Polymerized Ionic Liquids with Polythiophene Backbones: Self-Assembly, Thermal Properties, and Ion Conduction

Abstract

Single ion conductors, based on polymerized ionic liquids (PILs) with a polythiophene backbone bearing imidazolium salts with butyl, hexyl, octyl, and decyl side groups and six different counteranions ([Br]−, [BF4]−, [ClO4]−, [PF6]−, picrate, and [B­(Ph)4]−), are synthesized and studied with respect to the thermal, structural, and ion-conductivity properties. PILs bearing the polythiophene backbone are unique as they can simultaneously conduct electronic charge and ions at nanometer length scales. In addition, the π–π stacking of the polythiophene backbones results in exceptional smectic-like order. Increasing side group length from butyl to decyl increases the room temperature conductivity by 4 orders of magnitude (internal plasticization). Anion size (anionic radii from 0.19 to 0.44 nm) affects both the structure (from smectic-like to amorphous with increasing anion radius) and the ionic conductivity. Conductivity values differ by 6 orders of magnitude by varying anion size at ambient temperature. As a result, conductivities as high as 2 × 10–3 S/cm could be obtained at high temperatures. Differences in conductivity are discussed in terms of changes in glass temperature (T g), anion size, and value of dielectric permittivity. Overall ion transport in PILs based on polythiophene backbones is controlled by the low T g, value of dielectric permittivity, smectic layering, and ion association lengths not exceeding a single smectic layer.

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

“…2,50,51 Ionic liquid moieties can be covalently tethered to a conjugated polymer backbone to enable ion conduction without the presence of solvent, which is particularly important for solvent-free electrochemical devices. 1,2,53 Mixed conducting conjugated materials are commonly employed as protective coatings and binders for cathode materials in batteries due to their easy processability and facile ion and electron transport in the presence of liquid electrolyte. 18,[54][55][56][57][58] Increasing interest in solventfree battery construction, however, has created a demand for materials that can conduct both ions and electrons without the presence of solvent.…”

“…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.…”

Molecular Weight-Dependent Physical and Photovoltaic Properties of Poly(3-alkylthiophene)s with Butyl, Hexyl, and Octyl Side-Chains

“…Poly-3-alkylthiophenes (P3ATs) have been intensively investigated and developed for use in various organic electronic devices, such as organic light-emitting diodes [ 1 ], organic photovoltaic cells (OPVs) [ 2 , 3 , 4 , 5 , 6 ], and organic field-effect transistors [ 7 , 8 ], because of their easy deposition from solution onto various types of substrates and low preparation cost [ 9 ]. In OPVs, the polymer is known to be an effective semiconducting material with a relatively high hole mobility [ 10 , 11 , 12 ] and self-assembly capacity [ 13 , 14 ].…”

Machine Learning Solvation Environments in Conductive Polymers: Application to ProDOT-2Hex with Solvent Swelling

“…This conclusion is further supported by the average Li-O 2 CDFs shown in Figure 4A, which demonstrate that SEs (1), (2), (3) and (4) exhibit precise numbers of oxygen atoms (two, one, two and three, respectively). It is known that oxygen atoms play a crucial role in Li + solvation, 13,41 however the SEC approach identifies the oxygen atoms as the main feature of classification without this prior knowledge, which suggests that our approach may be used for cases where the important solvation interactions are not known a priori. Figure 3 also shows that SEs (1) and 3, both of which have two oxygen atoms in the immediate solvation shell, are distinguished from each-other based on the Li-H cap pair; SE(1) comprises two H cap atoms while SE(2) contains none.…”