(Invited) Ion Transport in Polymerized Ionic Liquids: Structure-Morphology-Property Relationships

Polymerized ionic liquids (PolyILs) are a novel class of functional polymers that combine the unique physicochemical properties of molecular ionic liquids with the outstanding mechanical characteristics of polymers [1,2]. This special mix of features might help to circumvent the key limitations of low molecular weight ionic liquids, namely, leakage and poor mechanical properties while utilizing their outstanding characteristics such as low vapor pressures, wide liquidus ranges, high thermal stability, high ionic conductivity, and wide electrochemical windows. PolyILs have shown remarkable advantages when employed in electrochemical devices such as dye-sensitized solar cells, lithium batteries, actuators, field-effect transistors, light emitting electrochemical cells, and electrochromic devices, among others. Despite their promising prospects as ideal polymer electrolytes, the role of molecular structure, morphology, and polymer dynamics on charge transport in PolyILs remains poorly understood. According to classical theories, the self-diffusion and ion transport in electrolytes are controlled by structural relaxation. These approaches predict similar temperature dependence for the dc conductivity and structural dynamics. Although this prediction has been shown to hold reasonably well for low molecular weight aprotic ionic liquids, it fails for PolyILs [2,3]. In addition, the impact of morphology charge transport is not considered within the framework of these theories. The first part of this talk will focus on new insights obtained from experimental studies employing broadband dielectric spectroscopy, temperature-modulated differential scanning calorimetry, rheology, and scattering techniques to elucidate charge transport and structural dynamics in a systematic series of bulk polymerized ammonium- and imidazolium- based ionic liquids. Detailed analyses reveal strong decoupling of these processes in the PolyILs, implying the limitation of the classical theories in describing charge transport and molecular dynamics in these materials, in contrast to low molecular weight systems (4,5). In addition, the strong correlation observed between ionic conductivity from dielectric experiments and morphologies from scattering studies will be reviewed. In the second part of this talk, our recent results from a new approach to dielectric experiments yielding details about ion dynamics in ultrathin films of polymerized ionic liquids down to sub-5nm film thicknesses will be discussed. While the characteristic charge transport rates remain bulk-like down to about 5 nm film thicknesses, ionic-liquid/substrate interactions play an increasingly significant role in determining ion dynamics in confined polymerized ionic liquids (5). These results will be considered within the context of recent models of charge transport and polymer dynamics under confinement. References 1) Mecerreyes, D. Progress in Polymer Science 2011, 36, 1629. 2) Sangoro, J. R. and Kremer, F. Accounts of Chemical Research 2012, 45, 525 3) Sangoro, J. R. et al., Soft Matter 2014, 10, 3536. 4) Wojnarowska, Z. et al., Macromolecules 2015, 48 (23), 8660-8666. 5) Heres, M. F. et al., Submitted.

Antimicrobial resistance has become a serious threat to global health. New antimicrobials are thus urgently needed. Ionic liquids (ILs), salts consisting of organic cations and anions with melting points less than 100°C, have been recently found to be promising in antimicrobial field as they may disrupt the bacterial wall and membrane and consequently lead to cell leakage and death. Different types of antimicrobial ILs are introduced in the review, including cationic, polymeric, and anionic ILs. Being the main type of the antimicrobial ILs, the review focuses on the structure and the antimicrobial mechanisms of cationic ILs. The quantitative structure-activity relationship (QSAR) models of the cationic ILs are also included. Increase in alkyl chain length and lipophilicity is beneficial to increase the antimicrobial effects of cationic ILs. Polymeric ILs are homopolymers of monomer ILs or copolymers of ILs and other monomers. They have great potential in the field of antibiotics as they provide stronger antimicrobial effects than the sum of the monomer ILs. Anionic ILs are composed of existing anionic antibiotics and organic cations, being capable to enhance the solubility and bioavailability of the original form. Nonetheless, the medical application of antimicrobial ILs is limited by the toxicity. The structural optimization aided by QSAR model and combination with existing antibiotics may provide a solution to this problem and expand the application range of ILs in antimicrobial field.

Owing to their robust and tunable properties compared to molecular compounds, ionic liquids and their high molecular weight counterparts, polymeric ionic liquids, have provided suitable compounds for the development of smart materials with high physical and chemical stability and strongly stimulus-responsive characteristics. By functionalizing ionic liquids themselves or incorporating ionic liquids into traditional materials, many new kinds of stimuli-responsive materials have been developed. In this chapter, we specifically focus on the recent advances in electro-responsive electrorheological smart fluids with ionic liquids and polymeric ionic liquids as either active components or additives. The goal is to highlight the potential of incorporating ionic liquids into traditional electrorheological materials and using polymeric ionic liquids as new electrorheological active materials to overcome the problems of present electrorheological fluids for real applications.

Enhanced electrorheological effectiveness and temperature effect of suspensions based on poly(ionic liquid)s neutralized with mixed counterions

The aim of this study was to develop ionic liquid (IL) polymer materials incorporating enzymes that can be used as active, stable and reusable biocatalysts. To this goal, Candida rugosa lipase has been microencapsulated in surfactant aggregates formed in an IL monomer or the solution of an IL monomer/IL and then incorporated into polymer frameworks through the free radical polymerization of an IL (1-vinyl-3-ethylimidazolium bis(trifluoromethyl-sulfonyl) amide) ([veim][Tf(2)N]). The activity, stability and reusability of such IL polymer materials containing lipase were evaluated using lipase-catalyzed hydrolysis of p-nitrophenyl butyrate (p-PNB) as a model reaction. Lipase encapsulated within ionic liquid polymer materials remained active and exhibited excellent stability in aqueous solutions. More importantly, these biopolymer materials retained most of their activity after five reaction cycles, in which biopolymers were recovered from the reaction mixture simply by centrifugation. This study promulgates a direction toward the design of IL - an interesting class of tunable and designable solvents - based polymer materials containing biomolecules via a combination of polymer and supramolecular chemistry for diverse applications.

Synthesis and properties of polymerized ionic liquids

Preparation of cellulose-polymerized ionic liquid composite by in-situ polymerization of polymerizable ionic liquid in cellulose-dissolving solution

Understanding the connection between the molecular structureofionic liquids and their properties is of paramount importance forpractical applications. However, this connection can only be establishedif a broad range of physicochemical properties on different lengthand time scales is already available. Even then, the interpretationof the results often remains ambiguous due to the natural limits ofexperimental approaches. Here we use fast-field cycling (FFC) to accessboth translational and rotational dynamics of ionic liquids. Thesecombined with a comprehensive physicochemical characterization andMD simulations provide a toolkit to give insight into the mechanismsof molecular mechanics. The FFC results are consistent with the computersimulation and conventional physicochemical approaches. We show thatcurling of the side chains around the positively charged cationiccore is essential for the properties of ether-functionalized ionicliquids, and we demonstrate that neither geometry nor polarity aloneare sufficient to explain the macroscopic properties.

This chapter provides an overview of a novel family of ionic liquids, redox-active ionic liquids and redox polymer ionic liquids. The flexible design of this new family of ionic liquids allows for the tuning of various properties. Then, these compounds can act as multifunctional materials for diverse applications. In this chapter, different approaches and procedures for immobilizing redox-active ionic liquids, from thin layers to polymers, are mentioned and reviewed. Importantly, polymer ionic liquids have largely contributed to recent advances in polymer sciences and are becoming key materials in different fields, such as energy storage (batteries, supercapacitors), energy conversion (actuators), and information processing (sensors).

We report a molecular dynamics study of the structure and single-particle dynamics of mixtures of a protic (ethylammonium nitrate) and an aprotic (1-butyl-3-methylimidazolium hexaflurophosphate [BMIM][PF6]) room-temperature ionic liquids doped with magnesium and calcium salts with a common anion at 298.15 K and 1 atm. The solvation of these divalent cations in dense ionic environments is analyzed by means of apparent molar volumes of the mixtures, radial distribution functions, and coordination numbers. For the protic mixtures, the effect of salt concentration on the network of hydrogen bonds is also considered. Moreover, single-particle dynamics of the salt cations is studied by means of their velocity autocorrelation functions and vibrational densities of states, explicitly analyzing the influence of salt concentration, and cation charge and mass on these magnitudes. The effect of the valency of the salt cation on these properties is considered comparing the results with those for the corresponding mixtures with lithium salts. We found that the main structural and dynamic features of the local solvation of divalent cations in ionic liquids are similar to those of monovalent salts, with cations being localized in the polar nanoregions of the bulk mixture coordinated in monodentate and bidentate coordination modes by the [NO3](-) and [PF6](-) anions. However, stronger electrostatic correlations of these polar nanoregions than in mixtures with salts with monovalent cations are found. The vibrational modes of the ionic liquid (IL) are seen to be scarcely affected by the addition of the salt, and the effect of mass and charge on the vibrational densities of states of the dissolved cations is reported. Cation mass is seen to exert a deeper influence than charge on the low-frequency vibrational spectra, giving a red shift of the vibrational modes and a virtual suppression of the higher energy vibrational modes for the heavier Ca(2+) cations. No qualitative difference with monovalent cations was found in what solvation is concerned, which suggests that no enhanced reduction of the mobility of these cations and their complexes in ILs respective to those of monovalent cations is to be expected.

Analysis of beer volatiles by polymeric imidazolium-solid phase microextraction coatings: Synthesis and characterization of polymeric imidazolium ionic liquids

Kinetics of radical polymerization in ionic liquids

The synthesis of polymer ionic liquids and ionene-type ionic liquids has been optimized through the implementation of a rigorous scientific and methodical approach. The feasibility of utilizing an integrated "polymer–monomer" strategy for synthesizing polymer ionic liquids has been demonstrated. The concentration-dependent viscosity of ionene-type polymer ionic liquids in solutions was analyzed, and the influence of their chemical nature was elucidated. Practical recommendations have been developed to address the scientific and applied challenges associated with creating new ionene-type polymer ionic liquids that exhibit high ionic conductivity while maintaining a liquid state over a wide temperature range. These findings aim to solve pressing issues in chemical technology.

A set of new experimental data was obtained regarding the influence of the structure of dimer ionene ionic liquids on their physical and chemical properties, which is the basis of the methodology for the synthesis of polymer ionene ionic liquids. It was established that the introduction of allyl and -hydroxyethyl groups into the quaternary nitrogen atom, the presence of a dibenzyl fragment at the cationic center and alkylaromatic radicals permit obtaining polymeric ionic liquids of the ionene type with a high level of ionic conductivity at a low glass transition temperature. Newly synthesized polymeric ionic liquids and ionene ionic liquids based on 1,2-epoxy-4,7-dioxononen-8 and tetrahydro-1,4-oxazine derivatives with an ionic conductivity of ~10–1–10–4 S cm–1 with glass transition temperature range of –1400С to –160С exhibited five to six orders of magnitude higher ionic conductivity as compared with known analogues. Recommendations for solving the problem of developing polymeric ionic liquids and ionene ionic liquids exhibiting high ionic conductivity while maintaining their liquid state in a wide temperature range have been developed.

The aza-Michael reaction is a fundamental transformation for carbon-nitrogen bond formation, providing efficient access to β-amino carbonyl compounds, nitriles, and related nitrogen-containing building blocks of broad importance in medicinal chemistry and organic synthesis. Over the past two decades, ionic liquids (ILs) have attracted considerable attention as alternative reaction media, promoters, and catalysts for aza-Michael reactions, owing to their distinctive physicochemical properties and tunable structures. This review presents a comprehensive and critical overview of ionic-liquid-mediated aza-Michael reactions, emphasizing the evolution of IL design from early imidazolium-based systems to modern task-specific, supported, and bio-derived ionic liquids. Conventional room-temperature ionic liquids are discussed as non-innocent solvents capable of stabilizing charged intermediates and enhancing electrophilicity, thereby enabling catalyst-free or metal-assisted aza-Michael additions. Subsequent sections focus on task-specific ionic liquids incorporating Brønsted acidic, basic, hydrogen-bond-donating, or bifunctional motifs, highlighting how rational structural design translates into improved activity, selectivity, and substrate scope. Particular attention is devoted to guanidine-, DABCO-, and DBU-based ionic liquids, where mechanistic studies reveal cooperative activation modes rather than simple acid-base catalysis. Recent advances in supported and polymeric ionic liquids are also reviewed, demonstrating effective strategies to combine IL-like reactivity with enhanced recyclability and operational simplicity. Overall, this review clarifies the diverse roles of ionic liquids in aza-Michael chemistry and outlines current challenges and future perspectives toward more sustainable and efficient C-N bond-forming methodologies.