New Epoxy Initiators for the Controlled Synthesis of Functionalized Polyisobutylenes
The mechanism of initiation was investigated in isobutylene (IB) polymerizations initiated by epoxidized α-methylstyrene (MSE) and 1,2-epoxy-2,4,4-trimethylpentane (TMPO) in conjunction with TiCl4. The proposed mechanism predicts primary OH head groups and tertiary Cl end groups in the PIB. Model studies conducted with MSE/TiCl4 and diisobutylene lead to ring closure yielding a substituted furanyl structure. Real-time fiber-optic refractive index monitoring was used to follow the initiation with the TMPO/TiCl4 system. It was found that the cleavage of TMPO proceeds simultaneously by SN1 and SN2 mechanisms as proposed. The carbocation forming by the SN1 route is proposed to initiate the polymerization of IB, but it was shown that excess TiCl4 relative to TMPO was necessary for propagation. Isomerization and polyether formation by the SN2 pathway lead to side reactions, reducing the initiating efficiency.
Puskas, Judit and Michel, Armin, "New Epoxy Initiators for the Controlled Synthesis of Functionalized Polyisobutylenes" (2000). Chemical and Biomolecular Engineering Faculty Research. 540.