In this article, we performed dehydration polycondensation of bromosuccinic acid and methylsuccinic acid with 1,4- butanediol at 80 1C to synthesize aliphatic polyesters containing pendent bromo groups without dehydrobromination using scandium trifluoromethanesulfonate (Sc(OTf) 3) as the catalyst. Azidation of the resultant polyesters was carried out readily in N, Ndimethylformamide at room temperature using sodium azide (M-n = 8.3 x 10(3) (M-w/M-n=2.17)). H-1 nuclear magnetic resonance analysis of the product revealed that 65% contained azide functionality, and dehydrobromination occurred in 35% during the azidation process. On the other hand, azidation of poly(butylene bromoadipate-co-butylene methylsuccinate) (poly(BBA-co-BMS)) proceeded successfully under the same conditions to generate poly(butylene azidoadipate-co-butylene methylsuccinate) (poly(BAA-co-BMS)) without dehydrobromination (M-n=10.4 x 10(3) (M-w/M-n=2.71)). We successfully photo-crosslinked the resultant azidopolyester by ultraviolet irradiation and examined it using scanning electron microscope. We also described azidation of polyesters having pendent hydroxyl groups by using the 'DPPA (diphenylphosphoryl azide)-DBU (1,8diazabicyclo[5.4.0] undec-7-ene) substitution strategy' to produce water-soluble polyesters containing pendent azido groups (M-n=7.5 +/- 103 (M-w/M-n=2.25)). These azidopolyesters might be extremely useful not only for their derivatization by simple chemical modification but also for their effective utilization as photolithography material. Polymer Journal (2011) 43, 272-278; doi: 10.1038/pj.2010.135; published online 12 January 2011