Thermal degradation behavior of ionic liquid/ fluorinated polymer composites: Effect of polymer type and ionic liquid anion and cation

Abstract

This work reports on the evaluation of the thermal degradation of poly(vinylidene fluoride) (PVDF) and PVDF co-polymer (PVDF-TrFE, PVDF-HFP and PVDF-CTFE) composite films with different imidazolium ionic liquids (ILs). The influence of the IL type, including cation and anion type, cation chain length and content up to 40 wt% were evaluated. Independently of the fluorinated polymer type, all neat samples present a single degradation step. Upon the incorporation of the IL [C2mim][TFSI] into the different polymers, a decrease in the thermal stability occurs, indicating the IL imidazolium interaction with the CH2-CF2 groups of the fluorinated matrix. Further, it was stablished that the thermal stability of the composite material decreases with increasing cation chain length. The Ozawa-Flynn-Wall and Kissinger models were applied to evaluate the activation energies of the samples during isothermal experiments, showing that the thermal degradation activation energy ranges from 161 ± 6 kJ.mol-1 ([C2mim][TFSI]/PVDF) to 131 ± 14 kJ.mol-1 ([C2mim][TFSI]/PVDF-CTFE). No large differences were observed on the effect of IL inclusion in PVDF, PVDF-TrFE, PVDF-HFP and PVDF-CTFE polymer matrices.