In this article, the synthesis and characterization of cyclic polyesters of poly(oxyepichlorhydrin oxymaloyl) from a ring-chain reaction induced by "Maghnite," an acid-exchanged montmorillonite as acid solid ecocatalyst (Mag-H+), is described. Maghmite is already used as catalyst for polymerization of many vinylic and heterocyclic monomers [Belbachir, U.S. Pat. 066969.0101 (2001)]. The reactions were monitored by gel permeation chromatography and H-1-NMR spectroscopy and the existence of cyclic species was proven. The effect of the amount of catalyst on yield and molecular weight of polymer was studied. (c) 2006 Wiley Periodicals, Inc.