Anion Responsive Imidazolium-Based Polymers

Bovine Serum Albumin Effect on Collapsing PNIPAM Chains in Aqueous Solutions: Spin Label and Spin Probe Study

The influence of bovine serum albumin (BSA) on collapsing poly(N-isopropylacrylamide) (PNIPAM) chains was studied with turbidimetry and spin probe and spin label electron paramagnetic resonance spectroscopy. An increased ratio of collapsed chains in aqueous solutions in the narrow temperature region near the LCST appeared in the presence of 2.5-10 wt% BSA. The spin probe EPR data indicate that the inner cavities of the BSA dimers are probably responsive to the capture of small hydrophobic or amphiphilic molecules, such as TEMPO nitroxyl radical. The observed features of the structure and dynamics of inhomogeneities of aqueous PNIPAM-BSA solutions, including their mutual influence on the behavior of the polymer and protein below the LCST, should be considered when developing and investigating PNIPAM-based drug delivery systems.

Polymerized and Colloidal Ionic Liquids─Syntheses and Applications

The breadth and importance of polymerized ionic liquids (PILs) are steadily expanding, and this review updates advances and trends in syntheses, properties, and applications over the past five to six years. We begin with an historical overview of the genesis and growth of the PIL field as a subset of materials science. The genesis of ionic liquids (ILs) over nano to meso length-scales exhibiting 0D, 1D, 2D, and 3D topologies defines colloidal ionic liquids, CILs, which compose a subclass of PILs and provide a synthetic bridge between IL monomers (ILMs) and micro to macro-scale PIL materials. The second focus of this review addresses design and syntheses of ILMs and their polymerization reactions to yield PILs and PIL-based materials. A burgeoning diversity of ILMs reflects increasing use of nonimidazolium nuclei and an expanding use of step-growth chemistries in synthesizing PIL materials. Radical chain polymerization remains a primary method of making PILs and reflects an increasing use of controlled polymerization methods. Step-growth chemistries used in creating some CILs utilize extensive cross-linking. This cross-linking is enabled by incorporating reactive functionalities in CILs and PILs, and some of these CILs and PILs may be viewed as exotic cross-linking agents. The third part of this update focuses upon some advances in key properties, including molecular weight, thermal properties, rheology, ion transport, self-healing, and stimuli-responsiveness. Glass transitions, critical solution temperatures, and liquidity are key thermal properties that tie to PIL rheology and viscoelasticity. These properties in turn modulate mechanical properties and ion transport, which are foundational in increasing applications of PILs. Cross-linking in gelation and ionogels and reversible step-growth chemistries are essential for self-healing PILs. Stimuli-responsiveness distinguishes PILs from many other classes of polymers, and it emphasizes the importance of segmentally controlling and tuning solvation in CILs and PILs. The fourth part of this review addresses development of applications, and the diverse scope of such applications supports the increasing importance of PILs in materials science. Adhesion applications are supported by ionogel properties, especially cross-linking and solvation tunable interactions with adjacent phases. Antimicrobial and antifouling applications are consequences of the cationic nature of PILs. Similarly, emulsion and dispersion applications rely on tunable solvation of functional groups and on how such groups interact with continuous phases and substrates. Catalysis is another significant application, and this is an historical tie between ILs and PILs. This component also provides a connection to diverse and porous carbon phases templated by PILs that are catalysts or serve as supports for catalysts. Devices, including sensors and actuators, also rely on solvation tuning and stimuli-responsiveness that include photo and electrochemical stimuli. We conclude our view of applications with 3D printing. The largest components of these applications are energy related and include developments for supercapacitors, batteries, fuel cells, and solar cells. We conclude with our vision of how PIL development will evolve over the next decade.

Porous Poly(ionic Liquid) Membrane with Metal Nanoparticle Gradient: A Smart Actuator for Visualizing Chemical Reactions

Poly(ionic liquid) (PIL)-based porous membranes are extensively investigated as soft polymer actuators. While PILs have shown significant advancements in membrane fabrication and stabilization of metal nanoparticles (MNPs), research on integrating MNPs into porous membranes to achieve actuation behavior under multiple stimuli is limited. Herein, this work presents a new paradigm for designing a porous PIL-polyacrylic acid (PAA) membrane with a distinct MNP gradient via a top-bottom diffusion approach involving a metal salt precursor solution and NaBH4 as a reducing agent. The strong binding sites provided by PILs, combined with the gradient distribution of -COO- groups across the membrane cross-section, play a significant role in controlling the MNPs' gradient distribution. Interestingly, the MNPs within the membrane display excellent catalytic activity in exothermic reactions such as H2O2 decomposition, dissipating uneven heat that quickly permeates the membrane network. This induces asymmetrical swelling of polymer chains, resulting in rapid membrane bending. Furthermore, such MNP-loaded membrane could serve as a portable test paper for visually monitoring H2O2. This advancement paves the way for the development of intricate smart actuation materials and expands their practical applications in various real-life scenarios.

Advanced Formulations Based on Poly(ionic liquid) Materials for Additive Manufacturing

Innovation in materials specially formulated for additive manufacturing is of great interest and can generate new opportunities for designing cost-effective smart materials for next-generation devices and engineering applications. Nevertheless, advanced molecular and nanostructured systems are frequently not possible to integrate into 3D printable materials, thus limiting their technological transferability. In some cases, this challenge can be overcome using polymeric macromolecules of ionic nature, such as polymeric ionic liquids (PILs). Due to their tuneability, wide variety in molecular composition, and macromolecular architecture, they show a remarkable ability to stabilize molecular and nanostructured materials. The technology resulting from 3D-printable PIL-based formulations represents an untapped array of potential applications, including optoelectronic, antimicrobial, catalysis, photoactive, conductive, and redox applications.

Imidazolium ionic Liquid-Regulated Sub-5-nm Pt(111) with a stable configuration anchored on hollow carbon nanoshells for efficient oxygen reduction

Here, N-doped hollow carbon sphere (NHCS)-supported (111)-plane-engineered sub-5-nm Pt (Pt-NHCS) catalysts regulated precisely by imidazolium ionic liquids were synthesized successfully and used to catalyze oxygen reduction. The (111)-plane engineered Pt nanocrystals with a diameter of 4.5 ± 0.5 nm were homogeneously deposited on the 3-dimensional spherical nanoshells. The resulting Pt nanocrystals anchored on the carbon skeleton exhibit a stable configuration in both alkaline and acid electrolytes with the help of imidazolium cations and pyrolysis. Among all as-prepared catalysts, the optimized Pt-NHCS shows remarkable long-term durability. Specifically, Pt-NHCS maintains 95.3% of the original current density after 10,000 potential cycles, while Pt/C benchmarks exhibit a retention of 78.5%. Accelerated durability test results indicate that Pt-NHCS exhibits a high efficiency of 96 % in comparison with initial current density, while a value of 86% for Pt/C. Density functional theory calculations demonstrate that reactive Pt(111) planes with well-defined Schottky defects and vacancies adsorb and activate oxygen molecule rapidly while desorbing the reaction intermediates.

Complex Coacervation of Polymerized Ionic Liquids in Non-aqueous Solvents

Oppositely charged polymerized ionic liquids (PILs) were used to form complex coacervates in two different organic solvents, 2,2,2-trifluoroethanol (TFE) and hexafluoro-2-propanol (HFIP), and the corresponding phase diagrams were constructed using UV-vis, NMR, and turbidity experiments. While previous studies on complex coacervates have focused almost exclusively on aqueous environments, the use of PILs in the current work enabled studies in solvents with substantially lower dielectric constants (27.0 for TFE, 16.7 for HFIP). The critical salt concentration required to induce complete miscibility was roughly 2-fold larger in HFIP compared with TFE, and two different PIL complexes, solidlike precipitates and liquidlike coacervates, were found in both systems. This study provides insight into the effects of low-dielectric-constant solvents on complex coacervation, which has not been widely studied because of the limited solubility of conventional polyelectrolytes in these media.

Linear Main-Chain 1,2,4-Triazolium Poly(ionic liquid)s: Single-Step Synthesis and Stabilization of Cellulose Nanocrystals

Linear main-chain 1,2,4-triazolium-based poly(ionic liquid)s (PILs) were synthesized in this contribution. The polymerization process is experimentally very simple and involves only a single-step polycondensation of a commercially available monomer in DMSO as solvent at 120 °C. Their thermal stability and solubility were analyzed in terms of different counteranions. Due to the ease of this synthetic route, it was readily applied to graft onto sulfonated cellulose nanocrystals (CNCs) via a one-step in situ polymerization. The as-synthesized PIL@CNC hybrid colloids exhibit adaptive dispensability in water and organic solvents.

1,8-Diamidocarbazoles: an easily tuneable family of fluorescent anion sensors and transporters

The synthesis, structure and anion recognition properties of an extensive, rationally designed series of bisamide derivatives of 1,8-diaminocarbazole and 1,8-diamino-3,6-dichlorocarbazole are described. Despite simple structures and the presence of only three hydrogen bond donors, such compounds are remarkably strong and selective receptors for oxyanions in DMSO + 0.5%H2O. Owing to their carbazole fluorophore, they are also sensitive turn-on fluorescent sensors for H2PO4- and AcO-, with a more than 15-fold increase in fluorescence intensity upon binding. Despite relatively weak chloride affinity, some of the diamidocarbazoles have also been shown, for the first time, to be very active chloride transporters through lipid bilayers. The binding, sensing and transport properties of these receptors can be easily modulated by the usually overlooked variations in the length and degree of branching of their alkyl side arms. Overall, this study demonstrates that the 1,8-diamidocarbazole binding unit is a very promising and synthetically versatile platform for the development of fluorescent sensors and transporters for anions.

Synthesis of a novel graphene-based gold nanocomposite using PVEIM-b-PNIPAM as a stabilizer and its thermosensitivity for the catalytic reduction of 4-nitrophenol

Fabrication of a graphene-based gold nanocomposite using PVEIM-b-PNIPAM as a stabilizer and its thermosensitivity for the reduction of 4-nitrophenol.

Polyoxometalate-coupled MXene nanohybrid via poly(ionic liquid) linkers and its electrode for enhanced supercapacitive performance

MXenes are novel 2D transition metal carbides with metallic conductivity and hydrophilic surfaces, which have highly active 2D surfaces and can act as a promising new type of electrode material; however, their low capacity and irreversible self-restacking limit their practicality and development. This paper presents a novel method for preparing an MXene-polyoxometalate (POM) nanohybrid using poly(ionic liquid) (PIL) as the linker. The electrostatic interactions, chemical structure, and morphology of this nanohybrid are systematically characterized and have indicated that the MXene-PIL-POM nanohybrid provides the uniform distribution of POM nanoparticles on the MXene nanosheets and exhibits excellent electrochemical activity and stability due to the use of PIL as the linker and stabilizer. The prepared MXene-PIL-POM nanohybrid, used as an electrode, displayed a definite improvement in electrochemical performance with the specific capacitance of 384.6 F g-1 at a current density of 1 A g-1, which is about three-fold higher than that of the MXene electrode. The MXene-PIL-POM electrode also achieved a good rate performance (90.5% retention at 10 A g-1) and a long cycling life (91.7% maintenance of specific capacitance at a constant current density of 4 A g-1 after 2000 cycles). The proposed nanohybrid structure capitalizes on the enhancement of the redox reactions of POM through the PIL linkers to facilitate charge transfer and provide efficient ion transfer channels in the nanohybrid.

Porous Polyelectrolytes: The Interplay of Charge and Pores for New Functionalities

The past decade has witnessed rapid advances in porous polyelectrolytes and there is tremendous interest in their synthesis as well as their applications in environmental, energy, biomedicine, and catalysis technologies. Research on porous polyelectrolytes is motivated by the flexible choice of functional organic groups and processing technologies as well as the synergy of the charge and pores spanning length scales from individual polyelectrolyte backbones to their nano-/micro-superstructures. This Review surveys recent progress in porous polyelectrolytes including membranes, particles, scaffolds, and high surface area powders/resins as well as their derivatives. The focus is the interplay between surface chemistry, Columbic interaction, and pore confinement that defines new chemistry and physics in such materials for applications in energy conversion, molecular separation, water purification, sensing/actuation, catalysis, tissue engineering, and nanomedicine.

Frontiers in poly(ionic liquid)s: syntheses and applications

We review recent works on the synthesis and application of poly(ionic liquid)s (PILs). Novel chemical structures, different synthetic strategies and controllable morphologies are introduced as a supplement to PIL systems already reported. The primary properties determining applications, such as ionic conductivity, aqueous solubility, thermodynamic stability and electrochemical/chemical durability, are discussed. Furthermore, the near-term applications of PILs in multiple fields, such as their use in electrochemical energy materials, stimuli-responsive materials, carbon materials, and antimicrobial materials, in catalysis, in sensors, in absorption and in separation materials, as well as several special-interest applications, are described in detail. We also discuss the limitations of PIL applications, efforts to improve PIL physics, and likely future developments.

Stimuli-responsively porating gels by condensation

A polyurethane (PU) resin derived from glycerol and hexamethylene diisocyanate and an imidazolium bromide ionic liquid chain terminator yield a stimuli-responsive resin that reversibly porates as a solvation response.

Anion-Responsive Poly(ionic liquid)s Gating Membranes with Tunable Hydrodynamic Permeability

Novel anion-responsive "intelligent" membranes with functional gates are fabricated by filling polyethersulfone microporous membranes with poly(ionic liquid)s (PILs) gels. The wetting properties of the PILs could be controlled by changing their counteranions (CAs), and thus, the filled PILs gel gates in the membrane pores could spontaneously switch from the "closed" state to the "open" one by recognizing the hydrophilic CAs in the environment and vice versa. As a result, the fluxes of the "intelligent" membranes could be tuned from a very low level (0 mL/m²·mmHg for Cl^-, Br^-, and BF₄^-) to a relatively high one (430 mL/m²·mmHg for TFSI). The anion-responsive gating behavior of the PILs filled membranes is fast, reversible, and reproducible. In addition, the "intelligent" membranes are sensitive to contact time and ion concentrations of the hydrophobic CA species. The proposed anion-responsive "intelligent" membranes are highly attractive for ion-recognizable chemical/biomedical separations and purifications.

Synthesis of porous polymer/tissue paper hybrid membranes for switchable oil/water separation

The unusually broad physical and chemical property window of ionic liquids allows for a wide range of applications, which gives rise to the recent spring-up of ionic liquid-based functional materials. Via solvothermal copolymerization of a monomeric ionic liquid and divinylbenzene in the presence of a tissue paper in autoclave, we fabricated a flexible porous polymer/paper hybrid membrane. The surface areas of the hybrid membranes depend on the weight fraction of the copolymer impregnated inside the tissue paper. The as-prepared hybrid membrane shows controlled surface wettability in terms of ethanol wetting and ethanol removal by harsh drying condition. This unique property provides the hybrid membrane with switchable oil/water separation function, thus of practical values for real life application.

Cubosomes from hierarchical self-assembly of poly(ionic liquid) block copolymers

Cubosomes are micro- and nanoparticles with a bicontinuous cubic two-phase structure, reported for the self-assembly of low molecular weight surfactants, for example, lipids, but rarely formed by polymers. These objects are characterized by a maximum continuous interface and high interface to volume ratio, which makes them promising candidates for efficient adsorbents and host-guest applications. Here we demonstrate self-assembly to nanoscale cuboidal particles with a bicontinuous cubic structure by amphiphilic poly(ionic liquid) diblock copolymers, poly(acrylic acid)-block-poly(4-vinylbenzyl)-3-butyl imidazolium bis(trifluoromethylsulfonyl)imide, in a mixture of tetrahydrofuran and water under optimized conditions. Structure determining parameters include polymer composition and concentration, temperature, and the variation of the solvent mixture. The formation of the cubosomes can be explained by the hierarchical interactions of the constituent components. The lattice structure of the block copolymers can be transferred to the shape of the particle as it is common for atomic and molecular faceted crystals.

Poly(acrylamide-homocysteine thiolactone) as a synthetic platform for the preparation of polymeric ionic liquids by post ring-opening-orthogonal modifications

Post-modification of Poly(Acrylamide-Homocysteine Thiolactone) provides a variety of advanced polymeric materials with different morphologies and structural diversity.

Multiple interaction regulated phase transition behavior of thermo-responsive copolymers containing cationic poly(ionic liquid)s

Schematic illustration of the phase transition mechanism of the P(OEGMA-co-BVIm[SCN]) copolymer.

Properties and applications of designable and photo/redox dual responsive surfactants with the new head group 2-arylazo-imidazolium

2-Arylazo-imidazolium grafted imidazolium surfactants with structural extensibility and reversible responsiveness to photo and electrochemical stimuli for further usage in a sol–gel process.

Preparation of poly(ionic liquid) nanoparticles and their novel application as flocculants for water purification

Amphiphilic poly(ionic liquid) random copolymers that self-assemble into polymeric nanoparticles were prepared. The use of poly(ionic liquid) nanoparticles as flocculants enhanced the evolution rate of the sediment considerably in comparison with the parent polyelectrolytes.

Thiazolium Poly(ionic liquid)s: Synthesis and Application as Binder for Lithium-Ion Batteries

We report a synthetic route to thiazolium-type poly(ionic liquid)s (PILs), which can be applied as a polymeric binder in lithium-ion batteries. The ionic liquid monomers were first synthesized by quaternization reaction of 4-methyl-5-vinyl thiazole with methyl iodide, followed by anion exchange reactions to replace iodide by fluorinated anions to access a liquid state below 100 °C. Subsequently, these monomers bearing thiazolium cations in their structure underwent radical polymerizations in bulk to produce corresponding polymers. The dependence of solution and thermal properties of such monomeric and polymeric materials on the choice of the counteranion was investigated. Finally, the thiazolium-type PIL bearing a bis(trifluoromethanesulfonyl)imide (TFSI) anion was proven to be a high performance binder for lithium-ion battery electrodes.

From polymer latexes to multifunctional liquid marbles

A simple method to prepare multifunctional liquid marbles and dry water with magnetic, color, and fluorescent properties is presented. Multifunctional liquid marbles were prepared by encapsulation of water droplets using flocculated polymer latexes. First, the emulsion polymerization reaction of polystyrene and poly(benzyl methacrylate) was carried out using cheap and commercially available cationic surfactants. Subsequently, flocculation of the latex was provoked by an anion-exchange reaction of the cationic surfactant by the addition of lithium bis(trifluoromethanesulfonyl)imide salt. The flocculated polymer latex was filtered and dried, leading to very hydrophobic micronanoparticulated powders. These powders showed a great ability to stabilize the air/water interface. Stable liquid marbles were obtained by rolling water droplets onto the hydrophobic powders previously prepared. The use of very small polystyrene nanoparticles led us to the preparation of very stable and the biggest known liquid marbles up to 2.5 mL of water. Furthermore, the introduction of fluorescent comonomer dyes into the polymer powders allowed us to obtain new morphological images and new knowledge about the structure of liquid marbles by confocal microscopy. Furthermore, the introduction of magnetic nanoparticles into the polymer latex led to magnetic responsive liquid marbles, where the iron oxide nanoparticles are protected within a polymer. Altogether this method represents an accessible and general platform for the preparation of multifunctional liquid marbles and dry water, which may contribute to extending of their actual range of applications.

The evolution of cyclopropenium ions into functional polyelectrolytes

Versatile polyelectrolytes with tunable physical properties have the potential to be transformative in applications such as energy storage, fuel cells and various electronic devices. Among the types of materials available for these applications, nanostructured cationic block copolyelectrolytes offer mechanical integrity and well-defined conducting paths for ionic transport. To date, most cationic polyelectrolytes bear charge formally localized on heteroatoms and lack broad modularity to tune their physical properties. To overcome these challenges, we describe herein the development of a new class of functional polyelectrolytes based on the aromatic cyclopropenium ion. We demonstrate the facile synthesis of a series of polymers and nanoparticles based on monomeric cyclopropenium building blocks incorporating various functional groups that affect physical properties. The materials exhibit high ionic conductivity and thermal stability due to the nature of the cationic moieties, thus rendering this class of new materials as an attractive alternative to develop ion-conducting membranes.

Preparation of anion-exchangeable polymer vesicles through the self-assembly of hyperbranched polymeric ionic liquids

Anion-exchangeable polymer vesicles including pH-indicative and protein-coated vesicles were prepared through the self-assembly of a hyperbranched polymeric ionic liquid.

Aqueous graphene dispersions-optical properties and stimuli-responsive phase transfer

We demonstrate essentially complete exfoliation of graphene aggregates in water at concentrations up to 5% by weight (166-fold greater than previous high concentration report) using recently developed triblock copolymers and copolymeric nanolatexes based on a reactive ionic liquid acrylate surfactant. We demonstrate that the visible absorption coefficient in aqueous dispersion, 48.9 ± 1.3 cm(2)/mg at 500 nm, is about twice that currently accepted, and we show that this value is a greatest lower bound to extant macroscopic single sheet optical studies of graphene when one considers both fine structure constant and excitonic mechanisms of visible absorption. We also show that dilute and concentrated graphene dispersions are rheo-optical fluids that exhibit an isotropic to nematic transition upon application of a shear field, and we demonstrate stimuli-responsive phase transfer.