Design And Synthesis Of N-Three/Four-membered Cyclic Imidazolium Hypergolic Ionic Liquids

As the main source of power for spacecraft,propellant performance directly affects the launch effect and plays a pivotal role in the development of aerospace industry.Compared with traditional propellants,hypergolic ionic liquids have the advantages of low toxicity,good stability,low vapor pressure,and environmental protection,and have broad development prospects.However,the energy of hypergolic ionic liquids currently studied is generally low and needs to be further improved.In view of this,this paper proposes to design and synthesize a series of high-energy spontaneous ionic liquids with single/double tension ring structure based on the intramolecular tension energy.The specific research contents are as follows:(1)Designed and synthesized 12 high-energy N-single tension cyclic imidazolium hypergolic ionic liquids.The results show that the tension ring spontaneous combustion ionic liquid has a higher energy,the enthalpy of formation is 0.8?1.9 k J·g^-1 and the specific impulse is 157.4?171.9 s,of which 1-methylcyclopropyl-3-methyl Imidazolium dicyandiamide The energy of salt is the highest,the enthalpy of formation reaches 1.9 k J·g^-1,and the specific impulse reaches 171.9 s.The Guassian calculation results show that the enthalpy of formation of 1-methylcyclopropyl-3-methyl imidazolium dicyanamide salt is 58%higher than that of tension-free ring structure 1-butyl-3-methyl imidazolium dicyanamide salt.The addition of the tension ring structure can significantly increase the energy of the hypergolic ionic liquids.(2)Designed and synthesized 5 kinds of N-double tension cyclic imidazolium pyrophoric ionic liquids,realizing the further improvement of the energy of pyrophoric ionic liquids.The results show that the enthalpy of formation of the five pyrophoric ionic liquids is 1.5?2.0 k J·g^-1,and the specific impulse is 166.6?173.9 s.The energy is significantly higher than that of the single tension ring spontaneous ionic liquid.Among them,the highest enthalpy of formation of 1,3-dimethylcyclopropylimidazolium dicyanamide salt is 2.0 k J·g^-1,and the specific impulse reaches 173.9 s.The calculation results show that under the same anion,the1,3-dimethylcyclopropyl imidazolium ionic liquid has a higher enthalpy of formation,which is 64%higher than the enthalpy of formation of 1,3-dibutyl imidazolium ionic liquids with no tension ring structure.In summary,two types of N-single tension cyclic imidazolium hypergolic ionic liquids and N-double tension cyclic imidazolium hypergolic ionic liquids have been synthesized in this paper.The structure,glass transition temperature,density,spontaneous ignitability,viscosity,enthalpy of formation and specific impulse of the obtained hypergolic ionic liquids were measured,which provided important experimental support for high-energy ionic liquids as new green propellants.