Fluorinated polymers based on pyrazole groups for fuel cellmembranes

International audienceThe synthesis and characterization of two fluorinated copolymers bearing pyrazole group as precursor of proton-conducting membranes in polymer electrolyte fuel cells are described. 1-Benzyl-5-methyl-3-hydroxymethyl-pyrazole was first synthesized in a two step-reaction. It was then grafted onto poly(chlorotrifluoroethylene -alt-2-iodoethyl vinyl ether) copolymer (poly(CTFE-alt-IEVE)). The degree of grafting was controlled by the reaction time, and reached 30 and 55% after 24 and 48 hours, respectively. Deprotection of the benzyl group produced poly(CTFE-alt-IEVE)-dep-pyrazoley% copolymers. NMR spectroscopy enabled to monitor all reaction steps and ensured the purity of these functional fluorinated copolymers. The poly(CTFE-alt-IEVE)-dep-pyrazoley% copolymers were thermally stable (up to 200 °C under air) and showed a maximum proton conductivity of 4×10-5 mS.cm-1 at 180 °C under anhydrous conditions. From cyclic voltammetry (CV), these copolymers displayed an electrochemical stability domain extended over 2.0 V