What Determines the Glass Temperature and dc-Conductivity in Imidazolium-Polymerized Ionic Liquids with a Polythiophene Backbone?

Abstract

We report the results of a combined work based on density functional theory (DFT) calculations and experiments of the factors that influence the glass temperature, T g , and the associated ion conductivity in polymerized ionic liquids bearing imidazolium salts in the side group. This study consists of four different N-alkyl side-chain lengths [with n = 4 (butyl), 6 (hexyl), 8 (octyl), and 10 (decyl)] and seven different counteranionsDFT calculations of the anion−cation complexation energies were combined with thermodynamics (differential scanning calorimetry), structural (X-ray scattering), as well as temperature-and pressure-dependent dielectric spectroscopy measurements of ion conduction. Our results show that ion conduction is facilitated by local anion jumps with a length scale on the order of the charge alteration distance. Ion complexation strongly influences the backbone dynamics and the associated T g . A simple "stick and jump" model can account for the increased backbone mobility (reduced T g ) and the concomitant enhanced ion conductivity for anions with intermediate size. Among the different anions, [TFSI] − with its comparably large size and broad charge delocalization is only weakly coordinated with the cation. This best facilitates anion motion within the "ion paths" of the hexagonally packed cylinders and smectic morphologies.

Li+ and Oxidant Addition To Control Ionic and Electronic Conduction in Ionic Liquid-Functionalized Conjugated Polymers

“…61,62 Polythiophenes with imidazolium side chains have shown intrinsic ionic conductivity up to 10 -4 S cm -1 in the neat state, while also showing evidence of significant long-range order in scattering studies. 60,63 While Ionic liquid functionalized conjugated polymers show potential as solvent-free mixed ion and electron conductors, to this point there have been few studies that investigate lithium-ion conduction in ionic liquid functionalized conjugated polymers. Furthermore, very few studies have characterized mixed conduction in conjugated systems upon simultaneous salt addition and oxidant addition.…”

“…This is indicative of a lamellar structure with domains comprised of the π-stacked conjugated backbone and the side chains. 59,60 Note that the charge side groups are nanophase-separated from the thiophene backbone, and confined to a lamellar domain. As a result, it is likely that added salt will partition into the more polar side-chain stacking region.…”

Cationic Diazapentacenium Polymers Made in a Sequence of CN Cross Coupling Polymerization and Acid‐Mediated Postpolymerization Cyclization

“…Counter ion exchange in such ionic polymers can be simply achieved by dialysis (see refs. [16,17]). The ionic nature of the target polymers will enable the solution processing of multilayer assemblies, in combination with non-polar component(s), in the so-called orthogonal solvents approach.…”

Ionic Conductivity in Polyfluorene-Based Diblock Copolymers Comprising Nanodomains of a Polymerized Ionic Liquid and a Solid Polymer Electrolyte Doped with LiTFSI

“…18,19 The ionic conductivity in pure PILs has been extensively studied in earlier studies 20−28 as well as the factors that determine the segmental dynamics (glass temperature) and concomitantly the ion motion. 22 Furthermore, the design of PILs bearing a πconjugated backbone can lead to simultaneous conduction of both ions and electrons at the nanometer length scale. 21,22,29 In this endeavor, polyfluorenes (PFs) emerged as a promising class of π-conjugated polymers.…”

“…22 Furthermore, the design of PILs bearing a πconjugated backbone can lead to simultaneous conduction of both ions and electrons at the nanometer length scale. 21,22,29 In this endeavor, polyfluorenes (PFs) emerged as a promising class of π-conjugated polymers. Neutral PF derivatives exhibit wide band gaps in the range from 2.8 to 3.5 eV.…”