Synthesis, characterization, migration and catalytic effects of energetic ionic ferrocene compounds on thermal decomposition of main components of solid propellants

Sixteen new energetic ionic ferrocene compounds, [FcCH2N(CH3)2(CnH2n+1]+X− (Fc = ferrocenyl; X− = nitrate or picrate anion; n = 3–10), were synthesized in high yields and characterized by 1H NMR, 13C NMR, UV–Vis, elementary analysis, TG and DSC methods. All the compounds show high thermal stability. Cyclic voltammetry investigations revealed that the ionic compounds exhibit redox waves for ferrocenyl groups and are considered as irreversible redox systems. Migration studies disclosed that their migration tendency increases with elongation of alkyl chain length in the cations of the compounds, and much slower than that of neutral n-butylferrocene (NBF). The sensitivities tests towards impact and friction revealed that all picrates are sensitive compounds, while the nitrates are less sensitive analogs. Their catalytic performances for thermal degradation of main components of solid propellants such as ammonium perchlorate (AP), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), 1,2,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) and hydroxyl-terminated polybutadiene (HTPB) as well as 1:1 mixture of HTPB and AP, were evaluated by DSC and/or TG techniques. All the ionic compounds can efficiently catalyze the thermal degradation of AP, HTPB and their 1:1 mixture. Compounds 1–8, 11 and 16 exhibit catalytic activity in thermal decomposition of RDX. None of them display distinct catalytic effect on the thermal degradation of HMX. These low-migration ferrocene derivatives may be used as alternatives to NBF in HTPB/AP composite solid propellants.