Chain polymerization Mechanisms.

Polymers represent an essential class of materials, competing with traditional materials such as metals and inorganic materials, thanks to their low density combined with increasingly sophisticated thermomechanical properties, special properties leading to sometimes highly specific applications (functional polymers) and an ability to be recycled, at least in the case of thermoplastics, which is improving year on year. The industry produced 322 million tonnes in 2015, including 58 million tonnes to cover European demand. A few polymers, known as commodity polymers, account for half of production. In addition, the development of new synthesis methods or processes is leading to materials with totally new properties, and therefore applications, from the same monomers.

This article is devoted to the mechanisms of radical and ionic chain polymerizations, with catalytic chain polymerizations covered in [J 1 260] . Chain polymerization processes (polymerization in homogeneous and dispersed media) are covered in [J 5 832] .