Accession Number : ADA309796

Title :   The Importance of Exchange Reactions in Controlled/Living Radical Polymerization in the Presence of Alkoxyamines and Transition Metals.

Descriptive Note : Technical rept.,

Corporate Author : CARNEGIE-MELLON UNIV PITTSBURGH PA DEPT OF CHEMISTRY

Personal Author(s) : Matyjaszewski, Krzysztof

PDF Url : ADA309796

Report Date : 12 JUN 1996

Pagination or Media Count : 19

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.

Descriptors :   *POLYMERIZATION, *STYRENES, TRANSITION METALS, EXCHANGE REACTIONS, REACTION KINETICS, ORGANOMETALLIC COMPOUNDS, COPPER COMPOUNDS, CHEMICAL RADICALS, DEACTIVATION, SIDE REACTIONS.

Subject Categories : Polymer Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE