Poly(ionic liquid)s: An update

Electric-Field-Induced Gradient Ionogels for Highly Sensitive, Broad-Range-Response, and Freeze/Heat-Resistant Ionic Fingers

Human fingers exhibit both high sensitivity and wide tactile range. The finger skin structures are designed to display gradient microstructures and compressibility. Inspired by the gradient mechanical Young's modulus distribution, an electric-field-induced cationic crosslinker migration strategy is demonstrated to prepare gradient ionogels. Due to the gradient of the crosslinkers, the ionogels exhibit more than four orders of magnitude difference between the anode and the cathode side, enabling gradient ionogel-based flexible iontronic sensors having high-sensitivity and broader-range detection (from 3 × 10² to 2.5 × 10⁶  Pa) simultaneously. Moreover, owing to the remarkable properties of the gradient ionogels, the flexible iontronic sensors also show good long-time stability (even after 10 000 cycles loadings) and excellent performance over a wide temperature range (from -108 to 300 °C). The flexible iontronic sensors are further integrated on soft grips, exhibiting remarkable performance under various conditions. These attractive features demonstrate that gradient ionogels will be promising candidates for smart sensor applications in complex and extreme conditions.

On-line separation/analysis of Rhodamine B dye based on a solid-phase extraction high performance liquid chromatography self-designed device

A special self-designed device based on poly-1-vinyl-3-pentylimidazole hexafluorophosphate (PILs-C5) solid-phase extraction and high performance liquid chromatography (HPLC) is proposed as a novel method for the on-line separation and analysis of Rhodamine B (RhB) dye. Single factor experiment design and orthogonal experiment design were used to optimize the experimental parameters, such as pH, the amount of PILs-C5, sample volume, flow rate, eluent type, eluent concentration, eluent volume, and the flow rate of eluent. Under the optimized conditions, the linear range was 0.02-2.4 μg mL-1, with the correlation coefficients (R 2) of 0.997. The limit of detection (LOD) and limit of quantification (LOQ) were 0.004 μg mL-1 and 0.02 μg mL-1, respectively. The extraction capacity was 6.22 mg g-1, and enrichment ratio was 15. The extraction mechanism and the post-treatment method of PILs-C5 were also studied. This method was applied to analyze RhB in a wide variety of real samples with satisfactory results.

Dual-Cationic Poly(ionic liquid)s Carrying 1,2,4-Triazolium and Imidazolium Moieties: Synthesis and Formation of a Single-Component Porous Membrane

Both imidazolium and 1,2,4-triazolium cations are important functional moieties widely incorporated as building blocks in poly(ionic liquid)s (PILs). In a classical model, a PIL usually contains either imidazolium or 1,2,4-triazolium in its repeating unit. Herein, via exploiting the slight reactivity difference of alkyl bromide with imidazole and 1,2,4-triazole at room temperature, we synthesized dual-cationic PIL homopolymers carrying both imidazolium and 1,2,4-triazolium moieties in the same repeating unit, that is, an asymmetrically dicationic unit. We investigated their fundamental properties, for example, thermal stability and solubility, as well as their unique function in forming supramolecular porous membranes via a water-initiated phase-separation and cross-linking process. With such knowledge, we identified a water-based fabricate strategy toward air-stable porous membranes from single-component PILs. This study will enrich the design tools and chemical structure library of PILs and expand their application spectrum.

Efficient Photocatalytic Degradation of Gaseous Benzene and Toluene over Novel Hybrid PIL@TiO2/m-GO Composites

In this work, the PIL (poly ionic liquid)@TiO2 composite was designed with two polymerized ionic liquid concentrations (low and high) and evaluated for pollutant degradation activity for benzene and toluene. The results showed that PIL (low)@TiO2 composite was more active than PIL (high)@TiO2 composites. The photodegradation rate of benzene and toluene pollutants by PIL (low)@TiO2 and PIL (high)@TiO2 composites was obtained as 86% and 74%, and 59% and 46%, respectively, under optimized conditions. The bandgap of TiO2 was markedly lowered (3.2 eV to 2.2 eV) due to the formation of PIL (low)@TiO2 composite. Besides, graphene oxide (GO) was used to grow the nano-photocatalysts’ specific surface area. The as-synthesized PIL (low)@TiO2@GO composite showed higher efficiency for benzene and toluene degradation which corresponds to 91% and 83%, respectively. The resultant novel hybrid photocatalyst (PIL@TiO2/m-GO) was prepared and appropriately characterized for their microstructural, morphology, and catalytic properties. Among the studied photocatalysts, the PIL (low)@TiO2@m-GO composite exhibits the highest activity in the degradation of benzene (97%) and toluene (97%). The ultimate bandgap of the composite reached 2.1 eV. Our results showed that the as-prepared composites hold an essential role for future considerations over organic pollutants.

Quantitative Evidence of Mobile Ion Hopping in Polymerized Ionic Liquids

Atomistic molecular dynamics simulations were performed, and an extensive set of analyses were undertaken to understand the ion transport mechanism in the polymerized ionic liquid poly(C₂VIm)Tf₂N. The ion hopping events were investigated at different time scales. Ion hopping was examined by monitoring the instantaneous cation-anion association and dissociation. Ion diffusion was subsequently evaluated with correlation functions and the calculation of relaxation times at different time scales. Dynamical heterogeneity in the mobility of the ions was observed with only a small portion of the anions classified as fast mobile ions. The mobile ions were characterized as the ones traveling farther than a certain distance during a characteristic period, which was much longer than the time scale of the instant ion pair dissociation. Effective hopping of the mobile ions contributed to the diffusivity which was dominated by interchain hopping and generally facilitated with five associating cations from two different polymer chains. Mobile anions had relatively fewer associating cations from more associating chains than immobile anions. The stringlike cooperative motion was observed in the mobile anions. The string length was determined to decrease with increasing temperature. These findings provided an in-depth understanding of the ion transport in polymerized ionic liquids and important information for the rational design of novel materials.

Effects of repeat unit charge density on the physical and electrochemical properties of novel heterocationic poly(ionic liquid)s

The higher the charge density of PILs the higher their T_g and the lower their conductivity; the best conductivity (1.8 × 10⁻⁵ S cm⁻¹ at 25 °C): PILs with triazolium cations; the best cathodic stability (−0.4 V vs. Li⁺/Li at 70 °C): PILs with mixed type cations.

Ionic liquid-derived polyelectrolyte promoting the biphasic condensation of immiscible reactants at moderate temperature

Both an ionic liquid catalyst (ILC1) and a related cross-linked polyelectrolyte effectively promote the biphasic condensation of glycerol with oleic acid at moderate temperature.

Poly(ionic liquid)s with branched side chains: polymer design for breaking the conventional record of ionic conductivity

Poly(ionic liquid)s with branched side chains can break the conventional record of ionic conductivity of single-ion conductors.

Poly(ionic liquid)s with superior swelling and enrichment properties in solvents

The molar swelling ratio and enrichment factor of poly(ionic liquid)s were linearly positively correlated with the Hansen solubility parameter of the solvent and the difference between the Hansen solubility parameters of mixed solvents, respectively.

All poly(ionic liquid) block copolymer nanoparticles from antagonistic isomeric macromolecular blocks via aqueous RAFT polymerization-induced self-assembly

All-poly(ionic liquid) block copolymer nanoparticles are prepared by aqueous RAFT PISA using a couple of isomeric ionic liquid monomers leading to macromolecular building blocks with antagonistic solution behavior in water.

Cross-linked, porous imidazolium-based poly(ionic liquid)s for CO2 capture and utilisation

A series of micro/meso porous imidazolium poly(ionic liquid)s for CO2 capture and utilization is reported. They show moderate sorption capacity under RTP conditions, and good catalytic activity towards the cycloaddition of CO2 and epoxides to synthesize cyclic carbonates.

Critical Role of Ion Exchange Conditions on the Properties of Network Ionic Polymers

Ionic polymers are important in a wide range of applications and can exhibit widely different properties depending on the ionic species. In the case of single ion conducting polymers, where one charge is attached to the backbone or as a side group, ion exchange is performed to control the mobile species. While the conditions are often specified, the final ion content is not always quantified, and there are no clear criteria for what concentration of salt is needed in the exchange. A series of ammonium network ionic polymers with different precise carbon spacers (C4-C7) between ionic junctions were synthesized as model systems to understand how the ion exchange conditions impact the resultant polymer properties. The initial networks with free bromide anions were exchanged with 1.5, 3, or 10 equiv of lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt in solution. For networks with seven carbons between cross-links, increasing the LiTFSI concentration led to an increase in ion exchange efficiency from 83.6 to 97.6 mol %. At the highest conversion, the C7 network showed a 4 °C decrease in glass transition temperature (T_g), a 50 °C increase in degradation temperature, 12-fold lower water uptake from air, and a greater than 10-fold increase in conductivity at 90 °C. These results illustrate that properties such as T_g are less sensitive to residual ion impurities, whereas the conductivity is highly dependent on the final exchange conversion.

The influence of the polymerization approach on the catalytic performance of novel porous poly (ionic liquid)s for green synthesis of pharmaceutical spiro-4-thiazolidinones

Although poly (ionic liquids) (PILs) have attracted great research interest owing to their various applications, the performance of nanoporous PILs has been rarely developed in the catalysis field. To this end, a micro–mesoporous PIL with acid–base bifunctional active sites was designed and fabricated by two different polymerization protocols including hydrothermal and classical precipitation polymerization in this paper. Based on our observations, hydrothermal conditions (high temperature and pressure) enabled the proposed sonocatalyst to possess a great porous structure with a high specific surface area (S_BET: 315 m² g⁻¹) and thermal stability (around 450 °C for 45% weight loss) through strengthening cross-linking. In a comparative study, the preferred nanoporous PIL was selected and utilized as the sonocatalyst in a multicomponent reaction of isatins, primary amines, and thioglycolic acid. In the following, a variety of new and known pharmaceutical spiro-4-thiazolidinone derivatives were synthesized at room temperature and obtained excellent yields (>90%) within short reaction times (4–12 min) owing to the substantial synergistic effect between ultrasound irradiation and magnetically separable catalyst.

Sustainable synthesize of a new mesoporous poly (ionic liquid) as acid–base bifunctional catalyst for environmental being preparation of monospiro derivatives has been developed.

Functions of Ionic Liquids in Preparing Membranes for Liquid Separations: A Review

Membranes are widely used for liquid separations such as removing solute components from solvents or liquid/liquid separations. Due to negligible vapor pressure, adjustable physical properties, and thermal stability, the application of ionic liquids (ILs) has been extended to fabricating a myriad of membranes for liquid separations. A comprehensive overview of the recent developments in ILs in fabricating membranes for liquid separations is highlighted in this review article. Four major functions of ILs are discussed in detail, including their usage as (i) raw membrane materials, (ii) physical additives, (iii) chemical modifiers, and (iv) solvents. Meanwhile, the applications of IL assisted membranes are discussed, highlighting the issues, challenges, and future perspectives of these IL assisted membranes in liquid separations.

Design of poly ionic liquids modified cotton fabric with ion species-triggered bidirectional oil-water separation performance

A novel ion species-responsive oil-water separation material was designed: poly ionic liquid (PIL) was carried on the graphene oxide (GO) by free radical polymerization, then the PIL modified GO sheets (GO-PIL) were coated on cotton fabric (CF). The wettability of the obtained GO-PIL coated CF (GO-PIL@CF) could be switched between hydrophilic and hydrophobic state with the exchange of different types of counteranions. Water contact angle of the GO-PIL@CF could be switched between 0 to about 145°; and correspondingly the underwater oil contact angle would change between about 148 to 0°. Because of the switchable wettability, the GO-PIL@CF could selectively separate water or oil from the oil-water mixtures. Meanwhile, due to the loose fibrous structure, the GO-PIL@CF showed relatively high permeate fluxes; in the hydrophilic state the water flux was about 36000 L/m²h, while in the hydrophobic state the fluxes for the low-density oils (n-hexane and toluene) were about 59,000 and 65000 L/m²h, respectively. Consequently, the separation processes could be completed simply by gravity. In addition, because of the soft and flexible mechanical property, the GO-PIL@CF could serve as wrappage of traditional absorbents and be applied directly as absorbent to remove water or oil selectively from their mixtures.

Accelerating Crystallization of Open Organic Materials by Poly(ionic liquid)s

The capability to significantly shorten the synthetic period of a broad spectrum of open organic materials presents an enticing prospect for materials processing and applications. Herein we discovered 1,2,4‐triazolium poly(ionic liquid)s (PILs) could serve as a universal additive to accelerate by at least one order of magnitude the growth rate of representative imine‐linked crystalline open organics, including organic cages, covalent organic frameworks (COFs), and macrocycles. This phenomenon results from the active C5‐protons in poly(1,2,4‐triazolium)s that catalyze the formation of imine bonds, and the simultaneous salting‐out effect (induced precipitation by decreasing solubility) that PILs exert on these crystallizing species.

Cation Effect in the Corrosion Inhibition Properties of Coumarate Ionic Liquids and Acrylic UV-Coatings

Chromate free corrosion inhibitors are searched for to mitigate the economic loss caused by mid-steel corrosion. Here, we show metal-free organic inhibitors having free coumarate anions that can be used either as direct corrosion inhibitors or incorporated into a polymer coating obtained by UV-curing. Four different ionic liquid monomers and polymer coatings with hexoxycoumarate anion and different polymerizable counter cations were investigated. Potentiodynamic polarization, electrochemical impedance spectroscopy, and surface analyses have verified their corrosion inhibition performance on a mild steel AS1020 surface. In the case of the coumarate ionic liquid monomers, the most promising inhibitor is the one coupled with the ammonium cation, showing an inhibition efficiency of 99.1% in solution followed by the imidazolium, pyridinium, and anilinium. Next, the ionic liquid monomers were covalently integrated into an acrylic polymer coating by UV-photopolymerization. In this case, the barrier effect of the polymer coating is combined with the corrosion inhibitor effect of the pendant coumarate anion. Here, the best polymer coatings are those containing 20% imidazolium and pyridinium cations, presenting a greater impedance in the EIS (Electrochemical Impedance Spectroscopy) measurements and less evidence of corrosion in the scribe tests. This article shows that the cationic moiety of coumarate based ionic liquids and poly(ionic liquid)s has a significant effect on their excellent corrosion inhibition properties for a mild steel surface exposed to aqueous chloride solutions.

UV-Polymerized Vinylimidazolium Ionic Liquids for Permselective Membranes

Ionic liquids are highly charged compounds with increasing applications in material science. A universal approach to synthesize free-standing, vinylalkylimidazolium bromide-containing membranes with an adjustable thickness is presented. By the variation of alkyl side chains, membrane characteristics such as flux and mechanical properties can be adjusted. The simultaneous use of different ionic liquids (ILs) in the synthesis can also improve the membrane properties. In separation application, these charged materials allowed us to retain charged sugars, such as calcium gluconate, by up to 95%, while similar neutral compounds such as glucose passed the membrane. An analysis of the surface conditions using atomic force microscopy (AFM) confirmed the experimental data and explains the decreasing permeance and increased retention of the charged sugars.

Polymeric Ionic Liquids Derived from L-Valine for the Preparation of Highly Selective Silica-Supported Stationary Phases in Gas Chromatography

A series of silica-supported polymeric ionic liquid (PIL)-based stationary phases derived from a vinylic L-valine ionic liquid monomer and divinylbenzene (DVB) as the crosslinking agent have been prepared and studied as gas chromatographic stationary phases. These coated gas chromatographic columns exhibited good thermal stabilities (230-300 °C) and high efficiencies (1700-2700 plates/m), and were characterized using a linear solvation parameter model in order to understand the effects of the amount of DVB on the features of the resulting composite systems. Their retention behavior and separation efficiencies were demonstrated using the Grob test. By tuning the crosslinking degree for the IL-derived stationary phase, the separation selectivity and resolution of different compounds were improved. The different retention behaviors observed for many analytes indicate that these stationary phases may be applicable as new types of GC stationary phases.

Nanoconfined Crosslinked Poly(ionic liquid)s with Unprecedented Selective Swelling Properties Obtained by Alkylation in Nanophase-Separated Poly(1-vinylimidazole)-l-poly(tetrahydrofuran) Conetworks

Despite the great interest in nanoconfined materials nowadays, nanocompartmentalized poly(ionic liquid)s (PILs) have been rarely investigated so far. Herein, we report on the successful alkylation of poly(1-vinylimidazole) with methyl iodide in bicontinuous nanophasic poly(1-vinylimidazole)-l-poly(tetrahydrofuran) (PVIm-l-PTHF) amphiphilic conetworks (APCNs) to obtain nanoconfined methylated PVImMe-l-PTHF poly(ionic liquid) conetworks (PIL-CNs). A high extent of alkylation (~95%) was achieved via a simple alkylation process with MeI at room temperature. This does not destroy the bicontinuous nanophasic morphology as proved by SAXS and AFM, and PIL-CNs with 15-20 nm d-spacing and poly(3-methyl-1-vinylimidazolium iodide) PIL nanophases with average domain sizes of 8.2-8.4 nm are formed. Unexpectedly, while the swelling capacity of the PIL-CN dramatically increases in aprotic polar solvents, such as DMF, NMP, and DMSO, reaching higher than 1000% superabsorbent swelling degrees, the equilibrium swelling degrees decrease in even highly polar protic (hydrophilic) solvents, like water and methanol. An unprecedented Gaussian-type relationship was found between the ratios of the swelling degrees versus the polarity index, indicating increased swelling for the nanoconfined PVImMe-l-PTHF PIL-CNs in solvents with a polarity index between ~6 and 9.5. In addition to the nanoconfined structural features, the unique selective superabsorbent swelling behavior of the PIL-CNs can also be utilized in various application fields.

The Electric Field Responses of Inorganic Ionogels and Poly(ionic liquid)s

Ionic liquids (ILs) are a class of pure ions with melting points lower than 100 °C. They are getting more and more attention because of their high thermal stability, high ionic conductivity and dielectric properties. The unique dielectric properties aroused by the ion motion of ILs makes ILs-contained inorganics or organics responsive to electric field and have great application potential in smart electrorheological (ER) fluids which can be used as the electro-mechanical interface in engineering devices. In this review, we summarized the recent work of various kinds of ILs-contained inorganic ionogels and poly(ionic liquid)s (PILs) as ER materials including their synthesis methods, ER responses and dielectric analysis. The aim of this work is to highlight the advantage of ILs in the synthesis of dielectric materials and their effects in improving ER responses of the materials in a wide temperature range. It is expected to provide valuable suggestions for the development of ILs-contained inorganics and PILs as electric field responsive materials.

Synthesis and Characterization of Ionic Graft Copolymers: Introduction and In Vitro Release of Antibacterial Drug by Anion Exchange

Amphiphilic graft copolymers based on [2-(methacryloyloxy)ethyl]trimethyl- ammonium chloride (TMAMA) were obtained for the delivery of pharmaceutical ionic drugs, such as p-aminosalicylate (PAS) and clavunate (CLV) anions. The side chains were attached by grafting from a multifunctional macroinitiator via atom transfer radical polymerization (ATRP) to get polymers with different grafting degrees and ionic content. The self-assembling ability, confirmed by determining the critical micelle concentration (CMC) through interfacial tension (IFT) with the use of goniometry, was reduced after ion exchange (CMC twice higher than for chloride anions contained copolymers 0.005-0.026 mg/mL). Similarly, the hydrophilicity level (adjusted by the content of ionic fraction) evaluated by the water contact angle (WCA) of the polymer film surfaces was decreased with the increase of trimethylammonium units (68°-44°) and after introduction of pharmaceutical anions. The exchange of Cl- onto PAS- and CLV- in the polymer matrix was yielded at 31%-64% and 79%-100%, respectively. The exchange onto phosphate anions to release the drug was carried out (PAS: 20%-42%, 3.1-8.8 μg/mL; CLV: 25%-73%, 11-31 μg/mL from 1 mg of drug conjugates). Because of the bacteriostatic activity of PAS and the support of the action of the antibiotics by CLV, the designed water-soluble systems could be alternatives for the treatment of bacterial infections, including pneumonia and tuberculosis.

Ionic Polyureas-A Novel Subclass of Poly(Ionic Liquid)s for CO2 Capture

The growing concern for climate change and global warming has given rise to investigations in various research fields, including one particular area dedicated to the creation of solid sorbents for efficient CO2 capture. In this work, a new family of poly(ionic liquid)s (PILs) comprising cationic polyureas (PURs) with tetrafluoroborate (BF4) anions has been synthesized. Condensation of various diisocyanates with novel ionic diamines and subsequent ion metathesis reaction resulted in high molar mass ionic PURs (Mw = 12 ÷ 173 × 103 g/mol) with high thermal stability (up to 260 °C), glass transition temperatures in the range of 153-286 °C and remarkable CO2 capture (10.5-24.8 mg/g at 0 °C and 1 bar). The CO2 sorption was found to be dependent on the nature of the cation and structure of the diisocyanate. The highest sorption was demonstrated by tetrafluoroborate PUR based on 4,4'-methylene-bis(cyclohexyl isocyanate) diisocyanate and aromatic diamine bearing quinuclidinium cation (24.8 mg/g at 0 °C and 1 bar). It is hoped that the present study will inspire novel design strategies for improving the sorption properties of PILs and the creation of novel effective CO2 sorbents.

Structural Regulation of Magnetic Polymer Microsphere@Ionic Liquids with an Intermediate Protective Layer and Application as Core-Shell-Shell Catalysts with High Stability and Activity

A novel ionic liquid immobilized on a magnetic polymer microsphere catalyst is reported in this paper. The obtained core-shell-shell catalyst consisted of magnetic nanoparticles (MNPs) as the core, catalytic inert St-co-DVB as the intermediate protective layer, and cross-linked polyaryl imidazole ionic liquids as the active catalytic layer located at the outermost [Im[OH]/MNPs@P(St-DVB)@P(VBC-DVB)]. This catalyst exhibited a high ion-exchange rate (64.65%), high saturation magnetic strength, and excellent acid and alkali corrosion resistance. In the catalyzed Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate, the conversion of benzaldehyde maintained at 92.1% during six times reuse. Optimizing the materials of the protective layer and regulating the thickness of the inert protective layer decreased the corrosion ratio of MNPs in acidic media from 44.82 to 0.44%. Adjusting the thickness of the catalytic layer realized excellent catalytic activity (97%) and high magnetic response performance. In summary, introducing an inert protective layer to the structure of ionic liquids immobilized on the magnetic polymer microsphere catalyst, regulating its thickness, and optimizing its structure achieved a catalyst with high activity, excellent stability, and easy magnetic separation.

Ion transport in small-molecule and polymer electrolytes

Solid-state polymer electrolytes and high-concentration liquid electrolytes, such as water-in-salt electrolytes and ionic liquids, are emerging materials to replace the flammable organic electrolytes widely used in industrial lithium-ion batteries. Extensive efforts have been made to understand the ion transport mechanisms and optimize the ion transport properties. This perspective reviews the current understanding of the ion transport and polymer dynamics in liquid and polymer electrolytes, comparing the similarities and differences in the two types of electrolytes. Combining recent experimental and theoretical findings, we attempt to connect and explain ion transport mechanisms in different types of small-molecule and polymer electrolytes from a theoretical perspective, linking the macroscopic transport coefficients to the microscopic, molecular properties such as the solvation environment of the ions, salt concentration, solvent/polymer molecular weight, ion pairing, and correlated ion motion. We emphasize universal features in the ion transport and polymer dynamics by highlighting the relevant time and length scales. Several outstanding questions and anticipated developments for electrolyte design are discussed, including the negative transference number, control of ion transport through precision synthesis, and development of predictive multiscale modeling approaches.

Thin Porous Poly(ionic liquid) Coatings for Enhanced Headspace Solid Phase Microextraction

In this contribution, thin poly(ionic liquid) (PIL) coatings with a well-defined pore structure built up from interpolyelectrolyte complexation between a PIL and poly(acrylic acid) (PAA) were successfully used for enhanced solid phase microextraction (SPME). The introduction of porosity with tunable polarity through the highly versatile PIL chemistry clearly boosts the potential of SPME in the detection of compounds at rather low concentrations. This work will inspire researchers to further explore the potential of porous poly(ionic liquid) materials in sensing and separation applications.

Impact of Imidazolium-Based Ionic Liquids on the Curing Kinetics and Physicochemical Properties of Nascent Epoxy Resins

We investigated the influence of anion type (salicylate, [(MOB)MIm][Sal], vs chloride, [(MOB)MIm][Cl]) of imidazolium-based ionic liquid (IL) and its content on the curing kinetics of bisphenol A diglicydyl ether (DGEBA of molecular weight M n = 340 g/mol). Further physicochemical properties (i.e., glass transition temperature, T g, and conductivity, σdc) of produced polymers were investigated. The polymerization of the studied systems was examined at various molar ratios (1:1, 10:1, and 20:1) at different reaction temperatures (T reaction = 353-383 K) by using differential scanning calorimetry (DSC). Interestingly, both DGEBA/IL compositions studied herein revealed significantly different reaction kinetics and yielded materials of completely distinct physical properties. Surprisingly, in contrast to [(MOB)MIm][Cl], for the low concentration of [(MOB)MIm][Sal] in the reaction mixture, an additional step in the kinetic curves, likely due to the combined enhanced initiation activity of anion (salicylate)-cation (imidazolium-based), was noted. To thoroughly analyze the kinetics of all studied systems, including the two-step kinetics of DGEBA/[(MOB)MIm][Sal], we applied a new approach that relies on the combination of the two phenomenological Avrami equations. Analysis of the determined constant rates revealed that the reaction occurring in the presence of the salicylate anion is characterized by higher activation energy with respect to those with the chloride. Moreover, DGEBA/[(MOB)MIm][Sal] cured materials have higher T g in comparison to DGEBA polymerized with [(MOB)MIm][Cl] independent of the IL concentration. This fact might indicate that, most likely, the products of hardening are highly cross-linked (high T g) or oligomeric linear polymers (low T g) in the former and latter cases, respectively. Such a change in the chemical structure of the polymer is also reflected in the dc conductivity measured at the glass transition temperature, which is much higher for DGEBA cured with [(MOB)MIm][Cl]. Herein, we have clearly demonstrated that the type of anion has a crucial impact on the polymerization mechanism, kinetics, and properties of produced materials.

Stimuli-responsive poly(ionic liquid) nanoparticles for controlled drug delivery

A poly(ionic liquid) (PIL) obtained by polymerizing an ionic liquid (IL) monomer exhibits the characteristics of low cost and good biocompatibility, and it retains the excellent properties of the monomer. However, there is still a need to develop PILs for biomedical applications, which has been paid little attention. Herein, an amphiphilic block polymer containing a PIL block is synthesized, which simultaneously includes a targeted ligand, a photo-responsive block, and a pH-responsive block. The resultant amphiphilic block polymer can self-assemble into drug-loaded nanoparticles with a size of ∼80 nm in aqueous solution, and its drug loading capacity is as high as 70%. Moreover, the drug releasing mechanism of these drug-loaded nanoparticles can be triggered by light and pH stimuli. These novel amphiphilic PIL-based drug-loaded nanoparticles show highly effective antitumor effects, providing a promising approach for the delivery and controlled release of chemotherapy drugs in cancer therapy.

Preparation and Morphology Control of Poly(ionic liquid) Particles

Poly(ionic liquid)s (PILs) are prepared by the polymerization of ionic liquid (IL) monomers that have polymerizable groups on their cationic or anionic component. PILs also share many of the characteristic properties of ILs and can be used in various materials such as CO₂ sorbents, polymer electrolytes, dispersants, and microwave-absorbing materials. In this feature article, we survey our research, focusing on the preparation of PILs in the particulate state (PIL particles) and on the morphological control of the PIL particles, including (1) the preparation of PIL particles by dispersion polymerization and emulsion polymerization, (2) control of the morphology of composite particles consisting of a PIL and poly(methyl methacrylate) (PMMA), (3) the preparation of hollow particles with a PIL shell, and (4) the preparation of PIL particles containing reduced graphene oxide (rGO). The size of the obtained PIL particles could be controlled through a modification of the synthesis conditions and the mode of polymerization (i.e., dispersion polymerization or emulsion polymerization). The obtained PIL particles maintained the characteristic properties of the corresponding ILs; moreover, the solubility of the PIL particles could be easily modified by changing their counteranion. Using seeded polymerization, we prepared PMMA/PIL composite polymer particles and subsequently demonstrated that their morphology can be manipulated to yield a core-shell or Janus structure. Hollow particles consisting of a PIL shell were also prepared, and modification of the polarity and penetration behavior of the shell through anion exchange was demonstrated.