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The carbenium ion ‐ oxonium ion exchange processes related to vinyl and ring‐opening polymerization
Author(s) -
Penczek Stanislaw,
Szymanski Ryszard
Publication year - 1992
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19920600108
Subject(s) - oxonium ion , cationic polymerization , chemistry , polymerization , trifluoromethanesulfonate , living cationic polymerization , carbenium ion , polymer chemistry , onium , ion , covalent bond , vinyl ether , ring opening polymerization , organic chemistry , copolymer , catalysis , polymer
It has previously been proposed (Ref. 1) that in the cationic vinyl polymerizations, proceeding with termination due to the collapse of ion pairs, addition of bases increases “livingness”, because of the fast convertion of the otherwise dead (within the time of polymerization) covalent species into the onium ions; these, in turn, fast convert into carbenium ions, the actually propagating species. Equilibria between carbenium ions (CH 3 OCH 2 + A − has been used as a model) and their onium counterparts ((CH 3 ) 2 O taken as a model base) as well as between covalent species (CH 3 OCH 2 OSO 2 CF 3 ) and the corresponding oxonium ion (with a (CH 3 ) 2 O ligand) have been studied by dynamic 1 H and 19 F NMR. Total ionization of methoxymethyl triflate (CH 3 OCH 2 OSO 2 CF 3 ) has been shown to increase indeed from 10 4 (‐10°C) to 10 6 (‐70°C) times when 1,0 mol·L −1 of (CH 3 ) 2 O is added. Although this model system better describes polymerization of cyclic acetals than that of vinyl ethers, it shows at least qualitatively the importance of bases in ionization of covalent species, which may be responsible for reinitiation in the cationic polymerization of vinyl ethers.