AbstractThe anionic ring‐opening polymerization may result in a broad variety of homo‐ and copolycarbonates. Upon suitable selection of monomers, polymers with functional groups may be obtained which are eligible to cross‐linking reactions or exert a high degree of hydrophilicity. Copolymers with lactones are readily obtained, provided both polymerization reactions follow the same mechanism; the ring‐opening polymerization of cyclic carbonates is exclusively initiated by alcoholate ions and not by carboxylate anions. Since butyllithium is a suitable Initiator for the ring‐opening anionic polymerization of cyclic carbonates, living vinyl polymers may be used as initiators as well to obtain the respective blockcopolymers. Instead of living vinyl polymers obtained in the conventional manner, using carbanionic Initiators, also living polymers obtained by group transfer polymerization may be used as initiators for the ring‐opening polymerization of cyclic carbonates; the mechanism for the latter polymerization, however, then is rather a non‐metallic anionic one than a group trans