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

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.

Polymerized ionic liquids (PILs) show potential to be used as new water-free polyelectrolyte-based electrorheological (ER) material. To direct ER material design at the molecular level, unveiling structure-property relationships is essential. While a few studies compare the mobile ions in PILs there is still a limited understanding of how the structure of tethered counterions on backbone influences ER property. In this study, three PILs with same mobile anions but different tethered countercations (e.g., poly(dimethyldiallylammonium) P[DADMA]+, poly(benzylethyl) trimethylammonium P[VBTMA]+, and poly(1-ethyl-4-vinylimidazolium hexafluorophosphate) P[C2VIm]+) are prepared and the influence of tethered countercations on the ER property of PILs is investigated. It shows that among these PILs, P[DADMA]+ PILs have the strongest ER property and P[C2VIm]+ PILs have the weakest one. By combining dielectric spectra analysis with DFT calculation and activation energy measurement, it can clarify that the influence of tethered counterions on ER property is mainly associated with ion-pair interaction energy that is affecting ionic conductivity and interfacial polarization induced by ion motion. P[DADMA]+ has the smallest ion-pair interaction energy with mobile ions, which can result in the highest ionic conductivity and the fastest interfacial polarization rate for its strongest ER property.

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.

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.

Influence of alkyl spacer length on ion transport, polarization and electro-responsive electrorheological effect of self-crosslinked poly(ionic liquid)s

There have been many reports on electrorheological (ER)1–4 suspensions because of their remarkable ER effect. Besides these two-phase systems, some one-phase system or homogeneous ER fluids5–14, such as polymeric liquids, have been developed. The homogeneous ER fluids are free from the problems seen in suspensions due to dispersed particles, e.g., sedimentation, aggregation, friction, which reduce the ER effect. We have been studying ER effects in polymeric liquids to establish a model for understanding the mechanism of the ER effects in such homogeneous systems6,12–14. Among the homogeneous ER fluids, polymers with flexible side chain connected with polar mesogenic group have a large ER effect8, 9. At present, the mechanism of the ER effect in these liquid crystal polymers (LCP) has been interpreted as the inhibition of the slipping between mesogenic domains by the flexible chains connecting them under an electric field. Detailed rheological examinations are necessary for further understanding of the mechanism.

Synthesis and properties of polymerized ionic liquids

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

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

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.

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. 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. In addition, the impact of morphology on charge transport is not considered within the framework of these theories. 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 the impact of morphology on charge transport and structural dynamics in systematic series of 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. In addition, the strong correlation observed between ionic conductivity from dielectric experiments and morphologies from scattering and computational studies will be discussed.

Enhancing the performance of electrorheological fluids by structure design

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.

This paper reports the preparation of chitin/cellulose films compatibilized with polymeric ionic liquids. In-situ (co)polymerization of polymerizable ionic liquids, 1-(3-methacryloyloxypropyl)-3-vinylimidazolium bromide (1) and 1-methyl-3-vinylbenzylimidazolium chloride (3), was carried out in the presence of a radical initiator, AIBN, in the chitin/cellulose solution with ionic liquid solvents (1-butyl-3-methylimidazolium acetate and chloride, BMIMOAc and BMIMCl, respectively), followed by the appropriate procedure to give the desired films. The presence of the polymeric ionic liquid in the film was confirmed by the IR measurement. The powder X-ray diffraction analysis suggested that crystalline structures of the polysaccharides were largely disrupted in the film, as same as that of a chitin/cellulose film prepared by the AMIMOAc/BMIMCl system. These results were different from the XRD result of a chitin/cellulose film prepared by the 1-allyl-3-methylimidazolium bromide/BMIMCl system reported in our previous study, in which some crystalline structures were still remained in the film. Furthermore, the mechanical properties of the present films were evaluated by tensile testing, which were affected by the molar ratios of the polymeric ionic liquids to the polysaccharides and the compositional ratios of the two units 1 and 3.

VRFBs based on benzotriazole grafted polybenzimidazole / polymeric ionic liquid with high ion selectivity