Kinetics of ionic processes in the radiolysis of liquids. V. Cationic polymerization of isobutylene under anhydrous conditions

Taylor, Robert B.; Williams, Ffrançon

doi:10.1021/ja01042a007

Cited by 45 publications

(26 citation statements)

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“…However, this value implies 100% efficiency for all encounters of C + and Nu. Although this may be the case for charged unpaired species of opposite signs such as P n + and the solvated electron (e.g., in radiation initiated polymerization k diff = 9.3 × 10 11 L mol −1 s −1 50) or Br − (or Cl − ) in photoinitiated polymerizations25 this is already less likely for a reaction between monomer and unpaired cations and still more doubtful for the reaction with ion‐pairs (dipole‐dipole reactions).…”

Section: Diffusion Control and Ep = 0 In Capping Or Propagation Reactmentioning

confidence: 99%

Reactivities of carbocations and monomers in carbocationic polymerization and copolymerization

Sigwalt

Moreau

2010

J. Polym. Sci. A Polym. Chem.

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In carbocationic polymerization and copolymerization, a recent publication concluded that the substituent effect on carbocation reactivity is much larger than its effect on monomer reactivity, and this by a factor 106 in the case of the rate constant k12capp for p‐methylstyrene addition (monomer M2) on, respectively, poly(p‐methoxystyrene)± or poly(p‐methylstyrene)± (M 1±). This conclusion is disputed, as well as the assumption that the rate constants of capping (k12capp) obtained in deactivation reactions of poly(p‐methoxystyrene)± are identical with cross propagation rate constants in copolymerization (k12copol). It is shown that the large calculated k12capp are based on propagation constant values for p‐methylstyrene (k p± ≈ 109) obtained by the diffusion‐clock method. They are 104 times smaller as found for all styrenes, that is, between 104 and 105 when they are based on the ionic species concentrations. In such a case, the available data are still in agreement with an approximate compensation between the reactivities of a monomer and of the corresponding carbocation. It is also shown that copolymerization data for styrenes are not compatible with k p± values near to diffusion control, and that variations of log k12capp and log k12copol with the nucleophilicity parameter N of the monomers indicate a much lower selectivity of the monomers in the case of copolymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2666–2680, 2010

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Section: Diffusion Control and Ep = 0 In Capping Or Propagation Reactmentioning

confidence: 99%

Reactivities of carbocations and monomers in carbocationic polymerization and copolymerization

Sigwalt

Moreau

2010

J. Polym. Sci. A Polym. Chem.

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“…33 This is a free-ion constant, k p ϩ , because at the aforementioned ionic concentrations, no ion pairing is possible. Isobutene cannot be polymerized by anionic or freeradical methods but does polymerize rapidly at low temperatures with standard cationic initiators, which lends credence to the mechanism.…”

Section: Cationic Polymerizationmentioning

confidence: 99%

“…The three very high propagation constants (k p ϩ ) depend on ␥-radiation-based experiments in bulk monomers, cyclopentadiene, 64a styrene, 31 and isobutene. 33 These can be eliminated from consideration in comparisons with other systems if we believe that Plesch 42 was correct and that the k p 's derived from bulk monomers are not the normal bimolecular constants. His evidence is, however, not entirely convincing because it is often difficult to distinguish between linear and curved plots of conversion against time even up to a 20% conversion on the data presented, which is often scanty.…”

Section: Commentarymentioning

confidence: 99%

Absolute propagation constants in vinyl polymerization

Bywater

1999

J. Polym. Sci. A Polym. Chem.

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“…In the gas phase, the attachment of positive ions with thermal energy to an olefin is known to take place with sufficient reaction rates 13 and the situation may be similar also in liquid system when solvation of ion is disregarded. In the radiation-induced polymerization of bulk isobutylene, 14 EP was. found to be 2 kcal mol-t, which showed a fair coincidence with the value in styrene.…”

Section: Discussionmentioning

confidence: 99%