Changes In Ionic Conductivity Research Articles

Claudin-2-mediated cation and water transport share a common pore.

Claudin-2 is a tight junction protein typically located in 'leaky' epithelia exhibiting large paracellular permeabilities like small intestine and proximal kidney tubule. Former studies revealed that claudin-2 forms paracellular channels for small cations like sodium and potassium and also paracellular channels for water. This study analyses whether the diffusive transport of sodium and water occurs through a common pore of the claudin-2 channel. Wild-type claudin-2 and different claudin-2 mutants were expressed in MDCK I kidney tubule cells using an inducible system. Ion and water permeability and the effect of blocking reagents on both were investigated on different clones of the mutants. Neutralization of a negatively charged cation interaction site in the pore with the mutation, D65N, decreased both sodium permeability and water permeability. Claudin-2 mutants (I66C and S68C) with substitution of the pore-lining amino acids with cysteine were used to test the effect of steric blocking of the claudin-2 pore by thiol-reactive reagents. Addition of thiol-reactive reagents to these mutants simultaneously decreased conductance and water permeability. Remarkably, all experimental perturbations caused parallel changes in ion conductance and water permeability, disproving different or independent passage pathways. Our results indicate that claudin-2-mediated cation and water transport are frictionally coupled and share a common pore. This pore is lined and determined in permeability by amino acid residues of the first extracellular loop of claudin-2.

Enhanced Monitoring of Nanosecond Electric Pulse-Evoked Membrane Conductance Changes in Whole-Cell Patch Clamp Experiments.

Patch clamp electrophysiology serves as a powerful method for studying changes in plasma membrane ion conductance induced by externally applied high-intensity nanosecond electric pulses (NEPs). This paper describes an enhanced monitoring technique that minimizes the length of time between pulse exposure and data recording in a patch-clamped excitable cell. Whole-cell membrane currents were continuously recorded up to 11ms before and resumed 8ms after delivery of a 5-ns, 6MV/m pulse by a pair of tungsten rod electrodes to a patched adrenal chromaffin cell maintained at a holding potential of -70mV. This timing was achieved by two sets of relay switches. One set was used to disconnect the patch pipette electrode from the pre-amplifier and connect it to a battery to maintain membrane potential at -70mV, and also to disconnect the reference electrode from the amplifier. The other set was used to disconnect the electrodes from the pulse generator until the time of NEP/sham exposure. The sequence and timing of both sets of relays were computer-controlled. Using this procedure, we observed that a 5-ns pulse induced an instantaneous inward current that decayed exponentially over the course of several minutes, that a second pulse induced a similar response, and that the current was carried, at least in part, by Na+. This approach for characterizing ion conductance changes in an excitable cell in response to NEPs will yield information essential for assessing the potential use of NEP stimulation for therapeutic applications.

A single cation or anion dendrimer-based liquid electrolyte.

We propose here a novel liquid dendrimer-based single ion conductor as a potential alternative to conventional molecular liquid solvent-salt solutions in rechargeable batteries, sensors and actuators. A specific change from ester (-COOR) to cyano (-CN) terminated peripheral groups in generation-one poly(propyl ether imine) (G1-PETIM)-lithium salt complexes results in a remarkable switchover from a high cation (tLi+ = 0.9 for -COOR) to a high anion (tPF6- = 0.8 for -CN) transference number. This observed switchover draws an interesting analogy with the concept of heterogeneous doping, applied successfully to account for similar changes in ionic conductivity arising out of dispersion of insulator particle inclusions in weak inorganic solid electrolytes. The change in peripheral group simultaneously affects the effective ionic conductivity, with the room temperature ionic conductivity of PETIM-CN (1.9 × 10-5 Ω-1 cm-1) being an order of magnitude higher than PETIM-COOR (1.9 × 10-6 Ω-1 cm-1). Notably, no significant changes are observed in the lithium mobility even following changes in viscosity due to the change in the peripheral group. Changes in the peripheral chemical functionality directly influence the anion mobility, being lower in PETIM-COOR than in PETIM-CN, which ultimately becomes the sole parameter controlling the effective transport and electrochemical properties of the dendrimer electrolytes.

Migraine and epilepsy: what value today?

More than 100 years of investigation have found that seizures and migraine co-occur in some affected individuals and families, and there is much evidence that these diseases share genetic susceptibility. In particular, in a recent review, the prevalence of migraine in epileptic patients was about 12%[1]. On the other hand, epilepsy exhibits a prevalence of about 6% in migraineurs[2]. Moreover, epilepsy has also been reported in patients with familial hemiplegic migraine (FHM). Although few studies showed a prevalence of epilepsy of about 7% in FHM, currently no conclusive data are available. Certainly, epilepsy and migraine share common characteristics that the underlying pathophysiology relates to alterations in ion channels or ion transporters. In these episodic functional diseases, in which susceptible brain regions are hyperexcitable, the attacks begin with hypersynchronous neuronal firing[3]. In epilepsy, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors play a predominant role in mediating the generation and spread of seizure activity whereas in migraine mainly N-methyl-D-aspartate (NMDA) receptors are involved in triggering CSD. However, the nature of the ionic conductance changes leading to the massive but transitory neuronal depolarization underlying CSD has not yet been define[4]. Genetically determined dysfunction of ion transporters seems to point at a common underlying mechanism for both paroxysmal disorders. In the last two decades the mutations in the ion transportation genes CACNA1A, ATP1A2 and SCN1A have been identified for FHM. Conversely, only a few CACNA1A and ATP1A2 mutations have been reported in patients with sporadic hemiplegic migraine (SHM). These cases can be caused by a de novo mutation or by inheritance of a gene mutation from asymptomatic carrier and are usually characterized by early-onset, severe and complex disorders. Certainly, genetic analysis can provide greater insight into the potential causes of both disorders and it could contribute to better treatment choices.

The phase diagram of high-pressure superionic ice

Superionic ice is a special group of ice phases at high temperature and pressure, which may exist in ice-rich planets and exoplanets. In superionic ice liquid hydrogen coexists with a crystalline oxygen sublattice. At high pressures, the properties of superionic ice are largely unknown. Here we report evidence that from 280 GPa to 1.3 TPa, there are several competing phases within the close-packed oxygen sublattice. At even higher pressure, the close-packed structure of the oxygen sublattice becomes unstable to a new unusual superionic phase in which the oxygen sublattice takes the P21/c symmetry. We also discover that higher pressure phases have lower transition temperatures. The diffusive hydrogen in the P21/c superionic phase shows strong anisotropic behaviour and forms a quasi-two-dimensional liquid. The ionic conductivity changes abruptly in the solid to close-packed superionic phase transition, but continuously in the solid to P21/c superionic phase transition.

Up and down translocation events and electric double-layer formation inside solid-state nanopores.

We present a theoretical study of nanorod translocation events through solid-state nanopores of different sizes which result in positive or negative ion conductance changes. Using theoretical models, we show that positive conductance changes or up events happen for nanopore diameters smaller than a transition diameter dt, and negative conductance changes or down events occur for nanopore diameters larger than dt. We investigate the underlying physics of such translocation phenomena and describe the significance of the electric double-layer effects for nanopores with small diameters. Furthermore, for nanopores with large diameters, it is shown that a geometric model, formulated based on the nanoparticle blockade inside the nanopore, provides a straightforward and reasonably accurate prediction of ion conductance change. Based on this concept, we also implement a method to distinguish and detect nanorods of different sizes by focusing solely on the sign and not the exact value of the conductance change.

Statistical Analysis of Salt Deposition inside PEFC GDL from X-Ray Tomography

X-ray Computed Tomography (XCT) has been utilized extensively in the past decade to examine the internal features of PEMFC components, including extensive examination of the GDL structure [1-3]. Through the use of optics, micro-scale (and nano-scale) resolution has been achieved allowing for investigation of GDL’s, MPL’s and MEA’s for both in-situ [2] and ex-situ[1,3] studies without the need to cut into and damage the sample to obtain internal views. Published research with respect to GDL’s has produced information ranging from porosity distributions [1] and transport properties[3] to liquid water distribution inside the pores [2,3]. This study examines the salt deposition within a PEMFC cathode GDL using micro-XCT. The GDL in question came from a cell which was run on air that contained a calcium sulfate impurity[4]. Following a break-in period of 24 hours, a nebulizer was used to inject calcium sulfate solution (in DI water) at a 5 ppm concentration (based on dry air flow rate) into the cathode air stream. Galvanostatic performance data was recorded at 200mA/cm2, which showed a steady voltage loss rate more than 10 times compared to a non-contaminated baseline cell. During this time, salt deposits began to build up within the GDL and flow channels. This salt build up, combined with ionic conductivity changes in the CCL and changes in flooding behavior eventually led to the end of the experiment, because the cell was unable to hold the 200mA/cm2 [4]. Following the experiment, the cell was disassembled and components separated. At this time, the salt build up on the GDL surface and on the gas flow channels was visually observed to block the air flow pathways. Tomographies of the salt deposited GDL were obtained in three regions: a) near the inlet b) near the center c) and near the outlet. The resulting tomographies are provided in the 3D images presented in Figure 1. These tomographs show the different deposition patterns through the cell. Near the inlet, where the highest amount of water is produced, salt deposition appears to be uniformly distributed with no preferential nucleation site. Alternatively, near the center and the exit of the cell, the salt deposits in and on the GDL follow a distinct precipitation pattern, which are characterized by salt deposits with a crystalline structure that have the potential to grow out of the GDL. These deposits were observed as the flow channel obstructions that contributed to the end of the experiment. Through close examination of the 3D reconstruction (and shown in Figure 1), it is seen that in the center and exit regions of the GDL, most of the salt deposition appears to be flush with the GDL surface, which indicates that salt precipitates appear to be restricted from growing in that direction (out of the GDL), which provides evidence that salts nucleate under the lands (ribs). These salt crystals then have the ability to grow in the in-plane direction and out from under the lands (ribs) where salts can grow unrestricted out of the GDL and into the flow channel grooves. This process is in good agreement with the conclusions presented by Wang et al.[4], that low water concentrations under the flow channel ribs precipitates the formation of salt deposits. Statistical analysis is performed on the exported salt deposited GDL tomographs to examine the changes in void space (porosity) within the GDL in the through-plane direction. As salts appear to nucleate under the lands, this examination of the deposition profiles is presented for both regions of salt build up under the grooves and under the lands (ribs). These results are extended to comment on the changes to porosity under cell compression. Finally, we examine the effect of salt contaminant concentration and cell operating current on the salt precipitation patterns.

Variability in State-Dependent Plasticity of Intrinsic Properties during Cell-Autonomous Self-Regulation of Calcium Homeostasis in Hippocampal Model Neurons

How do neurons reconcile the maintenance of calcium homeostasis with perpetual switches in patterns of afferent activity? Here, we assessed state-dependent evolution of calcium homeostasis in a population of hippocampal pyramidal neuron models, through an adaptation of a recent study on stomatogastric ganglion neurons. Calcium homeostasis was set to emerge through cell-autonomous updates to 12 ionic conductances, responding to different types of synaptically driven afferent activity. We first assessed the impact of theta-frequency inputs on the evolution of ionic conductances toward maintenance of calcium homeostasis. Although calcium homeostasis emerged efficaciously across all models in the population, disparate changes in ionic conductances that mediated this emergence resulted in variable plasticity to several intrinsic properties, also manifesting as significant differences in firing responses across models. Assessing the sensitivity of this form of plasticity, we noted that intrinsic neuronal properties and the firing response were sensitive to the target calcium concentration and to the strength and frequency of afferent activity. Next, we studied the evolution of calcium homeostasis when afferent activity was switched, in different temporal sequences, between two behaviorally distinct types of activity: theta-frequency inputs and sharp-wave ripples riding on largely silent periods. We found that the conductance values, intrinsic properties, and firing response of neurons exhibited differential robustness to an intervening switch in the type of afferent activity. These results unveil critical dissociations between different forms of homeostasis, and call for a systematic evaluation of the impact of state-dependent switches in afferent activity on neuronal intrinsic properties during neural coding and homeostasis.

DNA Translocation in Nanometer Thick Silicon Nanopores.

Solid-state nanopores are single-molecule sensors that detect changes in ionic conductance (ΔG) when individual molecules pass through them. Producing high signal-to-noise ratio for the measurement of molecular structure in applications such as DNA sequencing requires low noise and large ΔG. The latter is achieved by reducing the nanopore diameter and membrane thickness. While the minimum diameter is limited by the molecule size, the membrane thickness is constrained by material properties. We use molecular dynamics simulations to determine the theoretical thickness limit of amorphous Si membranes to be ∼1 nm, and we designed an electron-irradiation-based thinning method to reach that limit and drill nanopores in the thinned regions. Double-stranded DNA translocations through these nanopores (down to 1.4 nm in thickness and 2.5 nm in diameter) provide the intrinsic ionic conductance detection limit in Si-based nanopores. In this regime, where the access resistance is comparable to the nanopore resistance, we observe the appearance of two conductance levels during molecule translocation. Considering the overall performance of Si-based nanopores, our work highlights their potential as a leading material for sequencing applications.

Involvement of membrane proteins and ion channels on the self-rotation of human cells in a non-rotating AC electric field.

Dielectrophoresis is a force that has been exploited in microsystems for label-free characterization and separation of cells, when their electrical signature is known. However, the polarization effect of cells at the transmembrane protein level is not well established. In this work, we have use the self-rotation effect of cells in a non-rotating field, known as the "Quincke effect," in order to measure the maximum rotation frequency (frotmax ) of different cell populations when modifying the composition of their membrane. We investigated the influence of active ionic transportation of membrane protein concentration on frotmax of HEK cells. Our results show that ionic transportation is responsible for the reduction of conductivity within the cytoplasm, which results in higher frotmax . However, the influence of the concentration of proteins in the membrane, achieved by silencing gene expression in cancer cells, changes significantly frotmax , which is not explained by the changes of ionic conductivity within the cell.

Synthesis and performance of novel anion exchange membranes based on imidazolium ionic liquids for alkaline fuel cell applications

Novel anion exchange membranes (AEMs) based on two types of imidazolium ionic liquids, 1-vinyl-3-methylimidazolium iodide [VMI]I and 1-vinyl-3-butylimidazolium bromide [VBI]Br, have been synthesized by copolymerization. The obtained membranes are characterized in terms of water uptake, ion exchange capacity (IEC), ionic conductivity as well as thermal and chemical stability. The conductivity reaches 0.0226 Scm−1 at 30 °C. All the membranes show excellent thermostability. The membranes are stable in 10 mol L−1 NaOH solution at 60 °C for 120 h without obvious changes in ion conductivity. Fuel cell performance using the resulting membrane has been investigated. The open circuit voltage (OCV) of the H2/O2 fuel cell is 1.07 V. A peek power density of 116 mW cm−2 is obtained at a current density of 230 mA cm−2 at 60 °C. The results demonstrate the brilliant prospect of the developed membranes for alkaline fuel cell applications.

Systematic Analysis of Cation Stability in Alkaline Exchange Membrane Fuel Cells

Discovery and implementation of alternative energy resources have been a leading R&D task for several decades. Of the clean energy technologies, fuel cells offer a viable option because they can efficiently convert the chemical energy stored in fuels directly into electrical energy without emission of harmful pollutants. In recent years anion exchange membrane (AEM) fuel cells [in which a solid polymer electrolyte containing fixed cationic groups facilitates the transport of OH-anions] have received increased attention owing to their unique advantages over proton exchange membrane fuel cells. Some of the advantages include the use of low-cost non-precious metal catalysts, faster cathode reaction rates, and greater fuel flexibility with lower fuel crossover [1].Currently the most challenging technical hurdle for the implementation of AEM fuel cells is the lack of membrane materials that are stable under high pH conditions. Recently it has been discovered that polymers which include aromatic rings linked via ether bonds degrade in high alkaline environments [2],[3]. And among the various cationic species (such as sulfonium, phosphonium, imidazolium, and guanidinium), benzyltrimethylammonium is the most frequently adopted cation because of its simple preparation and reasonable thermal and chemical stability. However, more robust cations are still needed for long-term uses in alkaline conditions.Although AEM chemical degradation has been widely acknowledged, a systematic study on the stability of various cations has yet to be reported. The majority of AEM stability reports study chemical degradation of the cationic species that are tethered to a polymer backbone and compare their stability based on changes in ion-exchange capacity and ionic conductivity as a function of time from exposure to various concentrations of hydroxide solution. This approach creates inconsistencies in comparing cation degradation since different testing conditions are frequently used and the polymer backbones may affect the overall AEM stability.Herein, we report a convenient way to systematically compare the chemical stability of various cation species. We prepared a series of small molecule quaternary ammonium analogues in pure hydroxide form by conducting ion exchange reactions with silver oxide (Ag2O) and quantitatively monitored their stability in D2O via NMR spectroscopy. By using small molecules for our degradation analysis, we were able to avoid inconsistencies previously faced in polymer-based studies. With this approach we identified several quaternized ammonium cations that are more stable than benzyltrimethylammonium; of which some of them show minimal degradation even above 100 oC for an extended time period. This simple test of small molecule analysis can provide the most optimal solution for predicting which cation structures may have high stability when later attached to the polymer backbone.

Dehydration and decomposition behavior of the NaH2(PO4)0,48AsO4)0,52.H2O compound in the temperature range from 253 K to 333 K.

The mixed compound NaH2(PO4)0.48(AsO4)0.52.H2O, which has been examined by Raman spectroscopy, XRD powder and dielectric, exhibits solid–solid phase transitions and one reversible solid–liquid phase transition. Besides, the investigation of dehydration behavior of sodium dihydrogenate phosphate-arsenate monohydrate was undertaken in a temperature range from 253 K to 333 K. The onset temperature of dehydration was determined from changes in ionic conductivity and X-ray powder on heating. It was confirmed by the Raman study not only in the disappearance of the vibrations assigned to the PO4, AsO4 but also in the appearance of the new vibrations attributed to the (PO3), which constitutes the P-O-P chain, giving a polymer with the formula: NaH2(P2O7)x(As2O7)(1-x). The important variation was observed in all studies at 313 K, which could correspond to the transformation of the NDAP compounds of a solid crystal into a liquid form.

DETECTION OF DISTINCT PATHOLOGICAL TAU CONFORMATIONS IN CSF OF PATIENTS WITH NEURODEGENERATIVE DISEASES

pharmacological agent used in the study is a proprietary and experimental compound provided by Neuropore Therapies Inc. (La Jolla, CA). Results: Short pre-incubation (w10min) of the compoundwith Ab(1-42) effectively prevented ion channel conductance (Figure C). However, the compound added along with A b(1-42) showed no change in ionic conductance (Figure B) vs. the control with A b(1-42) alone (Figure A), even at much higher compound concentrations. Conclusions: The need for pre-incubation, even at high compound concentrations, has led to two conclusions with regards to A b(1-42) toxicity: 1) the peptide inserts quickly into the membrane where it is shielded from the action of the compound. 2) A conformational change is likely induced during the incubation. A b forms b-sheet secondary structure and disruption of the b structure could prevent membrane insertion, channel formation, or induce a collapsed pore. Prior work with Ab containing a point substituted proline (a known b -sheet breaker) showed channel structure by AFMbut did not demonstrate ionic conductance. Taken together, the studies suggest that b -sheet structure is necessary for toxic conductance through A b channels.

AMYLOID ION CHANNEL TOXICITY: DISRUPTION OF B-SHEET STRUCTURE PREVENTS TOXIC IONIC FLUX THROUGH AB PORES

A common mechanism underlying Alzheimer's disease (AD) pathophysiology relies upon increased levels of soluble amyloid-beta (Aβ) oligomers. These oligomers induce uncontrolled ion flux across cellular membranes resulting in the dysregulation of ionic homeostasis, particularly calcium ions. High calcium concentration is known to cause neuronal degeneration and death that might underlie AD cognitive impairment. Previous 3D structural analysis, using atomic force microscopy (AFM), in our laboratory has shown that Aβ forms multi-subunit ion channels (Figure A, inset). These ion channel structures are complemented by the expected ionic permeability and single channel conductance of calcium and other cations in purified bilayer preparations. Amyloid ion channel structure-activity relationships are tightly interlinked; pharmacological and small molecule interventions that modulate channel structure could be then become an effective strategy to prevent their toxic activity. In this study, we examined pharmacologic intervention in reducing ionic flux through A β ion channels. Aβ(1-42) ion channels were reconstituted in planar lipid bilayers (PLB) and electrical conductance recordings were analyzed both in the presence as well as in the absence of a defined pharmacological agent. The pharmacological agent used in the study is a proprietary and experimental compound provided by Neuropore Therapies Inc. (La Jolla, CA). Short pre-incubation (∼10 min) of the compound with Aβ(1-42) effectively prevented ion channel conductance (Figure C). However, the compound added along with A β(1-42) showed no change in ionic conductance (Figure B) vs. the control with A β(1-42) alone (Figure A), even at much higher compound concentrations.

Redox Regulation of Ion Channels in the Pulmonary Circulation

Significance: The pulmonary circulation is a low-pressure, low-resistance, highly compliant vasculature. In contrast to the systemic circulation, it is not primarily regulated by a central nervous control mechanism. The regulation of resting membrane potential due to ion channels is of integral importance in the physiology and pathophysiology of the pulmonary vasculature. Recent Advances: Redox-driven ion conductance changes initiated by direct oxidation, nitration, and S-nitrosylation of the cysteine thiols and indirect phosphorylation of the threonine and serine residues directly affect pulmonary vascular tone. Critical Issues: Molecular mechanisms of changes in ion channel conductance, especially the identification of the sites of action, are still not fully elucidated. Future Directions: Further investigation of the interaction between redox status and ion channel gating, especially the physiological significance of S-glutathionylation and S-nitrosylation, could result in a better understanding of the physiological and pathophysiological importance of these mediators in general and the implications of such modifications in cellular functions and related diseases and their importance for targeted treatment strategies. Antioxid. Redox Signal. 22, 465–485.

Effect of concentration gradient on ionic current rectification in polyethyleneimine modified glass nano-pipettes

Ion current rectification dependent on the concentration gradient of KCl solutions was systematically investigated in polyethyleneimine modified glass nano-pipettes with inner diameter of 105 nm. Peak shape dependence of the rectification factor on outer KCl solution concentration was observed when inner KCl solution with concentration from 1 mM to 500 mM was used. The peak shape dependence was also observed when the concentrations of the inner and outer KCl solutions were identically controlled. The peak shape in the ion current rectification could be explained by the ion conductance changes through the conical nano-pipette, which result from modulation of ion concentration.

Dopaminergic tone persistently regulates voltage-gated ion current densities through the D1R-PKA axis, RNA polymerase II transcription, RNAi, mTORC1, and translation

Long-term intrinsic and synaptic plasticity must be coordinated to ensure stability and flexibility in neuronal circuits. Coordination might be achieved through shared transduction components. Dopamine (DA) is a well-established participant in many forms of long-term synaptic plasticity. Recent work indicates that DA is also involved in both activity-dependent and -independent forms of long-term intrinsic plasticity. We previously examined DA-enabled long-term intrinsic plasticity in a single identified neuron. The lateral pyloric (LP) neuron is a component of the pyloric network in the crustacean stomatogastric nervous system (STNS). LP expresses type 1 DA receptors (D1Rs). A 1 h bath application of 5 nM DA followed by washout produced a significant increase in the maximal conductance (Gmax) of the LP transient potassium current (IA) that peaked ~4 h after the start of DA application; furthermore, if a change in neuronal activity accompanied the DA application, then a persistent increase in the LP hyperpolarization activated current (Ih) was also observed. Here, we repeated these experiments with pharmacological and peptide inhibitors to determine the cellular processes and signaling proteins involved. We discovered that the persistent, DA-induced activity-independent (IA) and activity-dependent (Ih) changes in ionic conductances depended upon many of the same elements that enable long-term synaptic plasticity, including: the D1R-protein kinase A (PKA) axis, RNA polymerase II transcription, RNA interference (RNAi), and mechanistic target of rapamycin (mTOR)-dependent translation. We interpret the data to mean that increasing the tonic DA concentration enhances expression of a microRNA(s) (miRs), resulting in increased cap-dependent translation of an unidentified protein(s).

Proton Conductive Areas on Sulfonated Poly(Arylene Ketone) Multiblock Copolymer Electrolyte Membrane Studied by Current-Sensing Atomic Force Microscopy

Proton conductive spots on the membrane surface of sulfonated poly(arylene ketone) multiblock copolymer were investigated by current-sensing atomic force microscopy (CS-AFM) under the hydrogen atmosphere with changing relative humidity, temperature, and bias voltage. The bright spots, where the hydrophilic clusters should be effectively connected inside the membrane, were distributed rather inhomogeneously on the surface at low temperature and humidity but became more homogeneous at higher temperature and humidity. The average diameter of the spots was approximately 10 nm at 40% RH, which increased to 13 nm at 70% RH. The total area of the proton conducting spots, as well as current at each spot, on the membrane surface increased at high humidity and temperature. In addition, the diameter of the proton-conductive spots and the ratio of proton-conductive area on the membrane surface continuously increased with increasing the bias voltage. This increase of the conducting area and the current should be related to the change of the bulk ionic conductivity.

Properties of gel electrolytes based on PVdF/HFP containing anion receptors

This work concerns systems utilizing gel electrolytes based on PVdF/HFP, containing a supramolecular compound additive. Supramolecular compounds are one of the many types of additives, and among them – anion receptors. Solutions of 1 M LiClO4 or 1 M LiBF4 in solvent: PC, PC/EC mixture (1:1), PC/DEC mixture (1:1) or EC/DEC mixture (1:1), were the liquid electrolyte encapsulated in a polymer membrane. N-[2-[Bis[2-N′-(3-pyridyl)ureido]ethyl]-amino]ethyl]-N′-(3-pyridyl)urea was applied as the supramolecular compound – anion receptor. Content of the receptor varied from 5 to 20 mmol in 10 cm3 of 1 M lithium salt solutions. Changes in ionic conductivity and the stability of gel electrolytes – lithium electrode interface, were analyzed on the basis of impedance spectroscopy technique in Swagelok geometry. Lithium transference number was calculated for some of the studied gels using the polarization method. Finally, thermal stability of the systems studied was determined by means of DSC technique.