Special Features of the Polymerization of Heterocyclic Monomers

Objective: The short review summarizes old and more recent findings highlighting special features of polymerizations of heterocyclic monomers, which usually are not observed in processes leading to low molar mass products. These features include: Influence of the initial monomer concentration on its equilibrium concentration, role of monomer in determination of the relative reactivity of “free” ions and ion-pairs in propagation, formation of products composed of linear and cyclic macromolecules, and influence of stereospecificity of each propagation step on microstructure of the final polymer. Discussion: In polymerization of heterocyclic monomers elementary reactions responsible for synthesis of polymers are, in principle, the same as those in “classical” chemistry of heterocyclic small molecules. However, these two classes of processes are distinct, because in the majority of polymerization systems the same heteroorganic groups are present in substrates (monomers) and reaction products (linear polymers). Results: In result, the active polymerization centers react not only with monomers but also with polymers. Moreover, in polymerization processes the monomer always constitutes a significant part of the liquid medium and influences its physicochemical properties. Keywords: Heterocyclic monomers, cyclic ethers, cyclic esters, cyclic siloxanes, ring-opening polymerization, chain transfer, macrocyclization, free ions, ion pairs.