Polymerization of Aromatic Aldehydes. V. Cationic Cyclopolymerization of o-Vinylbenzaldehyde

Polymerization of o-vinylbenzaldehyde was carried out at 0°C with BF3OEt2 catalyst. The polymers obtained as white powders were soluble in common organic solvents, and were not cleaved by treatment with dilute hydrochloric acid. The degree of polymerization was 20–30. The polymer contained approximately 20% of the pendent vinyl group and 5% of the pendent aldehyde group. The rest of the monomer unit was presumably the cyclized unit. On the basis of these structural data, a cationic propagation scheme of o-VBA was proposed, in which the neighboring aldehyde group reacted overwhelmingly with the growing cation to form a cyclic unit and the intramolecular cyclization of the neighboring vinyl group with the cation was competitive with the intermolecular propagation. This scheme was consistent with that expected from the cyclopolymerization schemes of o-divinylbenzene and o-phthalaldehyde.