Synthesis, Structure, Mobility Of Novel Ferrocene Ionic Compounds And Their Catalysis For Thermal Decomposition Of Energetic Compounds

Ferrocene and its derivatives are capable of modifying the combustion of the hydroxyl-terminated polybutadiene(HTPB)/ammonium perchlorate(AP)composite solid propellants as burning rate(BR)catalysts.However,these simple ferrocenyl compounds,due to their low molecular weights,show obvious migration tendency and volatilization problems during curing process and longtime storage of the propellants,which could cause uneven combustion and great damage to the propellants,and even affect personal safety.In addition,mixtures of the volatilized neutral ferrocene BR catalysts and the ultra-fine AP are sensitive to electrostatic discharge.To solve theseproblems,we designed and synthesized a series of mono-and dinuclear ferrocenylenergetic ionic compounds by increasing the number of carbon atoms on the side chains of the ferrocenyl molecules,or introducing polar function groups containing nitrogen or oxygen atoms into the ferrocenyl molecules,to retard or even prevent ferrocene-based BR catalysts from migration and volatilization.The contents of this research works is asfollows:48 ferrocenyl ionic compounds composed of mono-or dinuclearferrocene-functionalized quaternary ammonium cations paired with 1,1,2,3,3-pentacy anopropenide(PCP),1,1,2,5,6,6-hexacyano-3,4-diazahexadienediide(HCP)and styphnic(TNR)anions were prepared.The synthetic processes are friendly to environment and easy to be achieved.The new compounds were characterized by melting point determination,1H NMR,13C NMR,FT-IR,UV/Vis,elemental analysis.Some compounds were characterized with single crystal X-ray diffraction.Electrochemical properties,thermal stability,migration,volatility and catalytic activities to the main components of the solid propellant of the new compounds were then evaluated.The test results are summarized as follows:The electrochemical behavior of all compounds in DMSO solution were investigated by cyclic voltammetry.The oxidation potentials of the compounds are higher by 200-300 mV than those of NBF,TBF and Catocene,indicating that the new ferrocenyl salts cannot be easily oxidized in DMSO on comparison with NBF,TBF,and Catocene.The ?Ep of the Fc/Fc+ couple in compounds 1-8 is less than 80 mV,and the ratio of oxidation and reduction peak currents between 1.0 and 1.5,they can therefore be regarded as reversible redox systems.Other compounds are irreversible redox systems.Thermal stability is a key property for components in solid propellant formula and therefore thermal behaviors of compounds 1-48 are investigated by TG and DSC.From the TG and DSC curves,it can be seen that most compounds have good thermal stability.Under the same test condition,the decomposition temperature peaks of dinuclear ferrocene compounds are generally higher than those of mono-ferrocene compounds.It is also noted that the compounds containing PCP anions have significant higher thermal stability than the compounds with HCP anions,due to the inherent lower thermal stability of the HCP anion.For the similar structure compounds,their different length of alkyl chain have little influence on thermal stability.Anti-migration behavior of some selected compounds were investigated in comparison with Catocene.The migration percentages of the compounds in the cross-linked HTPB against their migration distance and aging time at 70 ? were measured.The results implied that all of the compounds have much lower migration rates on comparison with that of Catocene.The anions exert strong effect on the migration tendency of the ionic compounds.The migration tendency order of the new compounds with different anions is TNR<HCP<PCP(here the abbreviations of the anions were used to represent the compounds).Volatility of compounds 33-48 was evaluated by TG technique at a consistent temperature.According to the TG curves of 33,41,44,47 and Catocene measured at 70 ? for 24 h,the new compounds have no significant weight loss,their weight losses is between 0.1%and 4.3%,less than that of Catocene(4.4%).Compared with mono-ferrocenyl compounds,the dinuclear ferrocenyl compounds have higher residual mass.AP,RDX,and HMX are extensively used as core components in solid propellants.Different mass percents of selected new compounds were mixed with AP,RDX,or HMX to determine the optimized addition percentages in them through analysis the released heats of the mixtures.The experimental results indicated that all the ionic ferrocenyl compounds can obviously alter the AP thermal decomposition.The high temperature decomposition(HTD)stage of AP move left to a great extent and the degradation temperature span was narrowed significantly from 170 ? to about 100 ?.The released heat of AP with the addition of the ionic compounds 45-47 is in the range of-1514.5?-1727.7 J·g-1,much higher than that of the mixtures of AP and Catocene.Most of the compounds can advance the decomposition temperature peak of RDX and increase its released heat.Of which,the mixture of 2 wt.%44 with RDX can release-1599.2 J·g-1,more than twice of the released heat of RDX.A few compounds can advance the decomposition temperature peak of HMX,but the released heats are lower than that of HMX,implying that no obvious effect on the thermal decomposition of HMX was exerted by the new compounds.In summary,the synthesized novel compounds show highly combustion catalytic properties for main components of solid propellants.The new compounds migrate and volatilize much slower than that of Catocene.So these compounds can be used as potential ferrocene-based burning rate catalysts.