Journal of Energetic Materials

polyester polyol can be used in high energy propellant as a binder.In this research, polyazido polyester was synthesized from direct polycondensation reaction between adipic acid and 2,2-bis(bromomethyl)-1,3-propanediol. Then, azidation of poly bromoester afford polyazidoester as an energetic polyester. polyazidoester have identified and characterized by FTIR,HNMR,GPC,DSC and elemental analysis methods. The result of GPC showed that the molecular weight of synthesized polyester is about 5900 Dalton..The result of TGA/DSC showed that the thermal decomposition of polyazidoester involved three steps. it is found that the first and second steps were mainly corresponding to the thermal decomposition of azidomethyl groups (CH2N3) to methylnitrene group, and the third step was mostly corresponding to the thermal decomposition of the remaining polyester backbone. Also for interpreting the dropping of glass transition temperature of azidoester ,the crankshaft motion of repeating unit was modeled by grid search about two -O*-CH2-C(CH2Br)2-CH2OH dihedral angles using semiempirical calculation. The results have shown that the activation energy of crankshaft motion of the polyester segments have reduced by substitution of brome with azide which caused the Tg of polyazidoester is lower incomparison to polybromoester .