Premium
Can Propagation Reaction in Carbocationic Polymerization and Copolymerization of Styrene be Diffusion Controlled ?
Author(s) -
Sigwalt Pierre,
Moreau Michel
Publication year - 2011
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.201151008
Subject(s) - styrene , copolymer , reactivity (psychology) , monomer , nucleophile , polymerization , reaction rate constant , chemistry , carbocation , polymer chemistry , diffusion , polymer , kinetics , thermodynamics , medicinal chemistry , organic chemistry , catalysis , physics , medicine , alternative medicine , pathology , quantum mechanics
Summary: The reactivity ratios r 1 and r 2 in copolymerizations of styrene and para substituted styrenes, for which r 1 = 1/ r 2 , are in contradiction with diffusion control for their propagation reactions. The cross propagation rate constants k 12 copol in copolymerization of styrene with p ‐chlorostyrene, p ‐methylstyrene and p ‐methoxystyrene have been shown to increase with their nucleophilicity parameter N. This is also not compatible with diffusion controlled cross propagation and propagation, but agrees with similar rate constants of propagation for these monomers. The capping rate constants k 12 capp of reactions of poly( p ‐methylstyrene) ± and poly( p ‐methoxystyrene) ± with π‐nucleophiles also increase with N, but with a much larger selectivity. This shows that k 12 copol and k 12 capp are not identical. The k p ± , from 10 9 to 6 10 9 L mol −1 s −1 , obtained with p ‐chlorostyrene, styrene and p ‐methylstyrene by the Diffusion Clock (DC) method are not consistent with those derived from the ionic species concentration (ISC method) for indene, 2,4,6‐trimethylstyrene and p ‐methoxystyrene of the order of 10 4 – 10 5 L mol −1 s −1 , also measured for living polymerization. These last values are in agreement with those measured previously in nonliving systems, and with an approximate compensation between the reactivity of a monomer and that of the corresponding carbocation.