synopsisThe polymerization of four unsaturated episulfides, vinylthiirane, endo-2,3-thioepoxynorbornene, cyclooctadiene-1,EZ-monoepisulfide and allyloxymethylthiirane can be affected by various ionic catalysts, BuLi, ZnEtsHz0, BF3.Et20, etc. In case of conjugated functional groups, some catalysts afford isomeric structures resulting from participation of both the olefmic and the episulfide group; the latter can also be opened s e p arately, but even for radical initiation of vinylthiirane no l12-structure of a pure vinyl polymer was obtained. A rearrangement of 1,3-to 1,Bpolymer has been observed in some cmes by post treatment.