The body of work on polymerized ionic liquids has been growing rapidly in recent years as researchers expand the synthesis space to achieve novel membrane materials with high conductivity, excellent mechanical stability, and high transference number. Despite progress in identifying specific new polymers and useful properties, there has been limited agreement over the mechanism for ion transport in these materials. It is essential that we resolve said mechanism for polymerized-ionic-liquid conduction, with the goal of streamlining future material design. Molecular dynamics is an excellent tool for analyzing local coordination behavior, ion-hopping pathways, and other phenomena of length- and time-scales that are currently inaccessible to direct experimental observation. Ion transport is seen to proceed via a "climbing the ladder" mechanism involving the formation and breaking of ion-association pairs with, on average, four polymerized ions from two polymer chains. This results in a link between ion-association lifetime and diffusivity for chemically similar polymerized ionic liquids, a feature that distinguishes polymerized ionic liquids from a broad class of polymer electrolytes and low fragility ionomers. This is also shown to be the case for a set of backbone-polymerized ionic liquids, when compared to a chemically similar pendent-polymerized ionic liquid. This is particularly interesting because the pendent architectural motif proves to have significantly higher reversibility of ion-hopping events. The application of design rules inspired by this research has already led to the experimental discovery of highly decoupled polymerized ionic liquids with excellent conductivity at ambient temperature. Parametric simulation studies of poly(vinylimidazolium) polymerized ionic liquids and counterion variants have revealed a decoupling of ion mobility from polymer segmental dynamics. Small counterions are generally more decoupled, but results show that size is not the sole arbiter. For this set of different chemical components, encompassed by the anionic study, ion-association relaxation time, rather than lifetime, was proven to better correlate with diffusivity. Similar physics is observed between polymerized ionic liquids and salt-doped polymerized zwitterions for the population of mobile ions whose polymerized counter-charge is located on the end of a monomeric pendant. However, the cage-relaxation timescale appears to correlate better with diffusivity for the opposite ion in such materials

The series covers the fundamentals and applications of different smart material systems from renowned international experts.

Polymerized ionic liquids, polyILs, are a novel type of solid polymer electrolyte with possible applications in energy conversion or storage devices. The key to unlocking the true potential ionic conductivity and mechanical strength of polyILs lies in the strategic design of the chemical structure which, facilitates fast ion transport in a thermally stable material. To shed light onto the structure-property relationship in polymerized ionic liquids, this dissertation presents experimental studies on the impact of molecular structure and spatial confinement on ion dynamics in ammonium- and imidazolium-based polymerized ionic liquids with various chemical structures. Broadband dielectric spectroscopy is used alongside X-ray scattering and differential scanning calorimetry to investigate the impact of alkyl pendant group length and poly-cation chemical structure on counter-ion mobility. It is found that the ion mobility in ammonium-based polymerized ionic liquids is more sensitive to variation of the molecular surrounding of the poly-cation, compared to their imidazolium-based counterparts. Furthermore, it is shown that the cation chemistry plays a more significant role than the cation location relative to the backbone, which is an important design handle when selecting the molecular chemistry of the material for a specific application. Ultra thin polymer films have a large ratio of interface to bulk material, which due to electrostatic interactions and confinement effects, can drastically alter dielectric properties. Broadband dielectric spectroscopy in combination with a nano-structured electrode configuration is used to investigate ion dynamics in ultra-thin films of polymerized ionic liquids as thin as 7.5 nm. Ion dynamics remain unaltered at low temperatures, while a decrease in the characteristic ion hopping rate is observed above the Tg̳ of the bulk polyIL. With this experimental approach the structural relaxation of an ammonium based polymerized ionic liquid film of 15nm thickness is measured. The ionic conductivity and structural relaxation data presented in this work provides valuable strategic information for designing electrode materials compatible with solid polymer electrolyte thin films, and smart choice of chemical structures to avoid parasitic losses due to electrode polarization in thin film geometries.

This book summarizes the latest knowledge in the science and technology of ionic liquids and polymers in different areas. Ionic liquids (IL) are actively being investigated in polymer science and technology for a number of different applications. In the first part of the book the authors present the particular properties of ionic liquids as speciality solvents. The state-of-the art in the use of ionic liquids in polymer synthesis and modification reactions including polymer recycling is outlined. The second part focuses on the use of ionic liquids as speciality additives such as plasticizers or antistatic agents. The third part examines the use of ionic liquids in the design of functional polymers (usually called polymeric ionic liquids (PIL) or poly(ionic liquids)). Many important applications in diverse scientific and industrial areas rely on these polymers, like polymer electrolytes in electrochemical devices, building blocks in materials science, nanocomposites, gas membranes, innovative anion sensitive materials, smart surfaces, and a countless set range of emerging applications in different fields such as energy, optoelectronics, analytical chemistry, biotechnology, nanomedicine or catalysis.

Gel polymer electrolytes (GPEs) are ion-conducting polymers where the polymer matrix is swollen with a certain amount of solvent. While GPEs are able to take advantage of both the mechanical properties of the polymer matrix and the conductive properties of the solvent, they are limited due to the inverse relationship between the ionic conductivity ([sigma]o) and the modulus, diminishing their potential as next generation lithium-ion battery electrolytes. In this dissertation, we studied the fundamental properties of three different GPEs, molecular ionic composites (MICs) where the solvent is an ionic liquid (IL), single-ion-based MICs where the 'solvent' is poly(ethylene glycol), and cellulose-ionic liquid solutions, for their potential use as battery electrolytes. MICs utilize the mechanical and thermal stability of a rigid-rod sulfonated polyelectrolyte, poly(2,2')-disulfonyl-4,4'benzidine terephthalamide (PBDT), and the high conductivity, electrochemical stability, and low volatility of ILs. This allows the MICs to produce a simultaneous high modulus (from the PBDT) and a high conductivity (from the IL). The first half of this dissertation explores how the change in either the PBDT concentration with a constant IL or the IL molecular volume (Vm) and chemistry with a constant PBDT concentration affects both the mechanical and charge transport properties of the MICs. The varying PBDT concentration MICs were produced via an ion exchange method to form 3 mm diameter cylinders (ingots) while the varying IL Vm MICs were produced via solvent casting to form six free-standing films. The single-ion PBDT membranes were also formed via the solvent casting method. The mechanical properties were measured using a combination of oscillatory shear rheology and uniaxial tensile tests (only for the films), while the dielectric properties and morphology of the films were determined through dielectric relaxation spectroscopy (DRS) and atomic force microscopy (AFM) respectively. Increasing the MIC PBDT concentration with a constant IL, 1-butyl- 3-methylimidazolium tetrafluoroborate (BMIm-BF4), showed a minimal change in dynamic glass transition temperature (Tg) of roughly 2 °C through rheology with its respective IL. This allowed for the MIC ionic conductivity ([sigma]o) at elevated PBDT concentrations to be within a factor of two of the neat IL at room temperature while also producing a shear modulus (G') in the MPa range up to 200 °C. This is due to the MICs producing a two-phase environment corresponding to an IL-rich "puddle" phase and a PBDT-rich "bundle" phase, shown through the phase contrast in atomic force microscopy (AFM), where IL ions form alternating sheaths of cations and anions around each PBDT rod. As the PBDT concentration increases, these puddles shrink and produce a near single bundle phase. This potentially increases the polarizability of the MIC, shown by an increasing static dielectric constant, as well as allowing for more IL ions to contribute to [sigma]o shown by a decrease in the Haven ratio (HR), the ratio between the total number of charge carriers observed through NMR and the number conductive charge carriers that can be analyzed through the ionic conductivity. Incorporating ILs with different molecular volumes (Vm) and chemistries in the MICs with a constant PBDT concentration showed that all MICs maintain low Tgs, ranging between 0 -- 8 °C above their respective neat IL. This was confirmed through analyzing the derivative spectra from DRS to determine the dynamic Tg as well as measuring the thermal Tg through differential scanning calorimetry (DSC). The agreement in Tg between these two methods suggests that the glassy dynamics of MICs is dictated by the rearrangement of IL ions during charge transport. All MICs are able to produce high [sigma]o, ranging from 1 -- 6 mS cm-1 at 30 °C with smaller imidazolium-based cations producing higher [sigma]o than MICs with larger imidazolium cations and similar anions due to their larger molar conductivity. Tensile measurements showed that all MICs produce IL-dependent Young's modulus (E), ranging from 50 -- 500 MPa at 30 °C, up to 60 x higher when compared to the G' of the same MICs. We propose this is due the difference in the distribution of PBDT chains between the shear and tensile planes as well as the competing interactions between the IL ions and the PBDT rods. This hypothesis is supported by the AFM phase contrast images, where the 1-ethyl- 3-methylimidazolium (EMIm+) based MICs show the largest formation of the bundle phase (with very small puddles) while the BMIm+ based MICs produce a larger puddle phases as the anion Vm decreases, thus lowering E. Relating the [sigma]o to their corresponding diffusive coefficients through the Nernst-Einstein shows that all MIC have an ionicity (inverse Haven ratio, HR--1) range between 0.54 -- 0.63, suggesting that a fraction of the diffusive ions do not contribute to charge transport. Along with the IL-based MICs, we analyzed the dielectric and mechanical dynamics of single-ion conducting PBDT-based membranes by incorporating poly(ethylene glycol) with a molecular weight of 400 g mol-1 (PEG400) and either Na+ or Li+ counterions are studied in detail. Varying the PBDT and PEG400 wt% allowed for the preparation of varying PBDT concentrated membranes. All membranes have low DSC Tgs, regardless of counterion attached to the PBDT and the Tg increases with elevated PBDT concentration. The ionic conductivity of the membranes systematically decreases with increasing PBDT concentration, ranging from 0.1 -- 7 [mu]S cm-1` at 30 °C and reaching 100 [mu]S cm-1 at 120 °C in the lowest NaPBDT concentration film. Normalizing the temperature-dependent ionic conductivities divided by their respective Coulombic dielectric constant by the dynamic DRS Tg show that all data roughly collapse onto a single curve, suggesting that the glassy dynamics are dictated the speed of the diffusive motion and the dissociation of ion-pairs produced from strong ionic interactions in the membrane. Tensile stress-strain analysis on the membranes reveal that the E is dominated by the counterion used with the Na+-based membranes producing an E ranging from approximately 100 -- 400 MPa while the Li+-based membranes produced an E ranging from approximately 300 -- 2100 MPa. We suggest that Li+ counterions forms a stronger network with the PBDT sulfonate groups off of the PBDT than the Na+ counterions. The smaller Li+ binds to the sulfonates on the PBDT chain more strongly, confirming that the modulus of this class of materials has ionic origins. We investigated the dielectric dynamics of cellulose in ILs through DRS to understand the fundamental properties of cellulose-IL solutions with varying cellulose concentration and IL. Like the MICs, the cellulose-IL solutions showed relatively high ionic conductivity compared to their respective neat IL, all within a factor of 4 at 30 °C at the highest cellulose concentration, as well as minimal increase in the dynamic DRS Tg (up to 10 °C). The ionic conductivity normalized by the DRS Tg show all data collapsing on a single curve with each IL suggesting that the glassy dynamics in these solutions is dictated by the ion arrangement produced on charge transport. Additionally, increasing the cellulose concentration increases the static dielectric constant relative to the neat ILs suggesting the association between the cellulose and IL ions enhances the polarizability of the solution over the neat IL.

Polymerized ionic liquids (PolyILs) are promising materials for various solid state electronic applications such as dye-sensitized solar cells, lithium batteries, actuators, field-effect transistors, light emitting electrochemical cells, and electrochromic devices. However, fundamental understanding of interconnection between ionic transport and mechanical properties in PolyILs is far from complete. In this paper, local charge transport and structural changes in films of a PolyIL are studied using an integrated experiment-theory based approach. Experimental data for the kinetics of charging and steady state current-voltage relations can be explained by taking into account the dissociation of ions under an applied electric field (known as the Wien effect). Onsager's theory of the Wien effect coupled with the Poisson-Nernst-Planck formalism for the charge transport is found to be in excellent agreement with the experimental results. The agreement between the theory and experiments allows us to predict structural properties of the PolyIL films. We have observed significant softening of the PolyIL films beyond certain threshold voltages and formation of holes under a scanning probe microscopy (SPM) tip, through which an electric field was applied. Finally, the observed softening is explained by the theory of depression in glass transition temperature resulting from enhanced dissociation of ions with an increase in applied electric field.

This book discusses the mechanisms of electric conductivity in various ionic liquid systems (protic, aprotic as well as polymerized ionic liquids). It hence covers the electric properties of ionic liquids and their macromolecular counterpanes, some of the most promising materials for the development of safe electrolytes in modern electrochemical energy devices such as batteries, super-capacitors, fuel cells and dye-sensitized solar cells. Chapter contributions by the experts in the field discuss important findings obtained using broadband dielectric spectroscopy (BDS) and other complementary techniques. The book is an excellent introduction for readers who are new to the field of dielectric properties of ionic conductors, and a helpful guide for every scientist who wants to investigate the interplay between molecular structure and dynamics in ionic conductors by means of dielectric spectroscopy.