Anionic ring-opening polymerization cyclic ester

There are various systems that fulfill the different conditions, namely thermoplastic PU, anionic ring-opening polymerization of polyamide, entropy driven ring-opening polymerization of cyclic oligo-esters. 

Cationic and anionic polymerizations of heterocyclic monomers provide many examples in which the concurrent formation of cyclics of various sizes is observed during the ring-opening polymerization. As illustrated in Scheme 1, in these systems active species follow three pathways they can react with a functional group of the monomer, of its own polymer chain, or of other chains. When the function / involved belongs to a linear polymer chain, intramolecular chain saambling or intermolecular macrocycle formation takes place, as observed in the cationic polymerization of cyclic ethers, acetals, esters, amides, siloxanes, and so forth. 

It is believed that the controlled cationic ring-opening polymerization proceeds by an activated anionic mechanism as suggested by Penczek [91]. According to his suggestion, the acid activates the cyclic ester and the alcohol subsequently initiates the polymerization. 

---