Strained Carbocycle Based Hypergolic Ionic Fuels with the Improved Energy Capacity

Different from the previous nitrogenous groups, we present a new strategy of improving the ionic liquids (ILs) energy capacity by introducing the strained carbocycles. The ILs with three- and/or four-member carbocycles were prepared, and their physicochemical properties as rocket fuels were studied. The ignition tests show that all of these ILs have the expected hypergolic reactivity with the oxidizer (white fuming HNO3). In virtue of the strained cyclopropane and cyclobutane substituents, the resulting hypergolic ILs possess better energy properties (heats of formation 238.9-478.9 kJ mol-1; specific impulses 313.0-315.7 s) and densities (1.03-1.15 g cm-3) than the corresponding ILs with n-alkyl substituents. This strategy of introducing strained ring groups into hypergolic ILs gives a new approach to improve energy properties of hypergolic ILs