Ecofriendly synthesis and characterization of carboxylated GAP copolymers.

Carboxylated GAP copolymers (polyGA-carboxylate) compounds (1-7), were synthesized by the simultaneous substitution reaction with PECH, sodium azide, and sodium carboxylate in DMSO. The synthesized compounds (1-7) were characterized by various analysis tools, such as Fourier transform infrared (FT-IR), inverse gated decoupling 13 C-nuclear magnetic resonance ( 13 C NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), calorimetry, and friction and impact sensitivity. These poly(GA-carboxylate) compounds (1-7) have better thermal properties owing to their lower glass transition temperatures, from -48 °C to -55 °C, compared to glycidyl azide polymer (GAP) (-49 °C) and similar first thermal decomposition temperatures (228-230 °C) in comparison to GAP (227 °C), regardless of the introduction of the carboxylate group in GAP. Moreover, poly(GA 0.8 -butyrate 0.2 ) and poly(GA 0.8 -decanoate 0.2 ) have higher heats of combustion (2331 and 2976 kJ mol -1 ) and negative formation enthalpies (-0.75 and -2.02 kJ g -1 ), while GAP has a lower heat of combustion (2029 kJ mol -1 ) and positive formation enthalpy (1.33 kJ g -1 ). Therefore, poly(GA-carboxylate) could be a good candidate for the polymeric binder in solid propellants.