A theoretical study of the cationic dimerization and polymerization of isobutene
Uppsala University1997 (English)In: Journal of Molecular Structure: THEOCHEM, ISSN 0166-1280, Vol. 392, 111-124 p.Article in journal (Refereed) Published
The initial steps in the radiation-induced polymerization of isobutene have been studied by quantum chemical ab initio and semiempirical calculations. The addition of an isobutene cation to a neutral isobutene molecule to form a dimer radical cation is found to be a strongly exothermic reaction, by 29-32 kcal mol(-1) depending on the computational method. A 17 kcal mol(-1) barrier towards a one-hydrogen-shift isomerization reaction, yielding a 2,5-dimethyl-2-hexene radical cation, is obtained at the PMP2/6-31G(d, p) level, which is significantly higher than the value of 6 kcal mol(-1) obtained before for the corresponding isomerization of the ethene dimer radical cation. The further steps of the polymerization of isobutene are investigated in terms of addition reactions between a neutral isobutene moiety and the addition complex formed in the step before. The positive charge and the radical centres are found to be located in opposite ends of each of the radical cationic intermediate complexes, the positive charge centre being energetically the most favourable site of attachment. The overall reaction is thermodynamically favourable and has a high spatial selectivity. The polymer chain has a high structural symmetry and no cross-linking.
Place, publisher, year, edition, pages
1997. Vol. 392, 111-124 p.
isobutene radical cation, dimerization, polymerization, ELECTRON-SPIN-RESONANCE, GAS-PHASE, VANDERWAALS CLUSTERS, 1-BUTENE, ENERGIES
IdentifiersURN: urn:nbn:se:uu:diva-150602DOI: 10.1016/S0166-1280(97)90385-7ISI: A1997XD29900012OAI: oai:DiVA.org:uu-150602DiVA: diva2:407916