Thermodynamic Parameters of Non-isothermal Degradation of a New Family of Organometallic Dendrimer with Isoconversional Methods

The objective of this work is to obtain the thermodynamic parameters (the changes in enthalpy, Gibbs free energy, and entropy) of two degradation steps observed in three novel families of organometallic dendrimers. The isoconversional Flynn–Wall–Ozawa (FWO) model was employed to calculate the effective activation energy and pre-exponential factor. The changes in enthalpy and the entropy revealed a quite consistent tendency with the activation energy whereas the change of Gibbs free energy always remained positive during the whole degradation process, which demonstrated the implication that the degradation is non-spontaneous and thus requires an external heat supply

Thermal Degradation Behavior of a New Family of Organometallic Dendrimer

Organometallic dendrimers are one of the most attractive macromolecules owing to their unique properties that derived from the combination of the metallic moieties and the remarkable architecture of the dendrimers. A new family of organoiron dendrimers has been synthesized using divergent methodology. To gain insight into the stability of these dendrimers, we investigated their thermal property using nonisothermal thermogravimetry analysis (TGA), which reveal the kinetic triplets, the pre-exponential factor, the effective activation energy and the reaction model involved in their thermal degradation. The results were obtained at heating rates of 10, 15 and 20 °C min −1 . Four nonisothermal methods, the Friedman, the Ozawa and Flynn and Wall, the Kissinger–Akahira–Sunose and the Minimizing were used to investigate the variation of the effective activation energy with the extent of crystallization and, hence, with temperature. In addition, the activation energy was calculated from isothermal data. The degradation mechanism follows the Avrami–Erofeev mechanism for solid-state reaction models. Graphic Abstrac