Desitgn And Synthesis Of Polycyclic Hvpergolic Ammonium Ionic Liquids

Propellants are the core of power for aerospacecrafts.The current hydrazine-based fues are highly volatile and toxic,it is urgent to develop the green alternatives.Ionic liquids(ILs)with low vapor pressure,low toxicity,high stability,and some with hypergolicity,have the potential as novel fuels of propellants.However,densities of hperpolic ILs need to be further improved so as to yielding the higher propellant loading and specific impulse values.Herein,the new high-density ILs were designed and synthesized by forming rings and adding dense atoms.The contents are as follows:1-Azonia-bicyclo[2,2,2]octane-based hypergolic ILs were designed and prepared.The results show decomposition temperatures 230-322?,densities 1.06-1.27 g cm-3,heats of formation 7.8-431.1 kJ mol-1,specific impulses 261.3.5-265.2 s and ignition delay times 14-186 ms for the ILs.As to 1-methyl-l-azonia-bicyclo[2,2,2]octane dicyanamide,it possesses the higher density(1.20 g cm-3)than the corresponding monocyclic isomer(1-methyl-1-allylpyrrolium dicyandiamide,1.05 g cm-3).Among these ILs,1-propargyl-1-azo-bicyclo[2,2,2]octane dicyanamide exhibits the best comprehensive properties such as density 1.19 g cm-3,specific impulse 265.2 s,heat of formation 431.1 kJ mol-1 and ignition delay time 14 ms.1,4-Diazo-bicyclo[2,2,2]octane-based hypergolic ILs were designed and prepared.The results show that decomposition temperatures 200-282?,densities 1.10-1.31 g cm-3,heats of formation 113.9-537.5 kJ mol-1,specific impulses 260.5-266.2 s and ignition delay times is 20-1053 ms.1,4-Diazo-bicyclo[2,2,2]octane-based ILs possess lower thermal stability and higher density than the corresponding 1-azonia-bicyclo[2,2,2]octane-based ILs.As to 1-propargyl-1,4-diazo-bicyclo[2,2,2]octane dicyanamide,it exhibits the higher density(1.25 g cm-3)that the corresponding monocyclic isome(N-vinyl-N-propylimidazolium dicyanamide,1.07 g cm-3).5,7-Dimethyl-1,3-diazabendane-based hypergolic ILs were designed and prepared.The results show that decomposition temperatures 157-305?,densities 1.18-1.26 g cm-3,heats of formation 11.9-140.9 kJ mol-1 and specific impulses 257.8-263.8 s.As to the IL with the substitute of propargyl,it is hyperglic with white fuming nitric acid.In short,1-azonia-bicyclo[2,2,2]octane,1,4-diazo-bicyclo[2,2,2]octane,and 5,7-dimethyl-1,3-diazabendane-based ILs were obtained with the idea of density improvement.The resulting structures,phase transition temperatures,thermal stabilities,hypergolicity and specific impulse of ILs were measured(or calculated),and fully dicussed.It proves that the three series of ILs have the relatively high densities up to 1.31 g cm-3,which provides the data support and scientific basis for the development of high-density hypergolic ILs.