Polymers of 1-Alkyl-3-vinylimidazolium Energetic Ionic Liquids as Fuel Binders in Propellant Compositions

Abstract. Polymers of 1-alkyl-3-vinylimidazolium perchlorate and nitrate energetic ionic liquid building blocks are used as fuel-binders in propellant compositions. These polymers exhibit extraordinary tuneability of mechanical, energetic, ammonium perchlorate (AP) surface binding, and self-healing properties through side-chain design in the monomers. The vinyl groups on the imidazolium cations provide covalent interconnects for the formation of the polymer backbone, while poorly packing alkyl groups, such as isopropyl, long chain alkyls, and oligo-ethylene glycol groups are found to act as internal plasticizers, enabling control over the mechanical properties, as well as the surface binding to AP crystals, and even self-healing properties of the polymer, as well as of the cured composite product. The advantageous oxygen balance and heats of formation of these energetic ionic liquid monomers enables a reduction of the ratio between the polymer and the heterogeneous oxidizer, without compromising the energetic properties of the resultant propellant. All 1-alkyl-3-vinylimidazolium perchlorate tested to date readily polymerize through a radical mechanism. Appropriately designed monomers may serve as a photoactive resin for high resolution 3D printable propellants.