Synthesis, characterization, migration studies and combustion catalytic performances of energetic ionic binuclear ferrocene compounds

The concept of energetic ionic compounds was introduced to retard migration problems encountered in ferrocene-based burning rate catalysts. Fourteen novel compounds, N,N′-bis[(ferrocenylmethyldimethyl)]-1,n-alkylenediammonium (alkylene chain length n = 3–6, 8–10) dinitrate and dipicrate, were synthesized and characterized by NMR, FT-IR, UV–vis spectroscopy, etc. Their thermal stability was determined by TG-DSC technique and found that most of them are thermally stable up to 160 °C. The cyclic voltammetry analysis revealed that the ionic compounds each shows a redox wave for ferrocenyl moiety and the non-conjugated alkylene spacers exert almost no influence on their redox properties. Migration tests showed that their migration tendency is much slower than that of extensively used 2,2-bis(ethylferrocenyl)propane (Catocene) and increases with the extention of alkylene chain length in the cations. Their catalytic performances for thermal decomposition of ammonium perchlorate (AP), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and 1,2,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) were evaluated by DSC method. The ionic compounds presented highly combustion catalytic activity in thermal degradation of AP and RDX. The best catalytic activity in thermodecomposition of AP was obtained with N,N-bis(ferrocenylmethyldimethyl)1,3-propylene diammonium dinitrate, 1. The catalytic activity of 1 is better than that of Catocene and 1 could be used as an alternative to Catocene in hydroxyl-terminated polybutadiene/ammonium perchlorate (HTPB/AP) composite propellants.