2. Classification of polymerization reactions

Depending on the kinetic behavior and mechanism of the reaction that leads to the formation of the macromolecular compound, two main types of polymerization reactions are traditionally distinguished:

• step polymerizations, often called polycondensations, in which the formation of the macromolecule results from the reaction between reactive functions carried by the monomer or polymer molecules;

• chain polymerization, in which a single initial active center (ion, radical or organometallic complex) carried by the growing chain acts on the monomer molecules to form a macromolecule.

The former behave like simple balanced reactions between reactive functional groups, while the latter have the characteristics of chain reactions.

Step polymerizations are used...