Facile Synthesis and Proposed Mechanism of α,ω‐Oxetanyl-Telechelic Poly(3-nitratomethyl-3-methyl oxetane) by an S_N2(i) Nitrato Displacement Method in Basic Media

Abstract

The synthesis of a novel, heterocyclic-telechelic polymer, -oxetanyl-telechelic poly(3-nitratomethyl-3-methyl oxetane), is described. Infra-red spectroscopy (IR), gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy have been used to confirm the successful synthesis, demonstrating the presence of the telechelic-oxetanyl moieties. Synthesis of the terminal functionalities has been achieved via displacement of nitrato groups, in a manner similar to that employed with other leaving groups such as azido, bromo and nitro, initiated by nucleophiles. In the present case, displacement occurs on the ends of a nitratofunctionalised polymer driven by the formation of sodium nitrate, which is supported by the polar aprotic solvent, N,N-dimethyl formamide. The formation of an alkoxide at the polymer chain ends is favoured and allows internal backbiting to the nearest carbon bearing the nitrato group, intrinsically in an SN1 reaction, leading to oxetanyl functionalisation. The telechelic-oxetanyl moieties have the potential to be cross-linked by chemical (e.g. acidic), or radiative (e.g. U.V.) curing methods without the use of high temperatures, usually below 100 o C. This type of material was designed for future use as a contraband simulant, whereby it would form the predominant constituent of elastomeric composites comprising rubbery polymer with small quantities of solids, typically crystals of contraband substances, such as explosives or narcotics. This method also provides an alternative approach to ringclosure and synthesis of heterocycles.

Thermal and Rheological Properties of PGN, PNIMMO and P(GN/NIMMO) Synthesized via Mesylate Precursors

“…The heat of explosion of PGN was calculated as 2661 kJ/kg, which was higher than that of PNIMMO (818 kJ/kg) and glycidyl azide polymer (2500 kJ/kg) [1]. PNIMMO is a promising energetic binder for insensitive munitions and has been investigated [1,[3][4][5].…”

“…In the 1 H NMR spectra of PGN, the signals at approximately 3.36-4.06 ppm were ascribed to the methylene and methine protons, and the peaks at about 4.37-4.64 ppm belong to the methylene 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 protons of the ÀCH 2 ONO 2 [6,16]. In the 1 H NMR spectra of PNIMMO, the single peak at 1.00 corresponded to the methyl protons, the multi-peaks at about 3.23-3.30 ppm were ascribed to the methylene protons, and the peaks at about 4.39 ppm belong to the methylene protons of the -CH 2 ONO 2 [3,17]. The 1 H NMR spectra of P(GN/NIMMO) was about the combination of PGN and PNIMMO.…”