Synthesis and characterization of ferrocenyl-functionalized polyester dendrimers and catalytic performance for thermal decomposition of ammonium perchlorate

A novel ferrocene functionalized polyester dendrimer (PEDr-Fc) containing 6, 12 and 24 peripheral ferrocene moieties were obtained using the esterification reaction between ferrocene carboxylic and polyester dendrimer (PEDr). The ¹H NMR, ¹³C NMR, MALDI-TOF mass spectra and elemental analysis techniques confirmed the structure of PEDr-Fc and provided evidences of the successful functionalization of PEDr by ferrocene with high yield over 92% and high grafting rate (more than 91%) of ferrocene on the terminals of dendrimer. The cyclic voltammogram measurements were carried out to analyze the redox properties of PEDr-Fcs. The catalytic performances for thermal decomposition of ammonium perchlorate (AP) were investigated by DSC techniques. The kinetic parameters were computed by the Kissinger method. PEDr-Fcs maintained the special redox properties by electron transfer of ferrocene/ferrocenium in ferrocene groups and all the redox centers were equivalent with no interaction between them. The electrode reactions of PEDr-Fcs were diffusion-controlled redox processes. PEDr-Fc presented an efficient catalytic effect on the thermal degradation of AP and the catalytic reactions were characterized by decreased activation energy and increased rate constant of thermal decomposition. The possible catalytic mechanism was that the electron transfer between Fe ²⁺ and Fe ³⁺ in ferrocene oxidized by AP and reduced by NH ₃ produced by the degradation of AP accelerated decomposition reaction below 300 °C, and the formation of iron clusters with large surface areas might cause the rupture of the chemical bond in AP at high temperature.