J. Mater. Environ. Sci. 3 (2) (2012) 312-319 Haddad et al. ISSN : 2028-2508 CODEN: JMESCN 312 Synthesis, Differential Scanning Calorimetry (DSC) and Dielectric Relaxation Spectroscopy (DRS) Studies of N-methyl-N- propylpiperidinium Bis(trifluoromethylsulfonyl)imide Boumediene Haddad a,b, *, Didier Villemin b , El-habib Belarbi . a a Department of Chemistry, Synthesis and Catalysis Laboratory LSCT, Tiaret University, Tiaret, Algeria b LCMT, ENSICAEN, UMR 6507 CNRS, University of Caen, 6 bd Ml Juin, 14050 Caen, France Received in 18 Sept 2011, Revised x Jan 2012, Accepted x Jan 2012. * Corresponding author: Email: haddadboumediene@yahoo.com; Tel/Fax: +213 46 45 22 15. Abstract Ionic liquid based on N-methyl-N-propylpiperidinium [MPrPPI + ] cation and bis(trifluoromethanesulfonyl) imide [TFSI - ] anion has been synthesized and characterized. The synthesis is based on alkylation reaction of N-methylpiperidine followed by anion exchange. The structure of [MPrPPI + ][TFSI - ] was identified by using 1 H, 13 C, 19 F NMR and FT-IR spectroscopy. The phase behavior change for [MPrPPI + ][TFSI - ] was measured in the temperature range from -150 to 200 °C by using differential scanning calorimetry (DSC). In the frequency 10 -2 - 10 6 Hz range, dielectric measurements were performed on IL sample at various temperatures from -69 to -19 °C, i.e. around the glass transition temperature. The peak relaxation was observed near to this temperature. Also, in order to understand the ion dynamics in our IL, the frequency dependence of the complex conductivity (σ′, σ′′) of [MPrPPI + ][TFSI - ] at various temperatures has been analyzed. The relaxation has been characterized by the empirical Havriliak–Negami (H-N) equation. Keywords: Ionic liquids ILs; bis(trifluoromethanesulfonyl)imide anion; Differential Scanning Calorimetry (DSC); dielectric relaxation spectroscopy (DRS); Conductivity. 1. Introduction During the last decade, ionic liquids (ILs) have been considered as a promising green reaction media and as a novel solvent [1-4]. Initially, ILs were developed by electrochemists [5-8], who were looking for ideal electrolytes suitable for batteries [9-12]. Owing to the ionic environment effect on the chemical reactions [13- 16], the main focus of electrochemists was shifted to general ionic liquid characterization in view to better applications. Ionic liquids currently have a large variety application field, which continues to expand because of their use as electrolytes for devices and processes, and solvents for organic/catalytic processes and separation/ extraction [17-20]. In addition, other applications in enzyme catalysis and multiphase bio-process operations were reported [21]. According to literature [22], the physicochemical properties of room temperature ILs consisting of N-alkyl-N- methylpiperidinium bis(trifluoro methanesulfonyl) imides have been extensively studied, in particular for their high thermal stability [23-24]. Recently, piperidinium [TFSI - ] IL having a propyl and a methyl group have been prepared by many groups [25-31]. Sakaebe et al. [32,33] in their study of N-methyl-N- propylpiperidinium bis(trifluoromethanesulfonyl) imide proposed this ionic liquid as a attractive candidate for the electrolytes of Li-ion batteries with excellent safety characteristics. Which exhibited the electrochemical stability up to lithium reduction potential (<0V versus Li/Li + ) and excellent electrochemical properties. Since the data on dielectric properties e.g., (ε'), (ε"), (tanδ), (σ′) and σ′′ versus frequency, and thermal behaviour around the glass transition temperatures (T g ), of [MPrPPI + ][TFSI - ] not exist in the literature. These