Abstract: A copolymer having carbonate linkages is produced by copolymerizing an epoxy compound with carbon dioxide in the presence of an isoprene-magnesium complex compound or a reaction mixture of said complex compound with an active hydrogen compound as a catalyst. The catalyst has a much improved polymerization activity when treated with carbon dioxide in advance.

Abstract: A catalyst composition and a process for preparing same comprising the reaction product of (a) an organo-metallic compound having the general formula R'nM, wherein n is an integer, at least one R' is an alkyl group, an alicyclic group, or halogen, hydroxy or alkoxy derivatives thereof, or hydrogen, the remaining R' groups are alkyl groups, alicyclic groups, alkaryl groups, aralkyl groups, aryl groups, or halogen, hydroxy or alkoxy derivatives thereof, and M is a metal of Group II or Group III of the periodic Table, (b) a co-catalyst component which is sulfur or a compound containing active hydrogen atoms, and (c) carbon dioxide. The catalyst composition is used in preparing copolymers of epoxy compounds with carbon dioxide.