Ionic liquids as hypergolic fuels

Currently, the ionic liquids (IL) is gaining attention as energetic materials for propellant applications. It is desirable to achieve ignition by means of a hypergolic reaction. Hydrazine and its methylated derivatives are still the state-of-the-art fuels for bipropellant, however, they are carcinogenic vapor toxins. For these reasons, hydrazine has been replaced by ILs, which are regarded as paragons of environmental friendliness, green chemistry, and low vapor toxicity. However, in the first ignition tests carried out with ILs containing fuel-rich azide anions did not disclose any hypergolic properties. Thus, other fuel-rich anions have been investigated, especially the dicyanamide anion. As a result of the investigation, the structure analysis revealed an extensive hydrogen-bond network involving the dicyanamide anion. With the discovery of these ILs hypergols, it is expected that it can now be fine-tuned for energy content, performance, and desirable physical properties and could replace state-of-the-art, highly toxic hydrazine and its derivatives.