New anion conducting membranes based on functionalized styrene–butadiene–styrene triblock copolymer for fuel cells applications

Authors

  • Marco Faraj,

    1. Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, I-56126 Pisa, Italy
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  • Elisabetta Elia,

    1. Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, I-56126 Pisa, Italy
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  • Massimiliano Boccia,

    1. Acta S.p.A., via di Lavoria 56/G, I-56042 Crespina (PI), Italy
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  • Antonio Filpi,

    1. Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, I-56126 Pisa, Italy
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  • Andrea Pucci,

    Corresponding author
    1. Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, I-56126 Pisa, Italy
    2. CNR NANO, Istituto Nanoscienze-CNR, piazza San Silvestro 12, I-56127 Pisa, Italy
    3. INSTM, Unità di Ricerca di Pisa, Via Risorgimento 35, 56126 Pisa, Italy
    • Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, I-56126 Pisa, Italy
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  • Francesco Ciardelli

    1. Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, I-56126 Pisa, Italy
    2. Spin-Pet s.r.l., Via Risorgimento 35, 56126 Pisa, Italy
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Abstract

In this work, the functionalization of polystyrene-b-poly(butadiene)-b-polystyrene triblock copolymer (SBS) with vinylbenzyl chloride and benzoyl peroxide (BPO) or α,α′-azo-bis-isobutyronitrile (AIBN) as free radical initiators was reported. The functionalization degree (FD), calculated by 1H NMR spectroscopy and confirmed by elemental analysis, was highly tunable (from 4 to 10 mol %) and positively correlated to the starting percentage of radical initiator. More specifically, at the same initiator molar percentage grafting efficiency is higher using BPO rather than AIBN. Quaternization reaction of the grafted benzyl chloride groups with the bifunctional tertiary amine 1,4-diazabicyclo[2.2.2]octane (Dabco) led to a chemically and thermally stable homogeneous anion-exchange membrane. Electrochemical parameters were evaluated for Dabco-quaternized grafted copolymers having different FDs, and compared with a commercial Tokuyama benchmark membrane. Experimental data showed a positive correlation between FD and both water swelling and ionic conductivity. Best trade-off between ionic conductivity and water swelling was found for membrane having FD 9.1 mol %, which conductivity is comparable with the Tokuyama benchmark one and water uptake is only slightly higher. The results are discussed based on the molecular parameters with particular reference to ionic content and distribution. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

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