Hydroxyacids/esters, polycondensation

Lactones, i.e. esters of hydroxyacids and their dimers, like glycolide and lactide, are two major groups of cyclic esters used in polymerization. These compounds are used on the large scale and polymerized mostly by anionic or coordinative mechanisms. Four, six-, and seven-membered lactones polymerize by both cationic and anionic mechanisms. Polyesters prepared in this way are however only a small fraction of the polyesters prepared by polycondensation. 

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