Magnesium bromide (MgBr2) as a catalyst for living cationic polymerization and ring-expansion cationic polymerization

Magnesium bromide (MgBr2) was found to be an effective catalyst for the ring-expansion cationic polymerizations of isobutyl vinyl ether (IBVE) initiated by a cyclic hemiacetal ester (HAE) bond-based initiator leading to the syntheses of cyclic poly(IBVE)s. Crucial to the achievement is the choice of the quencher (e.g., DMF or DMSO) instead of methanol as well as the realization of living cationic polymerization with an acyclic HAE-based initiator under magnesium catalysis. The advantage of MgBr2 over a conventional catalyst (i.e., SnBr4) is that several types of cyclic molecules are available as initiators, including a methacrylate type vinylidene group-embedded cyclic compound. The reactive group-carrying initiator allowed the pin-point incorporation of a polar group (e.g., glycerol) into the resultant cyclic polymer via a thiol-Michael addition reaction while retaining the cyclic topology.

Automated summary

Magnesium bromide was found to be an effective catalyst for ring-expansion cationic polymerizations of isobutyl vinyl ether, resulting in the synthesis of cyclic poly(IBVE)s. The use of a quencher instead of methanol, along with the realization of living cationic polymerization under magnesium catalysis, were crucial for this achievement. The advantage of MgBr2 over conventional catalysts is its ability to use various types of cyclic molecules as initiators and facilitate precise incorporation of polar groups into the resultant cyclic polymers.