Synthesis and Properties of Room-Temperature Choline Carboxylate Zwitterionic Ionic Liquids as Potential Electrolytes

Authors

  • Ângelo Rocha,

    1. IBB–Institute for Biotechnology and Bioengineering, Centre for Biological and Chemical Engineering, Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal), Fax: (+351) 218419062
    2. REQUIMTE/CQFB, Departamento de Química FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal)
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  • Tânia Carvalho,

    1. REQUIMTE/CQFB, Departamento de Química FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal)
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  • Dr. Pedro Vidinha,

    1. REQUIMTE/CQFB, Departamento de Química FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal)
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  • Dr. Nuno M. T. Lourenço

    Corresponding author
    1. IBB–Institute for Biotechnology and Bioengineering, Centre for Biological and Chemical Engineering, Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal), Fax: (+351) 218419062
    • IBB–Institute for Biotechnology and Bioengineering, Centre for Biological and Chemical Engineering, Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal), Fax: (+351) 218419062
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Abstract

Choline carboxylate zwitterions were prepared by two different synthetic routes through esterification of choline salts with a range of anhydrides. Their conjugation with lithium bis(trifluoromethylsulfonyl)imide resulted in the formation of stable room-temperature ionic liquids. In view of their use as potential electrolytes the physicochemical characterization of these attractive ionic liquids was performed. These compounds presented a glass transition temperature between −43 and −34 °C, good thermal stability up to 224 °C, densities above 1.44 g cm−3 at 25 °C, and viscosities between 3.56 and 12.27 Pa s at 25 °C. In terms of conductivity the most promising ionic liquid showed an excellent conductivity between 8.66×10−5 S cm−1 at 25 °C and 1.80×10−3 S cm−1 at 90 °C. These zwitterionic ionic liquids maintained a liquid state, and no dissociation was observed even after six months of storage at room temperature.

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