The Importance of Exchange Reactions in Controlled/Living Radical Polymerization in the Presence of Alkoxyamines and Transition Metals.
Abstract
The role of exchange reactions in controlled/living radical polymerizations is analyzed. Styrene polymerization in the presence TEMPO and atom transfer radical polymerization (ATRP) catalyzed by transition metals (Cu(II)X2/2Bipy complex) are compared. ATRP proceeds approximately one order of magnitude faster than TEMPO-moderated polymerization due to a higher stationary concentration of radicals and an equilibrium more shifted to the side of radicals. ATRP can provide better defined polymers with polydispersities down to Mw/Mn approx.= l.05. This fact can he ascribed to a faster deactivation process and a smaller contribution of side reactions. The polydispersities in both systems are defined by the relative rates of the deactivation and propagation processes. The rate constant of deactivation of growing polystyryl radicals by TEMPO is in the range of kd=10(exp 8) L/mol/s, which is substantially higher than the previously reported value.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 12, 1996
- Accession Number
- ADA309796
Entities
People
- Krzysztof Matyjaszewski
Organizations
- Carnegie Mellon University