Radical Cyclopolymerization of Divinyl Ether. The Microstructure of the Polymer and the Cyclopolymerization Mechanism

Radical polymerization (AIBN initiator) of divinyl ether yielded partially cyclized, soluble polymers. The pendent vinyloxy group could be completely removed by treating the polymers with 2% hydrochloric acid in methanol. Based on ¹³C-NMR spectra of these polymers, the original polymer was concluded to contain a five-membered monocyclic unit with the pendent vinyloxy group and a bicyclic unit (dioxobicyclo[3.3.0]octane system) in the 1:1 ratio. The carbon chemical shifts expected for all the possible stereoisomers of these structural units were estimated using a number of model compounds. Apparently a single stereoisomer was formed for both the monocyclic unit (trans ring closure) and the bicyclic unit (with the trans junction). Finally, the steric course of the cyclopolymerization was compared with those of the related systems.