solution was stirred under nitrogen for 4 hours during which triethylamine hydrochloride precipitated in a gelatinous form and the solution became viscous the solution was then filtered and washed with dilute hydrochloric acid 2 100 ml followed by water 3 u00d7 200 ml the solution was then poured into methanol with vigorous stirring and a white fibrous polymer the desired product precipitated the isolated polymer was dried in a vacuum oven at 40 u00b0 c for 24 hours molecular weights were determined by gel permeation chromatography based on polystyrene equivalents blends in accordance with the invention were prepared by thoroughly dissolving and mixing in dichloromethane various proportions of structure ii polycarbonate obtained commercially from the toray chemical co japan and having a weight average molecular weight of 135 000 and a number average molecular weight of 23 400 and the polyester of structure i prepared in accordance with preparations 1 3 above solvent casting the various solutions and then drying off the solvent to yield free standing films of the blends each of the blends of examples 1 3 exhibited good amorphousness and transparency good impact resistance better resistance to chemically caused stress cracking than that of the structure ii polycarbonate itself and a single tg determined by differential scanning calorimetry for purposes of comparison control films outside the scope of the invention were prepared as in examples 1 3 except that control a was composed of 100 of the structure ii polycarbonate control b was composed of 100 of the structure i polyester and control c was composed of a 50 50.