Synthesis and characterization of new fluorinated copolymers based on azole groups for fuel cell membranes
Résumé
Two new fluorinated copolymers synthesized by grafting ω-hydroxyl pyrazolic (Trip) and triazolic (Trit) tripods onto poly(chlorotrifluoroethylene-alt-2-iodoethyl vinyl ether) copolymer (poly(CTFE-alt-IEVE) are reported.
These copolymers were prepared in two steps: the ω-hydroxy nitrogenous heterocycles reacted with iodine atoms
of poly(CTFE-alt-IEVE) copolymer followed by the deprotection of the benzyl group. The chemical structures
of tripod monomers and resulting copolymers were characterized by nuclear magnetic resonance and infrared
spectroscopies, elemental analysis, and mass spectrometry. The first analysis allowed one to determine the degree
of grafting that reached 80 and 19% for copolymers bearing pyrazole and triazole, respectively. Membranes
were processed in pellet form by compressing these copolymers. Thermal properties of the membranes,
examined by thermogravimetric analysis and differential scanning calorimetry, showed that such copolymers
were thermally stable up to 200°C under air, and exhibited glass transition temperatures ranging between 31
and 47°C. The temperature dependence of conductivity led to a simple Arrhenius behavior for both copolymers.
Poly(CTFE-alt-IEVE)-dep-Trit19% and poly(CTFE-alt-IEVE)-dep-Trip80% copolymers had a maximum proton
conductivity of 1.3 10−3 and 5.91 10−5mS/cm respectively at 180°C under quasi-anhydrous conditions. Cyclic
Voltammetry (CV) study illustrated that the electrochemical stability d