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

This work reports on the evaluation of the thermal degradation of poly(vinylidene fluoride) (PVDF) and PVDF copolymer (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.

Automated summary

This study evaluated the thermal degradation of poly(vinylidene fluoride) (PVDF) and its copolymers in composite films with different imidazolium ionic liquids (ILs), finding that the incorporation of ILs decreases thermal stability and longer cation chain lengths lead to decreased thermal stability in the composite material. Activation energy for thermal degradation ranged from 161 ± 6 kJ mol-1 to 131 ± 14 kJ mol-1, with no significant differences observed in the impact of IL inclusion in various polymer matrices.