Polymer‐in‐ionic‐liquid electrolytes

In order to achieve high conductivity in a polymer electrolyte, polymer‐in‐ionic‐liquid electrolytes have been explored. It is found in this study that poly[vinylpyrrolidone‐co‐(vinyl acetate)] (P(VP‐c‐VA)) in 1‐ethyl‐3‐methylimidazolium bis(trifluoromethyl sulfonyl) amide (EtMeIm⁺Tf₂N⁻) and poly(N,N‐dimethyl acrylamide) (PDMAA) in trimethyl butyl ammonium bis(trifluoromethane sulfonyl) amide (N₁₁₁₄⁺Tf₂N⁻) produce ion‐conducting liquids and gels. The P(VP‐c‐VA)/ EtMeIm⁺Tf₂N⁻ mixture has a conductivity around 10⁻³ S · cm⁻¹ at 22 °C, for copolymer concentrations up to 30 wt.‐%. Thermal analysis shows that the T_g of the P(VP‐c‐VA)/ EtMeIm⁺Tf₂N⁻ system is well described by the Fox equation as a function of polymer content. Poly(methyl methacrylate) (PMMA)/ EtMeIm⁺Tf₂N⁻ gel electrolytes were prepared by in‐situ polymerisation of the monomer in the ionic liquid. In the presence of 0.5–2.0 wt.‐% of a crosslinking agent, these PMMA‐based electrolytes displayed elastomeric properties and high conductivity (ca. 10⁻³ S · cm⁻¹) at room temperature.

Conductivity versus temperature in crosslinked PMMA/ EtMeIm⁺Tf₂N⁻ gel electrolytes with different concentrations of crosslinking agent.     

Polyurethanes Containing an Imidazolium Diol‐Based Ionic‐Liquid Chain Extender for Incorporation of Ionic‐Liquid Electrolytes

Novel polyurethane (PU) cationomers are synthesized using an imidazolium diol‐based ionic liquid (IL) chain extender. A systematic comparison with a non‐ionic PU analogue reveals effect of the imidazolium cation on physical properties, hydrogen bonding, and morphology of segmented PU. Casting resulting PU solutions with various contents of IL generates novel membranes. Thermal study reveals that IL‐containing PU membranes exhibit a constant soft segment T_g at ?81 °C; however, the T_g of imidazolium hard segments systematically shifts to lower temperatures with increasing IL content. This suggests that IL preferentially locates into the imidazolium ionic hard domains, which is also evident in small‐angle X‐ray scattering. Moreover, dielectric relaxation spectroscopy demonstrates increased ionic conductivity of PU membranes by 5 orders of magnitude upon incorporation of 30 wt% IL.

     

Water‐Soluble Conjugated Polyelectrolyte‐Based Fluorescence Enzyme Coupling Protocol for Continuous and Sensitive β‐Galactosidase Detection

A simple, rapid, continuous and homogeneous fluorescent assay for β‐galactosidase was developed, combining an enzyme‐coupled reaction and signal amplification property of conjugated polyelectrolytes (CPs). The procedure is based on a sequence of two coupled biocatalytic steps in which the β‐galactosidase hydrolyzes its substrate to a phenol derivative followed by conversion to quinone (secondary product) with fluorescence quenching ability by the tyrosinase. The fluorescence of PFP?SO is efficiently quenched by the quinone via an electron transfer process. The limit of detection (LOD) of this assay is less than 0.0005 U · mL^?1, which is better than that of electrochemical method and is comparable to that of most sensitive chemiluminescent techniques. In principle, this sensor mechanism will extend the application window of CPs for wide‐spectrum enzyme detections. This “mix‐and‐detect” approach could be expanded to a high‐throughput manner.

     

Cationic Main‐Chain Polyelectrolytes with Pyridinium‐Based p‐Phenylenevinylene Units and Their Aggregation‐Induced Gelation

Cationic polyelectrolytes find potential applications in electronic device fabrication, biosensing as well as in biological fields. Herein, a series of cationic main‐chain polyelectrolytes with pyridinium‐based p ‐phenylenevinylene units that are connected via alkylene spacers of varying lengths are synthesized by a base‐catalyzed aldol‐type coupling reaction. Their mean average molecular weights range from 15 000 to 32 000 g mol^‐1, corresponding to about 16–33 repeat units. Due to the presence of alkyl side‐chains and alkylene spacers as well as cationic hard‐charges the polymers are endowed with amphiphilic character and hence, aggregation of these polyelectrolytes at high concentration leads to thermoreversible physical gel formation in dimethyl sulfoxide accompanied by interchain interactions. Morphological analysis shows spherical aggregates in case of C₁₆‐Poly‐S₁₂ in dimethyl sulfoxide. Dependence of gelation behavior on the length of alkyl side‐chains and alkylene spacers of the polyelectrolytes are addressed.

     

Proton‐Conducting Properties of Acid‐Doped Poly(glycidyl methacrylate)‐1,2,4‐Triazole Systems

1,2,4‐triazole‐functional PGMA polymers have been synthesized and their anhydrous proton‐conducting properties were investigated after doping with phosphoric acid and triflic acid. PGMA was prepared by solution polymerization and then modified with 1H‐1,2,4‐triazole (Tri) and 3‐amino‐1,2,4‐triazole (ATri). FT‐IR, ¹³C NMR and elemental analysis verify the high immobilization of the triazoles in the polymer chain. Phosphoric‐acid‐doped polymers showed lower T_g and higher proton conductivities. PGMA‐Tri 4 H₃PO₄ showed a maximum water‐free proton conductivity of approximately 10^?2 S · cm^?1 while that of PGMA‐ATri 2 H₃PO₄ was 10^?3 S · cm^?1. The structure and dynamics of the polymers were explored by ¹H MAS and ¹³C CP‐MAS solid‐state NMR.

     

Preparation of pH‐Responsive Hydrophilic Core‐Shell Particles for Encapsulation of Water‐Soluble Material

Dual pH‐responsive PAAc/ PVAm core‐shell particles to encapsulate water‐soluble material were prepared through the deposition of PVAm on the surface of PAAc core particles. The structural characteristics of the core‐shell particles were confirmed by SEM and CLSM. To investigate the release profiles of the core‐shell particles and PAAc core, methylene blue, which is a cationic water‐soluble dye, was introduced. Release profiles were dominantly affected by the core swelling behavior at different pH values. The release rate of the core‐shell was less than the PAAc core, indicating that it is affected by ionic interactions between the particle and the cationic dye.

     

Well‐Defined Imidazolium ABA Triblock Copolymers as Ionic‐Liquid‐Containing Electroactive Membranes

Nitroxide‐mediated polymerization (NMP) affords the synthesis of well‐defined ABA triblock copolymers with polystyrene external blocks and a charged poly(1‐methyl‐3‐(4‐vinylbenzyl)­imidazolium bis(trifluoromethane sulfonyl)imide central block. Aqueous size‐exclusion chromatography (SEC) and ¹H NMR spectroscopy studies confirm the control of the composition and block lengths for both the central and external blocks. Dynamic mechanical analysis (DMA) reveals a room temperature modulus suitable for fabricating these triblock copolymers into electroactive devices in the presence of an added ionic liquid. Dielectric relaxation spectroscopy (DRS) elucidates the ion‐transport properties of the ABA triblock copolymers with varied compositions. The ionic conductivity in these single‐ion conductors exhibits Vogel–Fulcher–Tammann (VFT) and Arrhenius temperature dependences, and electrode polarization (EP) analysis determines the number density of simultaneously conducting ions and their mobility. The actuators derived from these triblock copolymer membranes experience similar actuation speeds at an applied voltage of 4 V DC, as compared with benchmark Nafion membranes. These tailorable ABA block copolymers are promising candidates for ionic‐polymer device applications.

     

Synthesis and Properties of Side‐Chain Liquid Crystalline Polypeptides Bearing Various Alkyl Spacers and Oligo‐Ethylene‐Glycol Tails

A series of polypeptides bearing various alkyl (i.e., propyl, hexyl, or octyl) spacers, biphenyl mesogens, and oligo‐ethylene‐glycol (OEG) tails (i.e., PPLG₂₆‐BPOEG _m, PHLG₃₄‐BPOEG_m, and POLG₃₂‐BPOEG_m [m = 3 or 7]) has been synthesized via 1,3‐dipolar cycloaddition reactions with quantitative grafting densities. Fourier transform infrared results reveal that the polypeptides adopted an α‐helical conformation in the solid‐state. Differential scanning calorimetry (DSC) analysis reveals that the glass transition temperatures (T_gs) of the polypeptides with OEG₃ tails decrease with the increasing length of the alkyl spacers. For the samples containing alkyl spacers of the same length, T_g significantly decreases with the increasing lengths of the OEG tails. Polarized optical microscope (POM) results reveal that all polypeptides exhibit strong birefringence at room temperature. Polypeptides with long alkyl spacers (i.e., hexyl or octyl) or OEG₇ tails show isotropic transitions, while PPLG₂₆‐BPOEG₃ show no clear point temperature before thermal decomposition. DSC, POM, and wide‐angle X‐ray scattering results collectively reveal that polypeptides with long alkyl spacers (i.e., hexyl or octyl) and OEG₃ tails undergo a reversible smectic E phase to isotropic phase transition, while polypeptides with OEG₇ tails undergo a reversible liquid crystalline phase to isotropic phase transition. The transition temperatures increase with the increasing length of alkyl spacers.

     

Liquid Crystals Embedded in Polymeric Electrolytes for Quasi‐Solid State Dye‐Sensitized Solar Cell Applications

A new series of liquid crystal embedded in polymeric electrolytes was developed for obtaining high efficiency in quasi‐solid state dye‐sensitized solar cells (DSSCs). The polymeric electrolytes were composed of iodide and tri‐iodide redox species in polyacrylonitrile (PAN) as a polymer matrix and liquid crystals (E7 or ML‐0249) for increasing the order parameter of electrolyte components with easy transport of redox species. The highest efficiency (6.21 and 6.29% at 1 sun) was obtained for the quasi‐solid state DSSCs using E7 to PAN and ML‐0249 to PAN, respectively, under AM 1.5 G illumination and an aperture mask condition. The high efficiencies of the quasi‐solid state DSSCs are due to the effective formation of pathways through liquid crystal orientation for the transport of redox species.

     

Solid Polymer Electrolytes Based on Copolymers of Cyclic Carbonate Acrylate and n‐Butylacrylate

Solid polymer electrolytes (SPEs) are prepared by mixing poly(2‐oxo‐1,3‐dioxolan‐4‐yl)methyl acrylate‐random‐n‐butylacrylate) [P(cyCA‐r‐nBA)] statistical copolymers with bis(trifluoromethane)sulfonimide lithium salt. The P(cyCA‐r‐nBA) copolymers are synthesized by reversible addition‐fragmentation chain transfer polymerization and different molar masses as well as copolymer composition are targeted in order to study the influence of the molecular parameters on the thermal, mechanical, and electrochemical properties of the SPEs obtained after mixing the copolymers with lithium salts. In the investigated experimental window, it is shown that the thermal and mechanical properties of the SPEs mainly depend on the composition of the copolymer and are poorly influenced by the molar mass. In sharp contrast, the ionic conductivities are more deeply influenced by the molar mass than by the composition of the copolymers. In this respect ionic conductivity values ranging from 4.2 × 10^?6 S cm^?1 for the lower molar mass sample to 8 × 10^?8 S cm^?1 for the higher molar mass one are measured at room temperature for the investigated SPEs.     

EDC‐Mediated Grafting of Quaternary Ammonium Salts onto Chitosan for Antibacterial and Thermal Properties Improvement

The present study provides antibacterial and thermal improvements of chitosan‐based systems through chemical modification with different quaternary ammonium salts using 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide (EDC) as mediator. Three different ammonium salts with a carboxylic acid end group are synthesized through a quaternization reaction between bromohexanoic acid and the respective tertiary amines (quinoline, N,N‐dimethylbenzylamine and pyridine). They are then chemically grafted along the chitosan backbone using EDC as a carboxyl activating agent for the coupling with the primary amine groups. This allows three different chitosan derivatives to be obtained: Quinolinium‐Chitosan (QA‐Cs), Benzalkonium‐Chitosan (BK‐Cs), and Pyridinium‐Chitosan (PA‐Cs), respectively. The chemical structures are characterized by ¹H NMR analysis. The thermal stability is analyzed by thermogravimetric analysis. Antibacterial efficiencies of chitosan derivatives against Pseudomonas aeruginosa and Staphylococcus aureus strains are determined. All the chitosan derivatives show negligible antibacterial activity against Gram‐positive S. aureus strain. However, the antibacterial activity against Gram‐negative P. aeruginosa strain is significantly improved.     

Proton Conducting Copolymer Electrolytes Based on Vinyl Phosphonic Acid and 5‐(Methacrylamido)tetrazole

Copolymer electrolytes based on 5‐(methacrylamido)tetrazole (MTet) and vinyl phosphonic acid (VPA) are prepared. The obtained copolymers are analyzed by FTIR, ¹H NMR, ¹³C NMR, and ³¹P NMR spectroscopy, thermogravimetric analysis (TGA), differantial scanning calorimetry (DSC), energy dispersive X‐ray spectrometry (EDS), elemental analysis (EA), cyclic voltammetry (CV), and impedance spectroscopy. The morphology of the copolymers is characterized by X‐ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The highest proton conductivity is obtained as 0.01 S/cm at 150 °C and in anhydrous conditions.

     

A Facile Approach to Fabricate Self‐Standing Gel‐Polymer Electrolytes for Flexible Lithium‐Ion Batteries by Exploitation of UV‐Cured Trivalent/Monovalent Acrylate Polymer Matrices

A facile approach to fabricate a self‐standing GPE for flexible lithium‐ion batteries is demonstrated using a UV‐cured trivalent/monovalent acrylate polymer matrix and a liquid electrolyte. The polymer matrix is successfully synthesized with the co‐presence of the liquid electrolyte by UV polymerization of ETPTA, which has trivalent vinyl groups, and EGMEA, which contains monovalent vinyl groups, with the ETPTA/EGMEA ratio fixed at 90/10 (wt%/wt%). The ETPTA/EGMEA matrix shows a lower T_g than the ETPTA matrix alone, which helps improve the mechanical flexibility and ionic transport of the resulting GPE. These features of the ETPTA/EGMEA‐based GPE, together with its superior interfacial compatibility towards electrodes, play crucial roles in obtaining a better cell performance compared to the ETPTA‐based GPE.     

1,4‐Bisbenzil: Visible‐Light‐ and Heat‐Assisted Crosslinking of Polystyrene Films

Polystyrene (PS) film containing 1,4‐bisbenzil is efficiently crosslinked in two steps. In the first step, visible light (λ > 400 nm) causes molecular oxygen to insert between two carbonyl groups of one of the 1,2‐dicarbonyl groups. The peroxide is subsequently decomposed by absorption of another photon, forming acyloxy radicals, which add to the aromatic ring of the PS chain. The remaining 1,2‐dicarbonyl group is then photoperoxidized to form PS with pendant benzoyl peroxide moieties. In the second step, pendant benzoyl peroxide groups are decomposed thermally to form acyloxy macroradicals responsible for the crosslinking. Crosslinking proceeds simultaneously with degradation. Finally, the gel content in the film may exceed 80 wt%.

     

Liquid‐Glassy Polymer Diffusion: Effects of Liquid Molecular Weight and Temperature

We examine mechanistic aspects of the diffusion between a series of liquid polystyrenes (PS) and a glassy poly(phenylene oxide) (PPO) matrix, through the use of confocal Raman microspectroscopy. The results show that the diffusion kinetics has Fickean characteristics, similar to those found in liquid‐liquid polymer diffusion. No signatures of the linear regime typical of the case‐II diffusion mechanism were found. Overall, these observations are consistent with the claim that case‐II is unlikely to occur in liquid‐glassy polymer diffusion.

     

Reproducibility and optimization of in vivo human diffusion‐weighted MRS of the corpus callosum at 3T and 7T

Diffusion‐weighted MRS (DWS) of brain metabolites enables the study of cell‐specific alterations in tissue microstructure by probing the diffusion of intracellular metabolites. In particular, the diffusion properties of neuronal N‐acetylaspartate (NAA), typically co‐measured with N‐acetylaspartyl glutamate (NAAG) (NAA + NAAG = tNAA), have been shown to be sensitive to intraneuronal/axonal damage in pathologies such as stroke and multiple sclerosis. Lacking, so far, are empirical assessments of the reproducibility of DWS measures across time and subjects, as well as a systematic investigation of the optimal acquisition parameters for DWS experiments, both of which are sorely needed for clinical applications of the method. In this study, we acquired comprehensive single‐volume DWS datasets of the human corpus callosum at 3T and 7T. We investigated the inter‐ and intra‐subject variability of empirical and modeled diffusion properties of tNAA [D_avg(tNAA) and D_model(tNAA), respectively]. Subsequently, we used a jackknife‐like resampling approach to explore the variance of these properties in partial data subsets reflecting different total scan durations. The coefficients of variation (C_V) and repeatability coefficients (C_R) for D_avg(tNAA) and D_model(tNAA) were calculated for both 3T and 7T, with overall lower variability in the 7T results. Although this work is limited to the estimation of the diffusion properties in the corpus callosum, we show that a careful choice of diffusion‐weighting conditions at both field strengths allows the accurate measurement of tNAA diffusion properties in clinically relevant experimental time. Based on the resampling results, we suggest optimized acquisition schemes of 13‐min duration at 3T and 10‐min duration at 7T, whilst retaining low variability (C_V ≈ 8%) for the tNAA diffusion measures. Power calculations for the estimation of D_model(tNAA) and D_avg(tNAA) based on the suggested schemes show that less than 21 subjects per group are sufficient for the detection of a 10% effect between two groups in case–control studies. Copyright © 2015 John Wiley & Sons, Ltd.     

22‐S‐Hydroxycholesterol protects against ethanol‐induced liver injury by blocking the auto/paracrine activation of MCP‐1 mediated by LXRα

Chronic ethanol consumption causes hepatic steatosis and inflammation, which are associated with liver hypoxia. Monocyte chemoattractant protein‐1 (MCP‐1) is a hypoxia response factor that determines recruitment and activation of monocytes to the site of tissue injury. The level of MCP‐1 is elevated in the serum and liver of patients with alcoholic liver disease (ALD); however, the molecular details regarding the regulation of MCP‐1 expression are not yet understood completely. Here, we show the role of liver X receptor α (LXRα) in the regulation of MCP‐1 expression during the development of ethanol‐induced fatty liver injury, using an antagonist, 22‐S‐hydroxycholesterol (22‐S‐HC). First, administration of 22‐S‐HC attenuated the signs of liver injury with decreased levels of MCP‐1 and its receptor CCR2 in ethanol‐fed mice. Second, hypoxic conditions or treatment with the LXRα agonist GW3965 significantly induced the expression of MCP‐1, which was completely blocked by treatment with 22‐S‐HC or infection by shLXRα lentivirus in the primary hepatocytes. Third, over‐expression of LXRα or GW3965 treatment increased MCP‐1 promoter activity by increasing the binding of hypoxia‐inducible factor‐1α to the hypoxia response elements, together with LXRα. Finally, treatment with recombinant MCP‐1 increased the level of expression of LXRα and LXRα‐dependent lipid droplet accumulation in both hepatocytes and Kupffer cells. These data show that LXRα and its ligand‐induced up‐regulation of MCP‐1 and MCP‐1‐induced LXRα‐dependent lipogenesis play a key role in the autocrine and paracrine activation of MCP‐1 in the pathogenesis of alcoholic fatty liver disease, and that this activation may provide a promising new target for ALD therapy.Copyright © 2014 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.     

Characteristics of in‐vitro phenotypes of glutamic acid decarboxylase 65 autoantibodies in high‐titre individuals

Previous studies have indicated phenotypical differences in glutamic acid decarboxylase 65 autoantibodies (GADA) found in type 1 diabetes (T1D) patients, individuals at risk of developing T1D and stiff‐person syndrome (SPS) patients. In a Phase II trial using aluminium‐formulated GAD₆₅ (GAD‐alum) as an immunomodulator in T1D, several patients responded with high GADA titres after treatment, raising concerns as to whether GAD‐alum could induce GADA with SPS‐associated phenotypes. This study aimed to analyse GADA levels, immunoglobulin (Ig)G1–4 subclass frequencies, b78‐ and b96·11‐defined epitope distribution and GAD₆₅ enzyme activity in sera from four cohorts with very high GADA titres: T1D patients (n = 7), GAD‐alum‐treated T1D patients (n = 9), T1D high‐risk individuals (n = 6) and SPS patients (n = 12). SPS patients showed significantly higher GADA levels and inhibited the in‐vitro GAD₆₅ enzyme activity more strongly compared to the other groups. A higher binding frequency to the b78‐defined epitope was found in the SPS group compared to T1D and GAD‐alum individuals, whereas no differences were detected for the b96·11‐defined epitope. GADA IgG1–4 subclass levels did not differ between the groups, but SPS patients had higher IgG2 and lower IgG4 distribution more frequently. In conclusion, the in‐vitro GADA phenotypes from SPS patients differed from the T1D‐ and high‐risk groups, and GAD‐alum treatment did not induce SPS‐associated phenotypes. However, occasional overlap between the groups exists, and caution is indicated when drawing conclusions to health or disease status.