Synthesis and characterization of carboxylated PBAMO copolymers as promising prepolymers for energetic binders

Abstract

The carboxylated poly[3,3-bis(3-azidomethyl)oxetane] (PBAMO) copolymers (poly(BAMO-carboxylate)) were synthesized by substitution of poly[3,3-bis(3-chloromethyl)oxetane] (PBCMO) with potassium carboxylate and sodium azide in DMSO. The synthesized compounds were characterized using various analytical techniques, such as Fourier-transform infrared (FT-IR) spectroscopy, inverse-gated decoupling ¹³C-nuclear magnetic resonance (¹³C NMR) spectroscopy, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), calorimetry, friction, and impact sensitivity analysis. These poly(BAMO-carboxylate) compounds have better thermal properties, with lower glass transition temperatures (ranging from −43 °C to −51 °C) than PBAMO (−37 °C) and higher thermal decomposition temperatures (233–237 °C) than PBAMO (211 °C). Moreover, poly(BAMO_0.80-octanoate_0.20) and poly(BAMO_0.78-decanoate_0.22) have higher heats of combustion (5226 and 5665 kJ mol⁻¹, respectively) and negative formation enthalpies (−0.17 and −0.55 kJ g⁻¹, respectively), while PBAMO has lower heat of combustion (3125 kJ mol⁻¹) and positive formation enthalpy (0.06 kJ g⁻¹). The poly(BAMO-carboxylate) compounds have higher values (38–50 J) than that of PBAMO (14 J) in the impact sensitivities. This is a valuable study for improving the properties of PBAMO, which is a high energetic polymeric binder but difficult to handle because of its sensitivity. Therefore, poly(BAMO-carboxylate) could be a good candidate as a prepolymer for designing the energetic polymeric binder.