Synthesis, Characterization And Thermal Performance Study Of C₆0-PAMMO Itaconic Acid And C60-bis（2,4,6-trinitrophenethyl） Malonate Maleic Acid Lead/Copper Salts

Three energetic fullerene derivatives were synthesized and their thermal performances were investigated.First of all, a type of linear poly(3-azidomethyl-3-methyl oxetane)(PAMMO)with low molecular weight was designed and prepared using ethanol as initiator. Gel permeation chromatography(GPC) analysis showed that the number-average molecular weight(Mn), weight-average molecular weight(Mw), and polydispersity of the polymer were 718, 1027, and 1.43, respectively. PAMMO was subsequently introduced into the C60 cage, and a new functionalized fullerene derivative [60]fullerene poly(3-azidomethyl-3-methyl oxetane)(C60-PAMMO) was synthesized using a modified Bingel reaction of [60]fullerene(C60) and bromomalonic acid poly(3-azidomethyl-3-methyl oxetane) ester(BM-PAMMO). The product was characterized by fourier transform infrared(FTIR), ultraviolet-visible(UV-vis), and nuclear magnetic resonance(NMR) spectroscopy analyses. Results confirmed the successful preparation of C60-PAMMO. Moreover, the thermal decomposition of C60-PAMMO was analyzed by differential thermal analysis(DTA), thermogravimetric analysis coupled with infrared spectroscopy(TG-IR), and in situ FTIR. The decomposition of C60-PAMMO showed a three-step thermal process. The first step at approximately 150 ℃ was related to the cycloaddition of azido groups(-N3) with[60]fullerene. The second step was ascribed to the remainder decomposition of the PAMMO main chain at approximately 230 °C. The final step was attributed to the burning decomposition of amorphous carbon, the main chain, N-heterocyclic and carbon cage at around 510 ℃.Target product 1 and 2, C60-PAMMO itaconic acid lead/copper salts, were synthesized via reaction of C60-PAMMO, itaconic acid, lead nitrate and copper nitrate as raw materials. C60-PAMMO itaconic acid copolymer was prepared with C60-PAMMO and itaconic acid via copolymerization. Afterwards, the C60-PAMMO itaconic acid copolymer metal salts including(Pb and Cu) were prepared with C60-PAMMO itaconic acid copolymer and various corresponding nitrates. C60-PAMMO itaconic acid copolymer metal salts were analyzed and determinated by FT-IR, UV-Vis,X-ray diffractio(XRD) and X-ray photoelectron spectroscopy(XPS). The thermalstability of C60-PAMMO itaconic acid lead salt was carried out by DTA and TG under air, which showed a good thermal stability. The thermal decomposition behaviors were studied under heating rates as 10 ℃·min-1, 15 ℃·min-1, 20 ℃·min-1, and 30 ℃·min-1.Kissinger method and Ozawa method were used to calculate the activation energy Ea and pre-exponential factor A of the sample.On this basis, target product 3, C60-bis(2,4,6-Trinitrophenethyl) malonate(C60-TNPEM) maleic acid lead salt, was synthesized via reaction of C60-TNPEM maleic acid polymer and lead nitrate. The synthesis of C60-TNPEM with a yield of 37%(based on the consumed C60) through Bingel reaction of bis(2,4,6-trinitrophenethyl) malonate(TNPEM) and C60. To be exact, TNPEM with a yield of 65% could be synthesized through esterification of malonyl dichloride and 2,4,6-trinitrophenyl ethanol(TNPE).TNPE was prepared by the reaction of TNT and formaldehyde as raw materials under a weak base condition. Moreove, the structure of the products were characterized by FT-IR, UV-Vis, 1H NMR, 13 C NMR, etc. The thermal stability of C60-TNPEM maleic acid lead salt was also carried out by DTA and TGA under air. The results showed that the product has good thermal stability. At the same time, C60-TNPEM maleic acid lead salt was added to the principal components of propellants as the combustion catalyst to study the catalyst behavior. The results showed that C60-TNPEM maleic acid lead salt could accelerate the thermal decomposition of RDX.