The cationic polymerization of 2-methyl-2oxazoline was carried out at 0 degrees C in acetonitrile using an acid-exchanged montmorillonite as acid solid ecocatalyst (Maghnite-H+). The effect of the amount of catalyst, solvent, and times of polymerization on yield and viscosity of polymer was studied. A typical reaction product (PMOX) was analyzed by infrared and nuclear magnetic resonance spectroscopy as well as by gel-permeation chromatography and MALDI-TOF MS. The polymers presented similar spectrometric results and narrow molecular weight distribution. The poly(N-acetyl)iminoethylene was hydrolyzed in acid medium obtaining a linear poly(ethyleneimine). (c) 2006 Wiley Periodicals, Inc.