Termination usually will not occur in the absence of impurities. The coupling and disproportionation terminations for free radical polymerizations are not possible with anionic polymerizations due to coulombic repulsion of two negatively charged species. Termination involves a proton transfer from another species such as from solvent, monomer, polymer, water etc. But, there is no inherent termination steps in highly pure system. Non terminated polymeric species are referred to as "living" polymers.