A group contribution method for estimation of glass-transition temperature of 1,3-dialkylimidazolium ionic liquids Farhad Gharagheizi • Mohammad Hossein Keshavarz • Poorandokht Ilani-Kashkouli • Nasrin Farahani • Kaniki Tumba Received: 25 June 2012 / Accepted: 17 December 2012 Ó Akade ´miai Kiado ´, Budapest, Hungary 2013 Abstract Glass-transition temperature (T g ) of ionic liq- uids (ILs) plays a key role in assessment of their potential for electrolyte application purposes. In this communica- tion, a new group contribution model is presented for the prediction of the T g of 1,3-dialkylimidazolium, a class of ILs, which has great potentialities to serve as electrolyte. To develop this model, the contribution of ILs’ anions and cations is separately considered. This simple model shows a low average relative deviation of 1.94 % for a data set including 109 experimental glass-transition temperature. Keywords Glass-transition temperature  Ionic liquids  Group contribution  Reliable model List of symbols K molecular conductivity Z Ion charge e 0 Electronic charge F The Faraday constant D Diffusion coefficient k B Boltzmann’s constant N A Avogadro’s number T g Glass-transition temperature T 0 Reference temperature Introduction Electrolytes and electrolyte solutions are considered as an essential part in electrochemical devices like fuel cells, capacitors, and batteries. Their main task is to provide a suitable medium for conducting electricity. A mixture of salts and polar solvents is a good option for this purpose. The amount of ionic conductivity in these solutions directly depends on the nature of the dissolved salts. The role of polar solvent is to boost the degree of salts dissociation in order to supply sufficient amount of ions in the solution. Although, these conventional solutions show high ionic conductivity, they have some drawbacks. They are usually corrosive, flammable, and toxic. These features cast doubt on their future applications [1]. Therefore, finding some appropriate alternative electrolytes is of great importance for researchers dealing with this field. These candidates should possess high ionic conductivity and electrochemical stability as well as non-volatile and non-toxic nature. A potential candidate for substitution of conventional electrolytes is a new ion conductive materials called ‘‘Ionic Liquids (ILs)’’. ILs [2–16] is the class of liquids which entirely composed of ions and fluid at temperature below Electronic supplementary material The online version of this article (doi:10.1007/s10973-012-2907-0) contains supplementary material, which is available to authorized users. F. Gharagheizi (&)  P. Ilani-Kashkouli Department of Chemical Engineering, Islamic Azad University, Buinzahra Branch, Buinzahra, Iran e-mail: fghara@ut.ac.ir; fghara@gmail.com M. H. Keshavarz Department of Chemistry, Malek-ashtar University of Technology, Shahin-shahr, P.O. Box 83145/115, Isfahan, Islamic Republic of Iran N. Farahani Department of Chemistry, Islamic Azad University, Buinzahra Branch, Buinzahra, Iran K. Tumba Department of Chemical Engineering, Mangosuthu University of Technology, Durban, South Africa 123 J Therm Anal Calorim DOI 10.1007/s10973-012-2907-0