Type Of Counterion Research Articles

Enhanced interfacial polarization and electro-responsive characteristic of di-ionic poly(ionic liquid)s

Poly(ionic liquid)s are providing potential platforms to develop new generation of water-free polyelectrolyte-based electorheological materials due to strong polarizability and intrinsic hydrophobicity. To enhance polarization and electro-response by employing combined contribution of ion number density and ion transport dynamic, we here have developed a kind of di-ionic poly(ionic liquid)s for use as new electorheological materials. It has found that di-ionic poly(ionic liquid)s have enhanced electorheological effect compared with common mono-ionic poly(ionic liquid)s but enhancement degree depends on counterion type. The enhancement of di-ionic poly(ionic liquid)s with PF6− as counterions is more significant than those with TFSI− as counterions. By combining dielectric spectra with Raman and X-ray scattering analyses, it has demonstrated that enhanced electorheological effect of di-ionic poly(ionic liquid)s is because di-ionic structure can increase interfacial polarization by combined contribution of enhanced ion number density and transport dynamic. However, the enhancement degree is more significant for PF6− than TFSI− due to its small size and low plasticizing capacity.

Aggregation−induced emissions in columnar wedge−shaped pyridinium−based ionic liquid crystals

Two series of ILCs derived from wedge−shaped N-phenylpyridiniums 1–2 were prepared and their mesomorphic properties were investigated. The X−ray crystal structure analyses of two single crystals 2-PF6 (n = 12) and 2-NTf2 (n = 12) revealed that bilayer structures induced by H−bonds in the solid state were observed. A complementary dimeric structure induced by H−bonds in such type of wedge−shaped cation (or anion) moiety was attributed to the formation of columnar phases. The type of counter anions has a significant influence on the formation of the mesophase; five counter anions (i.e. X = PF6‾, BF4‾, OTf‾, SCN‾, RSO3‾) induced columnar mesophase. In contrast, anion X = Tf2N‾ as a bulky moiety and less H−bond active sites formed crystal phase. The powder XRD data appeared that the diameter of the hard columnar part increased with the effective ionic radius for different counter ion. A linear correlation plot (R2 = 0.9203) was obtained. All ethanol solutions of compounds 1–2 were detected without any observable signals on photoluminescence. But compounds 2-X will aggregate in the aqueous mixture with high water fractions (ƒw) needed to turn on their light emission process. Weak PL signals are recorded at ƒw < 50% because the luminogens 2-OTf are fully dissolved and quenched in these solvent compositions. The PL intensity started to enhance at ƒw > 50% till it reached to the maximum intensity at ƒw ~70%.

Enhancement of exfoliating efficacy of L-carnitine with ion-pair method monitored by nuclear magnetic resonance spectroscopy

Carnitine (CAR), an amino acid derivative, has great potential as a facial exfoliating agent owing to its calcium chelating property under weakly acidic or neutral conditions. However, its application is limited by its poor transdermal penetration. To optimise its exfoliation efficacy with minimal concentration, we propose the ion-pair method. The ionic interaction between CAR and a zwitterionic substance was successfully monitored by measuring conductivity. The alterations of penetration and exfoliation efficacy for CAR addition to different types of counter ions were investigated in vitro and in vivo. We found that hydrogenated soya phosphatidylcholine (HSC), an amphiphilic counter ion, significantly increases the stratum corneum penetration and exfoliation efficacy of CAR. The changes of the CAR-HSC ionic interaction in the presence of calcium ions were also investigated by 1H nuclear magnetic resonance (NMR) spectroscopy. The NMR spectra for amino groups of CAR first decreased with HSC and then gradually recovered and shifted as calcium ions were added. From the results, a noble exfoliating complex of CAR with high exfoliation efficacy could be proposed. Moreover, the results demonstrate that NMR spectroscopy is useful to obtain direct experimental evidence of the molecular dynamics simulations of the alteration of an exfoliating complex as it penetrates.

Modeling the influence of divalent ions on membrane resistance and electric power in reverse electrodialysis

The prospects and potential of Reverse Electrodialysis (RED) for energy harvesting from natural streams with salinity gradient demand more in-depth studies to understand and overcome the limitations posed by divalent ions. Power performance is greatly influenced by the ionic resistance displayed by the alternating cation and anion exchange membranes (CEMs and AEMs, respectively) housed in RED stacks, which in turn is determined by the type and concentration of ions and counter-ions in the water streams. The effects of divalent ions on power output have been experimentally approached in several works by using real or synthetic water. However, the development of comprehensive models including the effect of divalent ions on membrane resistance and power performance under different scenarios is still very scarce. Thus, this work investigates experimentally the effect of ion species on membrane resistance, providing for the first time mathematical correlations useful to predict power performance in RED stacks under a wide range of compositions of salinity gradient solutions. To this end, electrochemical impedance spectroscopy (EIS) measurements have been performed for CEM and AEM commercial membranes in contact with different concentration of NaCl solutions and including different mixtures of divalent ions (Ca2+, Mg2+, SO42−). These correlations have been implemented in a previously developed model to determine power outputs as function of ion mixture compositions. Scenarios of general interest for RED practical implementation have been addressed; specifically, solutions with a composition representative of seawater or high salinity brines have been studied as high concentration solutions (HCS) and, on the other hand, typical concentrations of wastewater treatment plant effluents, river water or brackish water from desalination plants were used as low concentration solutions (LCS).

Role of Counterions and Nature of Spacer on Foaming Properties of Novel Polyoxyethylene Cationic Gemini Surfactants

Application of foam in various upstream operations, such as in enhanced oil recovery, has gained significant attention in recent years. A good foaming agent should generate a stable foam, must be thermally stable (&gt;90 °C, typical reservoir temperature), must have a high tolerance to salinity, and should have low adsorption on the reservoir rock. In view of this, four thermally stable and salt-tolerant polyoxyethylene cationic gemini surfactants were synthesized with different spacers (mono phenyl and biphenyl) and different counterions (Br− and Cl−). Foaming properties were evaluated using initial foam generation, foam volume stability at a given time, bubble count, and average foam bubble radius. The effect of counterions and nature of spacers, with and without the presence of salts, on foaming properties was evaluated. It was found that number of phenyl rings (mono phenyl and biphenyl) had no significant effect on foamability and foam stability in the presence or absence of salts. However, the effect of counterions was prominent in deionized water. In deionized water, foam generated by gemini surfactants with bromide as a counterion was more stable compared to the foam generated using the surfactant containing chloride as the counterion. In saline solution, the type of counterion had no effect on the foamability or foam stability of the foam generated using synthesized cationic gemini surfactants. The foam volume stability decreased by the addition of salts; however, a further increase in salt concentration enhanced the foam volume stability. The synthesized surfactants showed good thermal stability, salt tolerance, and foaming properties and can be an attractive choice for upstream applications.

Surface modified natural zeolites (SMNZs) as nanocomposite versatile materials for health and environment

The present research deals with the evaluation of a clinoptilolite-rich rock, occurring in the Nižný Hrabovec deposit (Slovakia), for high-value technological applications based on sorption and in vitro release of nonsteroidal anti-inflammatory drugs (i.e., ibuprofen sodium salt). This georesource was surface modified (SMNZ) using four cationic surfactants. Results demonstrate that ibuprofen sorption is very fast and SMZNs can sorb up to ˜26 mg/g of drug as a function of the type of counterion and morphology of surfactant, as well as the hydrophobicity and molecular structure of the drug. Maximum sorption capacities observed for all SMNZs are fully comparable to other adsorbent carriers usually used for removal of contaminants in wastewaters. Sorption of ibuprofen is controlled by a dual mechanism: external anionic exchange and partition into the hydrophobic portion of the patchy bilayer. A prompt drug release in simulated intestinal fluid (SIF) was also observed, making this natural material also suitable to provide rapid soothing effects in potential pharmacological applications.Comparing the results of this study with other recent investigations, a good technological performance of clinoptilolite-rich rock can be inferred despite the relatively low zeolite content (˜56 wt.%).

Coordination polymers of CdII and PbII derived from bipyridine-glycoluril: influence of metal-ion size and counter-ions.

Two new one-dimensional (1D) coordination polymers (CPs), namely catena-poly[[[aquacadmium(II)]-bis(μ-4b,5,7,7a-tetrahydro-4b,7a-epiminomethanoimino-6H-imidazo[4,5-f][1,10]phenanthroline-6,13-dione)] bis(perchlorate) dihydrate], {[Cd(C14H10N6O2)2(H2O)](ClO4)2·2H2O}n or {[Cd(BPG)2(H2O)](ClO4)2·2H2O}n, 1, and catena-poly[[lead(II)-bis(μ-4b,5,7,7a-tetrahydro-4b,7a-epiminomethanoimino-6H-imidazo[4,5-f][1,10]phenanthroline-6,13-dione)] bis(perchlorate) dihydrate], {[Pb(C14H10N6O2)2](ClO4)2·2H2O}n or {[Pb(BPG)2](ClO4)2·2H2O}n, 2, have been synthesized using bipyridine-glycoluril (BPG; systematic name: 4b,5,7,7a-tetrahydro-4b,7a-epiminomethanoimino-6H-imidazo[4,5-f][1,10]phenanthroline-6,13-dione), a urea-fused tecton, in a mixed-solvent system. The CdII ion in 1 is heptacoordinated and the PbII ion in 2 is hexacoordinated, with the CdII ion adopting a pentagonal bipyramidal geometry and the PbII ion adopting a distorted octahedral geometry. Both CPs form infinite linear chain structures which are hydrogen bonded to each other leading to the formation of three-dimensional supramolecular network structures. Topological analysis of CPs 1 and 2 reveals that the structures exhibit 1D chain-like arrangements in an AB-AB sequence and shows platonic uniform 2-connected uninodal topologies. Furthermore, a comparative analysis of a series of structures based on the BPG ligand indicates that the size of the metal ion and the types of counter-ions used have a great influence on the resulting frameworks and properties.

Removal of phosphate by Donnan dialysis coupled with adsorption onto calcium alginate beads.

In this study the removal of phosphates from solution by Donnan dialysis and by adsorption onto calcium alginate beads were studied separately and then together. This hybrid process was conducted in order to benefit from each process, and it is an original and new combination. First, the Donnan dialysis process was performed with different parameters: the type of counter-ion, the concentration of the counter-ion, the initial phosphate concentration, the pH of the solution and the choice of anion-exchange membranes. Donnan dialysis achieved 68% and 12.5% phosphorus removal with AMX and AFN membranes respectively. Then a preliminary study into the adsorption of phosphate onto calcium alginate beads was carried out. A full factor design was applied in order to determine the effect of the main parameters and their mutual interactions for the adsorption process. The removal of phosphate onto calcium alginate beads reached 82.5%. Finally, coupling Donnan dialysis with adsorption onto calcium alginate beads for the removal of phosphate reached 89.5% with the AMX membrane. This hybrid process can be considered to be a solution for improving the contact time and for enhancing the removal of phosphate by 10% compared to adsorption onto calcium alginate.

Ion transport, polarization and electro-responsive elelctrorheological effect of self-crosslinked poly(ionic liquid)s with different counterions

Self-crosslinked bis(imidazolium)-based poly(ionic liquid)s (PILs) containing different counterions (P[C2DVIM][X], X = BF4−, PF6−, TfO−, TFSI−) are synthesized and the influence of counterions on electro-responsive electrorheological (ER) effect is studied in order to understand the structure-property relationship of crosslinked PIL-based ER system. It is found that the size and type of counterions have a significant influence on ER effect. As the size increases, the ER effect decreases (i.e. BF4− > PF6− > TfO− > TFSI−). Different from the linear PIL-based ER system, however, the P[C2DVIM]X with inorganic counterions shows stronger ER effect compared to P[C2DVIM]X with organic counterions. Meanwhile, the influence of counterions on temperature dependence of ER effect of the crosslinked PIL system is also different from the linear PIL system. By dielectric spectroscopy and X-ray scattering measurements, the mechanism behind the influence is analyzed. It demonstrates that, different from linear PIL system, the ionic aggregation is largely weakened in P[C2DVIM]X and the transport of mobile counterions and interfacial polarization are mainly dominated by the mesh size of crosslinking network. This should be responsible for the different dependence of ER effect on the size and type of counterions between self-crosslinked and linear PIL systems.

Sulfonated poly(ether ether ketone) membrane for quinone-based organic flow batteries

Over the past few years, organic flow batteries have gained immense attention owing to their potential for large-scale energy storage applications and modifiable properties. Organic redox couples usually involve only one type of counter-ion for ion exchange membranes, and hence provide opportunities to use low-cost membranes in organic flow batteries. In this study, we prepared a sulfonated poly (ether ether ketone) (sPEEK) membrane for application in acidic flow batteries of 1,2-dihydroxybenzene-3,5-disulfonic acid/anthraquinone-2-sulfonic acid. The proton conductivity of the prepared sPEEK membrane was 50% lower than that of Nafion-212 membrane. However, the Coulombic efficiency of the sPEEK cell was similar to that of Nafion cell, and the voltage efficiency was 0.99%–2.66% higher than that of Nafion cell at different current densities. The cell using the sPEEK membrane also exhibited long-term stability, retaining 96.93% reversible capacity after 100 charge/discharge cycles at the current density of 100 mA cm−2. The results of symmetric cell cycling indicated that the decay of reversible capacity in this organic flow battery system was mainly due to the instability of organic compounds in the positive electrolyte, which was also confirmed by the self-discharge measurements of the sPEEK cell. These results demonstrate that the sPEEK membrane is highly suitable for organic flow batteries. These results will be helpful for realizing cost-effective energy storage systems.

A comparative study of the counterion effect on the perrhenate-catalyzed deoxydehydration reaction

Counterions have a significant effect on the efficiency of the deoxydehydration (DODH) reaction. Four perrhenate salts, Z+ReO4− (Z = Na+, K+, NH4+, and Bu4N+), were tested in the DODH reaction of a vicinal diol in the presence of PPh3 as the reductant. In addition, a new perrhenate salt, (2-ppyH)[ReO4] (2-ppyH+ = 2-phenylpyridinium cation), has been synthesized and characterized by X-ray crystallography and utilized as an efficient catalyst in the DODH reaction. Since so far computational studies related to the influence of the counterion in the different steps of the DODH mechanism are scarce, we have carried out a comparative investigation of the counterion effect using density functional theory (DFT) calculations. The DODH mechanism of the conversion of phenyl-1,2-ethanediol to styrene in the presence of the five perrhenate salts mentioned above, as well as bare perrhenate (ReO4−) was studied from an energetic point of view. The catalytic tests and concomitant DFT computations confirmed the general mechanistic aspect in which the counterion plays an active role in all stages of the reaction mechanism including intermediate structures, Gibbs free energy changes (ΔG°g and ΔG°sol), transition states, and activation barrier energies. The role of counterion type has been considered in three key steps of the reaction mechanism, including the proton-transfer from diol to oxo-ligand in the rhenium moiety, the nucleophilic attack of the P atom from PPh3 on the oxo-ligand, the dissociation of the OPPh3 ligand, and the olefin extrusion from the Re(V)-diolate intermediate for each perrhenate salt. The crucial roles played by the counterion in terms of structure arrangement during transition states and the activation energy barriers are finally discussed.

Demulsification of water-in-oil emulsions using ionic liquids: Effects of counterion and water type

Demulsification of crude oil emulsions is of significant interest in the petroleum industry. This study aims to investigate the effect of ionic liquid (IL) counterions and water type (distilled water (DW) and laboratory formulated seawater (SW)) on the demulsification of water-in-oil (W/O) emulsions. Three ILs belonging to the phosphonium compounds with different counterions were used. These ILs were designated as THPC (contains chloride ion), THPD (contains decanoate ion), and THPDc (contains dicyanamide ion). Emulsions were formed using DW and SW while demulsification tests were conducted at temperatures of 60 °C and 80 °C. According to the demulsification outcomes at 60 °C, THPC was the best candidate for breaking W/O emulsions produced from DW while THPD and THPDc were excellent candidates for destabilizing emulsions produced from SW. The optimal percentage demulsification efficiency (DE) achieved for emulsions from DW was 99% with just 1000 ppm THPC while 1000 ppm THPD and 700 ppm THPDc are adequate to bring about excellent water separation in emulsions formulated from SW. THPD and THPDc also attained the maximum percentage DE of 99%.On the other hand, at elevated temperature (80 °C), THPC, THPD, and THPDc attained nearly the same water separation in the W/O emulsions produced from DW and SW with a demulsifying capacity of 99%. However, demulsification activities at this temperature (80 °C) in the W/O emulsions formed using SW were very fast as compared to what was observed in the case of emulsions obtained from DW. Thus, salts present in SW have propensities to accelerate the destabilization of crude oil emulsions. Viscosity and elastic modulus time sweep measurements reveal that the tested ILs can collapse the natural emulsifiers (asphaltenes and resins) existing at the water-oil interfaces.

Copper(ii) self-assembled clusters of bis((pyridin-2-yl)-1,2,4-triazol-3-yl)alkanes. Unusual rearrangement of ligands under reaction conditions.

The reaction of two structurally related bridging ligands bis[5-(2-pyridyl)-1,2,4-triazole-3-yl]methane (H2L1) and bis[5-(2-pyridyl)-1,2,4-triazole-3-yl]ethane (H2L2) with copper(ii) salts resulted in a surprising wide variety of complex structures [Cu2(H2L1)Cl2]Cl2·4CH3OH (1), [Cu4(L1)4]·4H2O (2), [Cu(H2L2)(ClO4)2] (3) and [Cu3(OH)Na2(L')6](ClO4)·5H2O·C3H6O (4), where HL' is 3,5-bis-(pyridin-2-yl)-1,2,4-triazole, which were structurally characterized by the X-ray diffraction method. Complexes 1 and 2 were prepared on the H2L1 basis and have binuclear and tetranuclear structures, respectively, demonstrating strong impact of the type of counter anion on the coordination mode of the ligand. In contrast, the reaction between Cu(ClO4)2 6H2O and H2L2 led to the preparation of mononuclear complex 3. The reaction of H2L2 with Cu(ClO4)2 under alkaline conditions led to oxidative rearrangement of the ligand and the homoleptic pentanuclear complex 4 with anionic ligand L' was prepared. Magnetic properties were studied for compounds 1, 2 and 4 and for all of them the antiferromagnetic interactions between the Cu atoms were confirmed and analyzed by the spin Hamiltonian formalism. Furthermore, the occurrence of the antisymmetric exchange was confirmed in 4. The magnetic data analysis was supported by the X-band EPR measurements performed for complexes 1, 2 and 4.

Influence of divalent counterions on the solution rheology and supramolecular aggregation of carboxymethyl cellulose

Divalent counterions promote attractive forces between polyelectrolyte chains via electrostatic bridging, which play an important role in the conformation of ionic biopolymers. Further, counterion valence is known to affect the flexibility and aggregation properties of polyelectrolytes in solution. The present study seeks to resolve the effect of counterion valence and type on the structure and flow properties of a model semiflexible polyelectrolyte. We report rheology and light scattering data for the Na $$^+$$ , Mg $$^{2+}$$ , Ca $$^{2+}$$ , Mn $$^{2+}$$ , Co $$^{2+}$$ , Ba $$^{2+}$$ salts of carboxymethyl cellulose in aqueous solutions. The Na $$^+$$ and Mg $$^{2+}$$ counterions do not interact specifically with the carboxylate groups, and their CMC salts form clear solutions in the concentration (c) range studied (0.001 M 0.2 M. Compared NaCMC, divalent salts display a lower viscosities at low concentrations (in the non-entangled regime), suggesting less expanded chains, in agreement with earlier experimental results on flexible polyelectrolytes. Above the entanglement crossover ( $$c \simeq$$ 0.07 M), solutions with divalent counterions display viscosities up to an order of magnitude larger than NaCMC, possibly because interchain crosslinks form by electrostatic bridging. Dynamic light scattering measurements on semidilute non-entangled solutions reveal a bimodal decay function, where the relative amplitudes of the two modes vary with counterion valence, size as well as with the filter size employed and the time after filtration. These variables (except for counterion valency) do not strongly affect the solution viscosity, indicating that polyelectrolyte clusters only contain a small fraction of the total number of chains in solution.

Kinetics, Thermodynamics, and Competitive Adsorption of Heavy Metals from Water Using Orange Biomass.

Adsorption of heavy metals on modified orange biomass has been studied. This biomass was treated with NaOH and CaCl₂ to improve its adsorption properties. Kinetic and thermodynamic studies of the adsorption of Cd2+, Ni2+, Cu2+, and Zn2+ were performed at different operating conditions, including competitive adsorption studies with binary metallic mixtures. Results show that this adsorption process was endothermic where an ion exchange mechanism played a relevant role. Adsorbent effectiveness decreased in binary solutions, indicating a strong antagonistic adsorption behavior caused by counter-ions. This antagonistic adsorption was highly dependent on the counter-ion type and its concentration. Multicomponent adsorption of Cu2+ ions was not significantly affected by the presence of other metallic counter-ions, whereas the adsorption of Ni2+ could be totally suppressed by the other ions. The modeling of binary adsorption isotherms was successful using the modified Langmuir equation, which outperformed the Ideal Absorbed Solution Theory-Sips and modified Redlich-Peterson models.

Why Does RNA Collapse? The Importance of Water in a Simulation Study of Helix-Junction-Helix Systems.

Using computer simulations, we consider the balance of thermodynamic forces that collapse RNA. A model helix-junction-helix (HJH) construct is used to investigate the transition from an extended to a collapsed conformation. Conventional Molecular Dynamics and Milestoning Simulations are used to study the free energy profile of the process for two ion concentrations. We illustrate that HJH folds to a collapsed state with two types of counterions (Mg2+ and K+). By dissecting the free energy landscape into energetic and entropic contributions, we illustrate that the electrostatic forces between the RNA and the mobile ions do not drive the RNA to a collapsed state. Instead, entropy gains from water expulsion near the neighborhood of the RNA provide the stabilization free energy that tilt HJH into more compact structures. Further simulations of a three-helix hammerhead ribozyme show a similar behavior and support the idea of collapse due to increased gain in water entropy.

Poly(phenylene) synthesized using diels-alder chemistry and its sulfonation: Sulfonate group complexation with metal counter-ions, physical properties, and gas transport

Sulfonated poly(phenylene) (sPP) thermal stability, physical properties, and gas transport characteristics were evaluated as a function of ion-exchange capacity (x = IEC), and counter-ion type (M = H+, Cs+, Na+, Mg2+, and Al3+). Counter-ion substitution with its sulfonated groups produced Δv(SO3-) vibrational shifts that were related to ion type and valence observed using FTIR. Increasing IEC and counter ion complexation strength within sPP led to greater density and reduced fractional free volume (FFV). sPPx-M exhibited a single thermal degradation step greater than 550 °C that decreased with increasing IEC. Unsulfonated poly(phenylene) (PP) had a glass transition at 391 °C, which shifted to 420 °C upon sulfonation. Thermal stability and mechanical properties increased with counter-ion type in the following order: sPP2.5-Cs+ < sPP2.5-Na+ < sPP2.5-Mg2+. However, decreased thermal stability and physical properties were observed using Al3+ as a counter-ion (sPP2.5-Al3+). He, H2, CO2, N2, O2 and CH4 permeability decreased within sPP2.5-M based upon counter-ion type, size, and valence. Larger CO2 and H2 molecules were more permeable than He, which revealed a more complex transport process was occurring within sPP2.5. Metal-ion complexation with sPP2.5 significantly reduced CO2 and H2 permeability. PP possessed high CO2 permeability (152 Barrers) with moderate CO2/CH4 selectivity (12.6). sPP2.5-Na+ (IEC = 2.5 meq/g) had a CO2/CH4 selectivity of 71.3, and counter-ion substitution to create sPP2.5-Cs+ increased CO2/CH4 selectivity by 23%. Gas solubility and diffusivity decreased with increasing IEC and metal-ion complexation strength. sPPx-M had tunable ideal gas permselectivity that was largely a function of sulfonate group concentration and counter-ion type.

Micellar Effects on the Hydrolysis Reaction of an Anionic Surfactant in Aqueous Solution

The hydrolysis mechanisms of 2-sulfoalkanoic acid methyl ester salts (methyl ester sulfonate, MES) were studied. Under acidic, neutral, and alkaline conditions, the hydrolysis rates of MES were strongly affected by the state of aggregation and the hydrolysis rate changed at the critical micelle concentration (CMC). Under acidic conditions, the hydrolysis rates of MES were enhanced by micellar formation and correlated quantitatively with the amount of protons bound on the micellar surfaces being measured by the electric conductivity along with fluorescence and hydrogen-ion electrode measurements. MES having longer acyl chain lengths showed higher hydrolysis rates above the CMC because of the many bound protons and the higher degree of counterion binding to the micelle, β. The rates were affected by the type of counterion and followed the order of sodium > potassium > calcium salts of MES. In alkaline conditions, the rates of MES hydrolysis were suppressed to lower values by micelle formation and MES with longer acyl chain lengths showed lower rates above the CMC. Additionally, the hydrolysis rates of MES under neutral conditions were suppressed to a very low value by micelle formation. These mechanisms of inhibitory effect of hydrolysis by the aggregation should be dominated by the electrical repulsive interactions between hydroxyl anions and anionic micellar surfaces, as well as by interference with the penetration of the hydroxyl anion to the ester group in the micelles for alkaline hydrolysis and by interference from water molecules for neutral hydrolysis.

How does the type of counterion influence the polymerization rate and thermal properties of tailored choline‐based linear‐ and star‐shaped poly(ionic liquid)s PILs?

ABSTRACTThe synthesis of tailored [2‐(methacryloyloxy)ethyl]‐trimethylammonium chloride (ChMA/Cl−) and bis(trifluoromethanesulfonate) imide (ChMA/NTf2−)‐based ionic homopolymers by sustainable activators generated by electron transfer atom transfer radical polymerization (ATRP) method has been demonstrated. Linear and four‐arm star‐shaped macromolecules were obtained with the use of two synthetic strategies: (a) direct polymerization of ionic monomers with counterions differing in hydrophilicity (prepolymerization) and (2) modification by ion exchange from Cl− to NTf2− (postpolymerization) using both classical ATRP initiator and pentaerythritol‐based initiator. The effect of counterions on the polymerization kinetics and the physicochemical and thermodynamical properties of resulted poly(ionic liquid)s (PILs) has been investigated. Results showed that polymerizations of ChMA/NTf2− proceeded with higher rate in comparison to ChMA/Cl− one independently on the predetermined topologies (linear and four‐arm star‐shaped). From thermodynamical point of view, the glass transition temperature Tg increased with molecular weight Mn for linear‐ and star‐shaped PILs for both types of counterion. In addition, star‐shaped polymers of comparable Mn to linear ones were characterized by slightly higher Tg values. The resulting polyelectrolytes, after modification via exchange of Cl− anions to NTf2− ones were characterized by much higher Tg in comparison to those produced by direct polymerization of ionic monomer, indicating the crucial role of postpolymerization modification on thermodynamical properties of PILs. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2681–2691

Controllable Homogeneity/Heterogeneity Switch of Imidazolium Ionic Liquids for CO2 Utilization

AbstractImidazolium ionic liquids (IL) have been recognized as a promising platform for CO2 capture and conversion owing to the structural designability through molecular combination of cationic substituents and counter anions. However, the conventional homogeneous catalysis with ILs accompanies a laborious work‐up procedure to recycle the catalyst and purify product after the reaction, limiting the applicability of ILs. Herein, we optimize the molecular structure of imidazolium ILs to mediate the cycloaddition of CO2 upon epoxides, in which the IL functions as a homogeneous catalyst but exhibits heterogeneous separation capability. By varying the length of alkyl substituent on the imidazolium ring, the conversion efficiency of the epoxide into cyclic carbonate could be accelerated owing to higher reactivity of anions with longer aliphatic chains. The conversion efficiency was further optimized by having a proper type of counter anions with suitable level of nucleophilicity. The long‐chain IL exhibited temperature‐responsive phase transition behavior, allowing a facile isolation of IL and products after the reaction. In addition, with the high purity of obtained cyclic carbonates, non‐isocyanate poly(hydroxylurethane)s could be produced by polyaddition of diamines, promoting the utilization of CO2 as a chemical building block.