Tandem-action ferrocenyl iodocuprates promoting low temperature hypergolic ignitions of "green" EIL-H(2)O(2)bipropellants

The combination of Energetic Ionic Liquid (EIL) "green" fuels and high test peroxide (>90% H2O2; HTP), as a "green" oxidizer, is a very promising platform for the development of fully "green" bipropellants for space exploration. In this work, two new "tandem-action" promoters - [FcCH(2)N(CH3)(3)(+)](2)[Cu2I42-] (P1) and [FcCH(2)N(CH3)(3)(+)](n)[Cu2I3-](n)(P2) - and two reference "single-action" promoters, [FcCH(2)N(CH3)(3)(+)][H3BCN-] (P3) and [CH3N(CH2CH3)(3)(+)](n)[Cu2I3-](n)(P4), were prepared, comprehensively characterized and evaluated for their ability to significantly shorten the Ignition Delay (ID) times of hypergolic reactions between a series of EILs and H2O2. These promoters exhibited high solubility and long-term chemical stability in a typical EIL fuel - 1-ethyl-3-methylimidazolium dicyanamide (F1). Upon screening the performance of promoter-EIL formulations, the best ID result of 31 ms was observed for the combination of 1-ethyl-3-methylimidazolium cyanoborohydride (F2) fuel and promoterP2(10 wt%), with H2O2(95%), whereas an ID time of 58 ms was observed for theF2/P2formulation with commercially available H2O2(70%), respectively. Remarkably, the latter formulation remained fully homogeneous even at -40 degrees C, and showed an ID time of 66 ms at this temperature with H2O2(95%), indicating the advantages of our approach for the development of novel fully "green" bipropellants.