1. Historical context

Polyesters are polymers characterized by the presence of ester groups in the backbone of the macromolecule. Within this large family of polymers, the following types are distinguished:

• saturated polyesters, which contain saturated hydrocarbon groups;

• aromatic polyesters, which have an aromatic ring in the main chain;

• unsaturated polyesters, which may contain carbon-carbon double bonds within the chain.

These are very old polymers (for example, polyhydroxyalkanoates (PHA) were discovered in 1926, and the first patent for PET was granted in 1941) and are used in a wide range of industrial sectors (packaging, textiles, formulation, and biomedicine, due to their biocompatibility). They were extensively developed during the 20th century, but...