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About the various types of transfer reactions in the cationic polymerization of isobutyl vinyl ether
Author(s) -
Leleu J.M.,
Bernardo V.,
Polton A.,
Tardi M.,
Sigwalt P.
Publication year - 1995
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.1995.210370311
Subject(s) - chemistry , cationic polymerization , monomer , polymerization , polymer chemistry , vinyl ether , chain transfer , toluene , reaction rate , solvent , stoichiometry , vinyl acetate , ether , radical polymerization , organic chemistry , polymer , copolymer , catalysis
For isobutyl vinyl ether (IBVE) polymerizations made in the presence of large concentrations of an electron donor such as ethyl acetate (EA), e.g. 0.5 M, evidence for transfer reactions of zero order in monomer concentration has been given earlier. In the present paper, the changes in the transfer processes according to the ester concentration are examined. Polymerizations were made under vacuum at 0°C in toluene. Solvent and monomer were dried over sodium films. Two initiating systems were used. Initiation with trityl tetrachloroaluminate (2.5 × 10 −5 −2 × 10 −4 M) gave very fast reactions, which were stopped at various yields and showed that transfer of first order in [M] is the main transfer reaction (with k trM / k p at 0°C). The addition of a small amount of EA (5 × 10 −2 M) lowers the reaction rate considerably but leads only to a small reduction of k trM / k p (to 5·6 × 10 −4 ). Initiation with isobutyl‐1‐chloroethylether (IBCE) and an excess of aluminium trichloride ([AlCl 3 ]/[IBCE] ≃ 10) was made in the presence of increasing amounts of EA. This lowers the propagation rate (first order in [M]). For [M] 0 /[I] 0 ratios lower than 300, the linearity of M̄ n with yield is observed (‘living’ polymerization) but a strong deviation occurs for higher [M] 0 /[I] 0 . The linear increase with reaction time of the concentration [N] of macromolecules resulting from transfer is in agreement with a preponderant transfer of zero order in [M]. Transfer to monomer is considerably reduced. The relative importance of transfer of zero order in [M] increases with [EA], and it involves mainly ethyl acetate. The reduction of direct transfer to monomer in the presence of high concentrations of ethyl acetate is explained by a propagation mechanism involving monomer solvated cationic active species, in equilibrium with inactive species solvated only by ethyl acetate.