Fluorinated poly(1,3,4-oxadiazole-ether)s. Thermooxidative stability and kinetic studies

• Thermal stability of new fluorinated poly(1,3,4-oxadiazole-ether)s is reported.
• The kinetic processing of thermogravimetric data was carried.
• The analysis of activation energy variation with the conversion degree is presented.
• During its first stage, the degradation process follows a F2 kinetic model.
• In the second stage, degradation occurred by reactions controlled by the R2 kinetic model.

Aromatic poly(1,3,4-oxadiazole-ether)s containing trifluoromethyl groups were synthesized by reacting 2,5-bis(p-fluorophenyl)-1,3,4-oxadiazole with three bisphenols, namely 4,4′-(hexafluoroisopropylidene)diphenol, (1a), 1,1-bis(4′-hydroxyphenyl)-1-(3′-trifluoromethylphenyl)-2,2,2-trifluoroethane, (1b), and 1,1-bis(4′-hydroxyphenyl)-1-(3′,5′-ditrifluoromethylphenyl)-2,2,2-trifluoroethane, (1c), or with mixtures of equimolar amounts of 1b or 1c and 9,9-bis(4-hydroxyphenyl)fluorene. The polymers were characterized by FTIR and 1H NMR spectroscopy, solubility, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The thermal decomposition behavior of the polymers was studied using TGA in air, at several heating rates between 7 and 16 °C min−1. The kinetic processing of thermogravimetric data was carried out using differential and integral methods, Friedman and the method suggested by Vyazovkin. The decomposition process of the polymers took place in two stages. The variation of activation energy with the conversion suggested for the first stage of decomposition a degradation mechanism by parallel or successive reactions, depending on the chemical structure of the polymers. For the second stage of decomposition the variation of activation energy with the conversion suggested for all the polymers a degradation mechanism consisting of successive reactions.

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