Poly(adipic anhydride) (PAA) was prepared by the ring-opening polymerization of adipic anhydride (AA) initiated by potassium poly(ethylene glycol)ate. The effects of various factors, such as the amount of initiator, concentration of the monomer, reaction time and temperature, and polarity of the solvent on the polymerization were investigated. The crude polymerized product was a mixture of PAA homopolymer and poly(ethylene glycol)-poly(adipic anhydride) block copolymer, as confirmed by H-1-NMR and gel permeation chromatography. Chain-transfer reactions occurred intensively for the AA polymerization in both the nonpolar solvent toluene and the polar solvents CHCI3 and tetrahydrofuran, which predominantly determined the molecular weight and the monomer conversion for the polymerized product. The lower monomer conversion in toluene was ascribed to a lower livingness for the initiator in the nonpolar solvent when compared with other two, polar solvents. (C) 2003 Wiley Periodicals, Inc.