The novel energetic triblock copolymer of polypropylene glycol-glycidyl azide polymerpolypropylene glycol (PPG-GAP-PPG) (M_n = 1639 g.mol^-1) was synthesized and optimized by cationic ringopening polymerization of propylene oxide using low-molecular-weight glycidyl azide polymer (GAP) (M_n =1127 g.mol^-1) as the initiator and boron trifluoride etherate (BF₃OEt₂) as the catalyst. This research reveals a new method for polymerization of PPG at room temperature and atmospheric pressure. The synthesized GAP and triblock copolymer were characterized by fourier-transform infrared (FT-IR), gel permeation chromatography (GPC) and nuclear magnetic resonance spectroscopy (¹H and ¹³C NMR). Optimization of temperature and amount of catalyst for the synthesis of PPG-GAP-PPG were also performed. The effect of the temperature and the amount of catalyst on the percentage yield of the reaction and the molecular weight of the triblock copolymer of PPG-GAP-PPG was studied. The optimized temperature and catalyst amount for thesynthesis of triblock copolymer of PPG-GAP-PPG were 10–15^°C and 1% w/w respectively. The thermal stability of the triblock copolymer PPG-GAP-PPG was studied by differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques. The DSC result showed that the glass transition temperature (Tg) ofthe triblock copolymer (Tg = -63^°C) is lower than the neat low molecular weight GAP (Tg = –45^°C). Also,the differential thermogravimetry (DTG) result indicated that this triblock copolymer is more stable than the GAP.