Ferrocene End-Cap Hyperbranched Poly (amine-ester): Structure and Catalytic Performance for Thermal Decomposition of Ammonium Perchlorate

Second to fourth generation (G2-G4) ferrocene end-cap hyperbranched poly (amine-ester) (HPAE-CP-Fe) was successfully synthesized by esterification of ferrocenecarboxylic acid and hyperbranched poly (amine-ester) (HPAE). The ¹H-NMR, ¹³C-NMR, FTIR, and mass spectra confirmed the structure of HPAE-CP-Fe and provided evidence of the successful modification of ferrocene to HPAE. The thermal behavior and catalytic performance for thermal decomposition of ammonium perchlorate (AP) were investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC). Activation energy and kinetic parameters were computed by the Kissinger method. The results indicated that HPAE-CP-Fe was more thermally stable than pure HPAE and that the ferrocenyl groups could efficiently improve the thermal stability of HPAE. Low- and high-temperature exothermic peaks of AP decreased with the addition of G2-G4 HPAE-CP-Fe into AP. Catalytic reactions were characterized by decreased activation energy and increased rate constant for thermal decomposition. An efficient catalytic effect of HPAE-CP-Fe on the thermal degradation of AP was observed. A possible catalytic mechanism was proposed where the electron transfer from Fe ²⁺ to Fe ³⁺ in ferrocene oxidized by AP accelerated the decomposition reaction under 300 °C. The formation of iron clusters with large surface areas may cause the rupture of the chemical bond in AP at high temperature.