Environmentally benign process for bulk ring opening polymerization of lactones using iron and ruthenium chloride catalysts

FeCl3·6H2O, RuCl3·H2O and FeCl2·4H2O are found to be bulk polymerization catalysts for the ring opening polymerization of ε-caprolactone, δ-valerolactone and β-butyrolactone. These polymerizations can be significantly enhanced by conducting them in the presence of appropriate amounts of different alcohols. The major initiation pathway in the polymerization is found to proceed via the activated monomer mechanism and depending on the nature of the alcohol used, poly(lactones) with different end groups can be synthesized. Such polymerizations constitute an economical process, employing readily available inorganics as catalysts and do not necessitate solvents. The overall system is green and eco friendly. © 2008 Elsevier B.V. All rights reserved.