glass state. |
| Databáze: | OpenAIRE |
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