Azide Polyether with a Highly Flexible Main Chain as Energetic Materials

Abstract

Poly(3-azidemethyl-3-methyl oxetane) (PAMMO) is an azide-containing polymer that has been widely studied, but some problems, such as its complex synthetic route, high preparation costs, and low elongation, restrict its practical applications. Therefore, it is of great significance to design and synthesize an azide polyether that is low in cost, highly flexible, and has a comparable energy level to that of PAMMO. In this paper, we synthesized an azide polyether, poly(2-azidemethyl-1,3-dioxolane) (PADOL), through a simple two-step reaction. The first step was a cationic ring-opening polymerization using 2-chloromethyl-1,3-dioxane (CDOL) as a monomer, and the second step was an azidation reaction. The synthesized PADOL had a controlled molar mass and low dispersity, and the degree of functionality of the terminal hydroxyl group was close to the theoretical value. In addition, 3,3-bisazidemethyl oxetane-2-azidemethyl-1,3-dioxolane random copolymers (PBAMO-ADOLs) were also synthesized using CDOL and 3,3-bischloromethyl oxetane (BCMO) as monomers in the same two-step reaction scheme discussed above. The copolymerization kinetics showed that the reactivity ratios of CDOL and BCMO were similar, and the copolymerization process was close to an ideal copolymerization. When the ADOL content in the PBAMO-ADOL copolymer was up to 27%, the crystallinity of the BAMO chain segment was effectively reduced, and an amorphous azide-containing polymer was obtained. Thanks to the higher oxygen content and short side chain length, PADOL exhibited a lower glass transition temperature and viscosity than PAMMO, and the prepared energetic thermoplastic elastomer (ETPE) had a higher fracture elongation. Moreover, the higher oxygen content in PADOL promoted the decomposition of the polymer backbone, resulting in a higher absolute value of the heat of combustion and lower residual carbon content.

Synthesis and Characterization of Functionalized Polylactides Containing Acetal Units

“…The pendant reactive groups in the polyester chain provide the opportunity for modification in nucleophilic substitution, azide–alkyne cycloaddition click, or thiol–ene click reactions, as shown in Scheme S2a,b. As a proof of concept, the PLA/PCl-DXL copolymers were reacted with sodium azide to replace the halide group with an azide group. , The reaction was performed in DMF or acetonitrile, solvents that are suitable for the S N 2 mechanism. The modification of copolymers was verified in the 13 C NMR spectra because of the overlapping proton signal in the 1 H NMR spectrum.…”

“…As a proof of concept, the PLA/PCl-DXL copolymers were reacted with sodium azide to replace the halide group with an azide group. 41,42 The reaction was performed in DMF or acetonitrile, solvents that are suitable for the S N 2 mechanism. The modification of copolymers was verified in the 13 C NMR spectra because of the overlapping proton signal in the 1 H NMR spectrum.…”

Click Chemistry for Linker-Free BAMO-Based Energetic Sequence-Controlled Copolymers

“…Energetic materials hold significant importance in several domains, such as aerospace, military weaponry, resource exploitation, etc. − As a result, there is a growing trend toward the use of energetic polymer binders, which aim to provide excellent mechanical properties and increase the overall energy level of solid rocket propellants and PBXs. − Generally, the preparation of energetic polymers involves the introduction of energetic groups, which can reduce the flexibility of their bulky volume and high polarity. To overcome this defect, copolymerization is considered a viable method to achieve intramolecular plasticization by modifying the regularity of the backbone structure. , This commonly used method typically improves flexibility by increasing the proportion of soft chains, which can lead to a decrease of energetic groups, thereby lowering energy levels. − …”