We succeeded in developing the acyl chloride-facilitated condensation polymerization method for the synthesis of new poly(anhydride-ester)s with aromatic side groups, which cannot be polymerized by the classic melt condensation polymerization method. Using chlorinated and acylated carboxylic acids as the intermediates, the polymerization was carried out at low temperatures of 120 or 135 degrees C to yield pure poly(anhydride-ester)s of molecular weights as high as 1.55 X 10(5) with minimal side-reactions. A homogeneous route of preparation was developed and optimized, using butyric anhydride as the acylating reagent and oxalyl chloride as the chlorinating reagent. A comparison of the mechanisms of the classic method and the new method indicates that the effects of transacylation-cyclization and oligomer formation-were greatly reduced due to the high reactivity of carboxylic acid chloride and the steric effect of bulky acyl groups. (c) 2007 Wiley Periodicals, Inc.