Abstract: A process for the anionic polymerization or copolymerization of olefinic monomers, dienic monomers, vinyl monomers and heterocyclic monomers is described which comprises reacting at least one monomer which is an olefinic monomer, a vinyl monomer or an heterocyclic monomer with a catalyst capable of inducing anionic polymerization and an aprotic macroheterocyclic cryptant, said at least one monomer being the only medium for the reaction.The macroheterocyclic complexing agent has general formula ##STR1## in which: R.sub.1 is hydrogen, a hydrocarbon radical or alkoxycarbonyl, or the two R.sub.1 together can form a group of the general formula: ##STR2## in which A is a hydrocarbon radical,D is oxygen, sulfur, or a hydrocarbon radical, with the proviso that at leat two of the D groups are oxygen or sulfur and that if R.sub.1 is hydrogen, a hydrocarbon radical or alkoxycarbonyl, one of these two D groups is oxygen or sulfur and the other is oxygen, andn and p are integers from 1 to 3 and m is 2 or 3.

Abstract: A novel process for polymerization or copolymerization of monomers is described, according to which the reaction is carried out in the presence of an anionic initiator and a macroheterocyclic complexing agent of formula ##STR1## in which: EACH R.sub.1 is a hydrogen atom, a hydrocarbon group or an alkoxycarbonyl group, or the two R.sub.1 together can form a group of the general formula: ##STR2## THAT IS TO SAY FORMING A THIRD BRIDGE BETWEEN THE TWO NITROGEN ATOMS IN THE MOLECULE, A is a hydrocarbon group,D is an oxygen or sulfur atom or a hydrocarbon group, with the proviso that at least two of the groups D are oxygen or sulfur atoms and that, if each R.sub.1 is hydrogen, a hydrocarbon group or an alkoxycarbonyl group, one of these two groups D is oxygen or sulfur and the other is oxygen,n and p are integers ranging from 1 to 3, andm is 2 or 3.