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 C-13-nuclear magnetic resonance (C-13 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 degrees C to -51 degrees C) than PBAMO (-37 degrees C) and higher thermal decomposition temperatures (233-237 degrees C) than PBAMO (211 degrees 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.