Abstract
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.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
