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.

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 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.

Polymerized ionic liquids are an emerging class of functional materials with ionic liquid moieties covalently attached to a polymer backbone. As such, they synergistically combine the structural hierarchy of polymers with the versatile physicochemical properties of ionic liquids. Unlike other ion-containing polymers that are typically constrained to high glass transition temperatures, polymerized ionic liquids can exhibit low glass transition temperatures due to weak electrostatic interactions even at high charge fractions. Promising applications relevant to electrochemical energy conversion and CO2 capture and sequestration have been demonstrated for polymerized ionic liquids, but a molecular design strategy that allows for elucidation of their structure-property relationships is yet to be developed. A combination of anionic polymerization, click chemistry, and ion metathesis allows for fine and independent control over polymer properties including the number of repeat units, fraction of ionic liquid moieties, composition, and architecture. This strategy has been exploited to elucidate the effect of lamellar domain spacing on the ionic conductivity of block copolymers based on hydrated protic polymerized ionic liquids. The conductivity relationship demonstrated in this study suggests that a mechanically robust material can be designed without compromising its ability to transport ions. The vast set of ion pair combinations in polymerized liquids provides a unique opportunity to develop functional materials where properties can be controlled with subtle changes in molecular structure via ion metathesis. We illustrate the case of a polymerized ionic liquid that combines the low toxicity and macromolecular dimensions of poly(ethylene glycol) with the magnetic functionality of ion pairs containing iron(III). This material can yield novel theranostic agents with controlled residence time within the human body, and paramagnetic functionality to enhance 1H nuclei relaxation rate required for medical imaging. Finally, the molecular design strategy is expanded to incorporate ion pairs based on metal-ligand coordination bonds between cations and imidazole moieties tethered to the polymer backbone. This illustrates a general approach for using chelating polymers with appropriate metal-ligand interactions to design high conductivity and tunable modulus polymer electrolytes.

This book includes manuscripts from well-recognized international research groups that have taken different approaches to using ionic liquids in a variety of polymer applications. The chapters on polymer synthesis cover traditional free radical polymerizations, which have been shown to progress rapidly and yield high molecular weight polymers, and reverse atom transfer polymerizations. The ability to tune molecular weights and synthesize block copolymers has been attributed to long free radical lifetimes in ionic liquids. Other chapters cover a variety of uses for ionic liquids in polymer processing, designing specific material properties, and creating novel composites, such as ion gels and ionic liquid-carbon nanotube constructs. This book represents a new and exciting field in polymer chemistry and physics, and is growing rapidly as more fundamental knowledge of ionic liquids is uncovered.