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Leveled Steric Effect in Alkoxyamines of SG1‐Type
Author(s) -
Acerbis Sébastien,
Beaudoin Emmanuel,
Bertin Denis,
Gigmes Didier,
Marque Sylvain,
Tordo Paul
Publication year - 2004
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200300240
Subject(s) - homolysis , steric effects , chemistry , polymerization , reaction rate constant , nitroxyl , nitroxide mediated radical polymerization , bond cleavage , photochemistry , stereochemistry , radical polymerization , radical , kinetics , organic chemistry , polymer , catalysis , quantum mechanics , physics
Summary: During nitroxide mediated polymerization (NMP) the polymerization time decreases with the increasing rate constant of the cleavage of the NOC bond of the dormant alkoxyamines. Hence, the knowledge of the factors influencing this cleavage is of considerable interest. Recently, we demonstrated that the influence of the nitroxyl moieties of 24 alkoxyamines on the values of the rate constant for the homolysis of the CON bond of the alkoxyamine ( k d ) was accounted for by a biparametric equation log k d = −3.07 × σ U − 0.88 × E s − 5.88, with σ U for the universal electrical effect and E s for the steric demand of the substituents bound to the nitroxyl function. During the course of the work, it was assumed for a number of molecules that the steric effect was leveled. We present herein three new SG1‐based alkoxyamines with sufficiently different steric strains to confirm the leveled steric effect.The fit of the rate constant for the homolysis of the CON bond of the alkoxyamines ( k d s) with the equation log k d = −0.37 × σ U − 0.88 × E s when a leveled steric effect is assumed.