Fluorinated Polymers Based On Pyrazole Groups For Fuel Cell Membranes

Author

• Tarik Harit^a, 
• Fouad Malek^a, 
• Bruno Ameduri^b, , 

• ^a Laboratoire de Chimie Organique, Macromoléculaire et Produits Naturels – URAC 25, Faculté des Sciences, BP : 717, Bd Mohamed VI, 60 000 Oujda, Morocco
• ^b Ingénierie et Architectures Macromoléculaires, Institut Charles Gerhardt UMR – CNRS 5253, 8, Rue de l’école Normale, ENSCM, 34296 Montpellier, France

Received 5 February 2016, Revised 11 April 2016, Accepted 18 April 2016, Available online 19 April 2016

Highlights

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Fluorinated copolymers bearing pyrazole group as precursor of proton-conducting membranes.

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1-Benzyl-5-methyl-3-hydroxymethyl-pyrazole was synthesized and then grafted onto poly(CTFE-alt-IEVE) copolymer.

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Deprotection of the benzyl group produced poly(CTFE-alt-IEVE)-dep-pyrazole_y%copolymers.

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NMR spectroscopy enabled to monitor all reaction steps.

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Copolymers processed into membranes with proton conductivity of 4 × 10⁻⁵ mS cm⁻¹ at 180 °C.

Abstract

The 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 h, respectively. Deprotection of the benzyl group produced poly(CTFE-alt-IEVE)-dep-pyrazole_y% copolymers. NMR spectroscopy enabled to monitor all reaction steps and ensured the purity of these functional fluorinated copolymers. The poly(CTFE-alt-IEVE)-dep-pyrazole_y% 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.

Graphical abstract

Keywords

• Alternating copolymers; 
• Chlorotrifluoroethylene; 
• Conductivity; 
• Fluoropolymers; 
• Nuclear magnetic resonance; 
• Proton exchange membrane fuel cell; 
• Pyrazole

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http://www.sciencedirect.com/science/article/pii/S0014305716302774