New epoxide initiators for the controlled synthesis of functionalized polyisobutylenes

The mechanism of initiation was investigated in isobutylene OB) polymerizat ions initiated by epoxidized alpha -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 PIE. Mode l studies conducted with MSE/TiCl4 and diisobutylene lead to ring closure y ielding a substituted furanyl structure. Real-time fiber-optic refractive i ndex monitoring was used to follow the initiation with the TMPO/TiCl4 syste m. It was found that the cleavage of TMPO proceeds simultaneously by S(N)1 and S(N)2 mechanisms as proposed. The carbocation forming by the S(N)1 rout e is proposed to initiate the polymerization of IB, but it was shown that e xcess TiCl4 relative to TMPO was necessary for propagation. Isomerization a nd polyether formation by the S(N)2 pathway lead to side reactions, reducin g the initiating efficiency.