Cationic polymerization of cyclic thioacetals by triethyloxonium tetrafluoroborate

Polymerization of 1-oxa-3-thiacyclopentane with catalytic amounts of triethyloxonium tetrafluoroborate was studied. The initiation reaction was a fast and quantitative formation of ethylsulfonium salt of monomer. The propagation reaction was a slow and quite complex reaction with sulfonium transfer reactions. The reaction mechanism is discussed.