Synthesis and Characterization of Azide Functionalized Copolymers and Energetic Thermoplastic Elastomers

Abstract

The energetic polymeric binders of solid propellants such as glycidyl azide polymer (GAP), poly[3,3-bis(3-azidomethyl)oxetane] (PBAMO) have some drawbacks due to presence of bulky and polar azide groups, while it has an excellent performance of propellants in terms of energy output. To improve the mechanical properties of GAP and PBAMO, GAP and PBAMO copolymers have been synthesized. These GAP and PBAMO copolymers have better mechanical properties than GAP and PBAMO owing to the introduction of different monomers or polymers. Our studies have focused on the improvement of the mechanical properties of GAP and PBAMO, and the completion of substitution reactions so that the extra sodium azide was not left in liquid wastes, thus ensuring eco-friendly reactions. Firstly, GAP copolymers based on 1,2,3-triazole (poly(GA-triazole) (2, 3)) were synthesized by the reaction with GAP and alkyl propargyl ether in DMSO. Secondly, PBAMO copolymers based on carboxylate (poly(BAMO-carboxylate) (5-7)) were synthesized by the two-step substitution reaction with PBCMO, sodium azide, and potassium carboxylate in DMSO. Finally, the ETPE based on GAP (GAP-ETPE (10)) and ETPE based on poly(GA-carboxylate) (poly(GA-carboxylate)-ETPE (11, 12)) were synthesized by the reaction with GAP or poly(GA-carboxylate) (8, 9), dibutyltin dilaurate (DBTDL), isophorone diisocyanate (IPDI), and 1,4-butanediol (1,4-BD) in ethyl acetate. The synthesized GAP, poly(GA-triazole) (2, 3), PBAMO, poly(BAMO-carboxylate) (5-7), GAP-ETPE and poly(GA-carboxylate)-ETPE (10-12) were characterized by various analysis tools such as fourier transform infrared (FT-IR), inverse gated decoupling 13C-nuclear magnetic resonance (13C NMR), 1H-nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), universal testing machine (UTM), calorimetry, friction, and impact sensitivity.