Synthesis of Pyrrolidinium-Based Poly(ionic liquid) Electrolytes with Poly(ethylene glycol) Side Chains

Abstract

The synthesis and characterization of a new family of pyrrolidinium based poly(ionic liquid) (PIL) electrolytes with poly(ethylene glycol) (PEG) pendant groups is reported. The PILs were synthesized from a diallyl methyl amine hydrochloride monomer, which was obtained in large quantities using a modified Eschweiler-Clarke reaction. As additional plasticizers for the PILs, pyrrolidinium ionic liquids (ILs), also with PEG groups, were synthesized. All obtained PILs and ILs revealed excellent thermal stabilities to greater than 300 °C. Binary electrolyte mixtures were prepared by blending the PILs and ILs in different weight ratios. In addition, a ternary mixture of the best performing PIL and IL and bis(trifluoromethane)sulfonimide lithium salt (LiTFSI) was prepared. The obtained electrolyte blends showed very good ionic conductivities in the best case up to 2.4 mS cm–1 at 25 °C and 10.2 mS cm–1 at 100 °C and outperformed their pyrrolidinium counterparts with alkyl side chain that were synthesized as a reference. It was found that the ionic conductivity of the blends increased with an increase in the PEG chain length of the PILs. The good physicochemical properties of the presented materials make them potential candidates for electrochemical applications such as lithium-ion batteries or dye-sensitized solar cells.

Ionic Liquid for High Voltage Supercapacitor

“…Certain characteristics of IL such as negligible vapor pressure, thermal stability, nonflammability, relatively high ionic conductivity, and broad electrochemical stability window are transferred to the polymer chain (from oligomers to high molecular weight polymers) [85]. Various PIL structures and properties are required for various applications of polymer electrolytes, electrochemical devices, smart materials, catalyst supports, porous polymer structures, and antibacterial PILs.…”

“…Therefore, the ionic conductivity of PIL is generally lower than that of monomeric ILs ionic conductivity. This phenomenon is due to the significant increment of glass transition temperature (T g ) and depletion of mobile ions after covalent or ionic bonding [85]. The ionic conductivity of PIL is affected by polymer architecture, molecular weight, and chemical nature of polymer chains.…”

Poly(ethylene glycol)‐Based Ionic Liquids: Properties and Uses as Alternative Solvents in Organic Synthesis and Catalysis

“…[13,[56][57][58] The rheological behavior, ionic conductivity, or thermophysical properties can be finely tuned by chemical modifications of the anion or cation for specific applications, for use as solid electrolytes in electrochemical devices for energy conversion, or for use as dipolar media in chemical applications, especially for reactions under microwave irradiation. [7,52,[59][60][61] 3.1. Thermal analysis: Glass transition and melting point…”

“…Moreover, the values of T g reported by Binder and co-workers [49] for dicationic ILs also depended on the PEG size, as well as on the chemical nature of both the counteranion and cationic group. [49,51,59] …”

“…[9,59] Therefore, the decomposition temperatures (T d ) of the IL PEG s were increased by a PEG chain long enough to wrap around the cationic head, which was expected to hinder nucleophilic attack of the anion involved in the thermal decomposition of the IL cation. [63] …”