Thermal and Electrochemical Properties of Ionic Liquids Bearing Allyl Group with Sulfonate-Based Anions-Application Potential in Epoxy Resin Curing Process

Sulfonate-based ionic liquids (ILs) with allyl-containing cations have been previously obtained by us, however, the present study aims to investigate the thermal, electrochemical and curing properties of these ILs. To determine the temperature range in which ionic liquid maintains a liquid state, thermal properties must be examined using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Melting, cold crystallization and glass transition temperatures are discussed, as well as decomposition temperatures for imidazolium- and pyridinium-based ionic liquids. The conductivity and electrochemical stability ranges were studied in order to investigate their potential applicability as electrolytes. Finally, the potential of triflate-based ILs as polymerization initiators for epoxy resins was proven.

Gel Polymer Electrolytes with Mixture of Triazolium Ionic Liquids and Propylene Carbonate

This study is focused on the structural influence of 1,2,4-triazolium ionic liquid (IL), that is, the effect of the length of the substituent and the type of substitution (1-methyl-4-alkyl or 1-alkyl-4-methyl) used in the mixture with propylene carbonate (PC) on the properties of thiol–ene polymer ionogels and on the preparation of an ionogel with satisfactory mechanical and conductive properties. PC allows for higher conductivity but also causes electrolyte leakage from the gel. When using triazolium IL (instead of the imidazolium one), because of the stronger interactions between components of the system, the ionogels do not leak. In this study, 1,4-dialkyl-1,2,4-triazolium ILs were successfully synthesized by the alkylation of 1,2,4-triazole. Subsequently, gel polymer electrolytes were obtained by one-pot thiol–ene photopolymerization reactions of tetrafunctional thiols with different chemical structures: pentaerythritol tetra(3-mercaptopropionate) (PETMP) or pentaerythritol tetra(3-mercaptobutyrate) (PETMB) and trifunctional ene (TATT) in the presence of a mixture of 1,4-dialkyl-1,2,4-triazolium IL with PC. Measurements made by electrochemical impedance spectroscopy showed that all ionogels with TATT+PETMB as a polymer matrix presented smaller relative ionic conductivity compared to ionogels containing TATT+PETMP. The puncture resistance and elongation at puncture, measured by the puncture resistance method, were higher for ionogels with poly(TATT+PETMB) than for those with poly(TATT+PETMP). Moreover, ILs containing a methyl group in position N1 of the 1,2,4-triazole ring presented lower puncture resistance than ionogels with ILs containing a methyl group in position N4, especially for shorter alkyl chains. Additionally, the photo-differential scanning calorimetry method was employed to characterize the course of photopolymerization. The compositions and their constituents were characterized by UV and IR spectroscopy.