A GAP Replacement, Part 2: Preparation of Poly(3-azidooxetane) via Azidation of Poly(3-tosyloxyoxetane) and Poly(3-mesyloxyoxetane)

Abstract

Despite the variety of energetic polyoxetane binders, the oxirane-based glycidyl azide polymer (GAP) has largely succeeded in the market due to its advantageous properties. Nevertheless, it suffers from various drawbacks such as non-uniform chain termination, possible chlorine content (flame retardant), and toxic epichlorohydrin required for its synthesis. These problems can be bypassed using the structurally related poly­(3-azidooxetane). Unfortunately, it is only accessible in moderate yield by polymerization of 3-azidooxetane. Herein, we describe its synthesis by polymer-analogous transformation using the new polymers poly­(3-tosyloxyoxetane) and poly­(3-mesyloxyoxetane) as precursors. This results in a significantly increased yield and improved safety as handling of the very sensitive 3-azidooxetane is avoided. The aforementioned prepolymers were prepared using boron trifluoride etherate as well as triisobutylaluminum as catalysts. The latter provides polymers of particularly high molecular weight, and the corresponding poly­(3-azidooxetane) species was obtained and studied for the first time. In order to shed light on the applicability of poly­(3-azidooxetane) as a GAP substitute, it was thoroughly studied with regard to thermal behavior, energetic performance (EXPLO5), plasticizer compatibility, and curing. Moreover, the aquatic toxicity of all involved monomers was analyzed and compared to epichlorohydrin. Here, poly­(3-azidooxetane) turned out as a fully adequate, if not more environmentally benign, substitute.

New 5-Aminotetrazole-Based Energetic Polymers: Synthesis, Structure and Properties

“…That said, despite having positive characteristics, GAP is not free of drawbacks that hinder or restrict its practical use in energy-rich materials [ 16 , 17 , 18 ]. To overcome the existing drawbacks, different authors are conducting research on modifying the structural arrangement of the azido polymer in order to create novel GAP-based energetic polymers with improved energetic and performance characteristics [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ].…”

Synthesis of heterocyclic (triazole, furoxan, furazan) fused pyridazine di-N-oxides via hypervalent iodine oxidation

“…Considering that the azide group is a commonly used explosophoric group for constructing energetic compounds, 16 the hydroximoylamine 6 was converted to the corresponding hydroximoylazide 15 using a literature procedure. 13 The cyclization oxidation reaction of compound 15 with PIDA gives 4-(azido(hydroxyimino)methyl)-3-cyano-1,2,5-oxadiazole 2-oxide 16 as the product, and the structure was confirmed by X-ray diffraction (CCDC no.…”