Changes In Ionic Conductivity Research Articles

A membrane-moderated, conductimetric sensor for the detection and measurement of specific organic solutes in aqueous solutions

A novel conductimetric sensor, capable of detecting and continuously monitoring the concentration of a specific nonionic microsolute (glucose) in a multicomponent aqueous solution (e.g., whole blood or plasma) is described, and preliminary experimental evidence supporting the validity of the sensor concept is presented. Detection is based upon the use of a glucose-selective complexing agent (a boronic acid immobilized in a hydrogel) which liberates a mobile microion (hydrogen ion) when it binds a glucose molecule. The change in ionic conductivity of the hydrogel resulting from the increase in ion concentration is thus directly related to the ambient glucose concentration. Confinement of the liberated ions within the hydrogel, and prevention of entry of extraneous electrolytes present in the test solution, is necessary to make the conductimetric measurement meaningful. This is achieved by encapsulating the hydrogel within a bipolar ion exchange membrane impermeable to ions but freely permeable to glucose (and other nonionic microsolutes). A physicochemical model of the complexation equilibrium, kinetics of solute transport through the membrane and hydrogel phase, and their impact upon the ionic conductivity of the hydrogel is presented, which supports the utility of this sensor concept as a potentially reliable and sensitive glucose monitor. Its generic utility for monitoring nonionic microsolutes in multicomponent aqueous solutions is suggested.

Transport Properties of Superionic Conducting Glasses (AgX)<SUB>0.4</SUB>(Ag<SUB>2</SUB>O)<SUB>0.3</SUB>(GeO<SUB>2</SUB>)<SUB>0.3</SUB> (X=I, Br, Cl)

In order to identify the dominant mechanism of ionic conduction, the electrical conductivity and ionic mobility of the glasses (AgX) 0.4 (Ag 2 O) 0.3 (GeO 2 ) 0.3 (X = I, Br, Cl) were measured separately in the temperature range from 293 to 393 K by coupling the AC technique with the TIC method. Electronic conductivity was also measured at 293 K by the Wagner polarization method. The total electrical conductivity of these glasses was found to be as high as 10 -1 Ω -1 m -1 , and the mobility about 10 -6 m 2 V -1 s -1 . The variation of total electrical conductivity and mobility at constant temperature and composition with the type of halide occurred in the sequence, Cl < Br < I. For each composition, both conductivity and mobility increased with temperature. The mobile ion concentration was found to be about 10 23 m -3 at 293 K, and it was insensitive to the type of halide as well as temperature. The results suggest that the change in ionic conductivity with the temperature and the type of halide present is mainly attributable to the change in ionic mobility rather than carrier concentration. Moreover, the electronic conductivity was found to be about 10 -6 Ω -1 m -1 at 293 K. Thus, the electronic contribution to the total conductivity is negligibly small.

Effects of deposition condition on the ionic conductivity and structure of amorphous lithium phosphorus oxynitrate thin film

Thin film rechargeable lithium batteries, in forms of Li{vert_bar}Li{sup +} solid electrolyte{vert_bar}Li intercalation cathode, have been studied for their applications in electronic devices such as built-in power sources for RAM, CMOS chips and smart cards. Recently, it was reported that a new amorphous lithium electrolyte, lithium phosphorus oxynitride (LIPON), showed an ionic conductivity as high as 2.0 x 10{sup {minus}6} {Omega}{sup {minus}1} cm{sup {minus}1} at room temperature, and also excellent long term stability when in contact with lithium. In spite of the advantages of LIPON as a solid electrolyte for microbatteries, the influence of deposition parameters on the structure and ionic conductivity on the LIPON is not yet known. the objective of the present study is to examine the effect of deposition conditions on the ionic conductivity and structural change of the LIPON solid electrolyte films, and hence to elucidate the mechanism by which the incorporation of nitrogen into phosphate glass improves the Li{sup +} ionic conductivity of LIPON.

Ionic conductance determinants of synaptic memory nets and their implications for Alzheimer's disease

Electrical and chemical signals representing macroscopic "perturbations" in brain networks engage large numbers of transient "microscopic" ionic channel fluctuations in producing long-lasting changes of conductance (and thus potential). Repeated electrical and chemical signals that occur during associative training of living organisms (from mollusc to mammal) can cause ionic conductance changes lasting from days to many weeks. If a stimulus pattern reoccurs with sufficient frequency, voltage-dependent K(+) conductances-responsible for both synaptic and intrinsic membrane currents-become progressively less probabilistic and more deterministic. In effect, more deterministic ion channel functions record in associative memory more deterministic (i.e., higher probability) events in the environment. This memory has been found to be stored within brain networks as ensembles of local dendritic ionic conductance changes distributed throughout brain regions such as the hippocampus and cerebellar cortex. Numerous other studies taken together support the hypothesis that distributed dendritic loci store associative memory, do not involve long-term potentiation, are also loci for Alzheimer's disease (AD) pathophysiology, and can contribute to, if not be responsible for, early memory loss in clinically manifest AD. J. Neurosci. Res. 58:24-32, 1999. Published 1999 Wiley-Liss, Inc.

Determining PCB Sorption/Desorption Behavior on Sediments Using Selective Supercritical Fluid Extraction. 3. Sorption from Water

Supercritical fluid extraction (SFE) with pure CO2 was used to quantitatively remove PCBs from historically contaminated sediments without substantially disturbing their bulk organic or inorganic matrix as evidenced by only small or undetectable changes in thermal gravimetric behavior, elemental (C, H, N, S) composition, ionic conductivity, and pH determined before and after SFE. The extracted PCBs were then spiked into water with the parent sediment, and sorption was allowed to occur for up to 18 days. The selective SFE conditions developed in part 1 were used to determine the proportion of PCBs which could be extracted under four conditions of increasing stringency. Comparing the selective SFE behavior of the PCBs from the water/sediment sorption samples to the original historically contaminated sediments demonstrated that 18 days was not sufficient for PCBs to migrate to the “slower” sediment-binding sites (those sites requiring more rigorous SFE conditions), which the PCBs had occupied in the historically contaminated sediments and that the adsorbed PCBs were primarly associated with the binding sites most easily extracted (“rapidly desorbed”) by SFE. Sediment/water distribution coefficients at 18 days were similar for sediments with low contamination levels (<50 ng/g of individual congeners) and high contamination levels (∼300−4000 ng/g). Apparent distribution coefficients (Kds) at 18 days were similar (within a factor of 2) for the various sediments regardless of congener molecular weight or concentration. Kds increased by a factor of ∼4−8 when exposure was increased from 2 h to 18 days, with the most rapidly sorbed molecules corresponding to those molecules most rapidly desorbed by selective SFE.

Order–disorder of the A-site ions and lithium ion conductivity in the perovskite solid solution La0.67−xLi3xTiO3 (x=0.11)

The A-site-deficient perovskite solid solution (ADPESS) La0.67−xLi3xTiO3 (x=0.11) underwent an order–disorder transition reversibly with a reversible change in ionic conductivity. The cubic, disordered form (a=ap) was obtained by quenching from temperatures above ∼1150°C, while the tetragonal, ordered form (a=ap, c≈2ap), by annealing at temperatures below ∼1150°C. Since controlled thermodynamically, the extent of ordering of La ions could be changed reversibly by annealing in a range of 600–1150°C. The equilibrated order parameter S increased continuously from 0 at 1150°C to ∼0.83 at 600°C with decreasing annealing temperature. The bulk ionic conductivity at 25°C had a small maximum at S≈0.2 and decreased increasingly rapidly with increasing extent of ordering in a range of S>0.2. The tetragonal distortion of the subcell began at S≈0.2. The distortion became more manifest and the lattice parameters a contracted more with increasing extent of ordering in a range of S>0.2. The decrease in ionic conductivity is attributed to an increase in activation energy for ionic conduction, which is presumably associated with the contraction of the lattice parameter a of the subcell.

Effect of alumina additions upon electrical properties of 8 mol.% yttria-stabilised zirconia

Solid oxide fuel cells (SOFCs) are energy converters that directly transform the chemical energy of combustible gases into electrochemical energy by oxidation. The design of SOFC, which has the highest volumetric power density, is a planar one in which the electrolyte, yttria-stabilised zirconia (YSZ), can be optimised by strengthening with small additions of α-Al2O3. Different commercial powders have different impurity contents and thus show different changes in ionic conductivity when α-Al2O3 is added. We describe the changes in oxide ion conductivity of Tosoh 8 mol.% YSZ that has been added to with α-alumina. AC impedance measurements show that small additions (∼1 wt.%) of Al2O3 can cause the ionic conductivity of Tosoh 8YSZ to increase due to a decrease in the grain boundary impedance which is observable at low to medium temperatures. Small wt.% additions of α-Al2O3 also cause an overall decrease in the high temperature impedance of 8YSZ. We have found that 10 wt.% alumina can be added to 8YSZ without any significant decrease in ionic conducting properties. Further additions of alumina cause a rapid decrease in conductivity due to the large volume percent of insulating alumina phases, which are present, and also due to the cracking of pellets that occurs on firing. We also report the improved stability of added-alumina 8YSZ to hydrothermal ageing. Hydrothermal ageing of unadded to 8YSZ, in an autoclave at 180°C, can lead to a decrease in the conductivity at 1000°C by as much as 40%. The drop in conductivity of 8YSZ can be limited to a decrease of only 10% by the addition of greater than 5 wt.% Al2O3.

Lysophosphatidic Acid Stimulates Neurotransmitter-Like Conductance Changes that Precede GABA and l-Glutamate in Early, Presumptive Cortical Neuroblasts

During neurogenesis in the embryonic cerebral cortex, the classical neurotransmitters GABA and L-glutamate stimulate ionic conductance changes in ventricular zone (VZ) neuroblasts. Lysophosphatidic acid (LPA) is a bioactive phospholipid producing myriad effects on cells including alterations in membrane conductances (for review, see Moolenaar et al., 1995). Developmental expression patterns of its first cloned receptor gene, lpA1/vzg-1 (Hecht et al., 1996; Fukushima et al., 1998) in the VZ suggested that functional LPA receptors were synthesized at these early times, and thus, LPA could be an earlier stimulus to VZ cells than the neurotransmitters GABA and L-glutamate. To address this possibility, primary cultures of electrically coupled, presumptive cortical neuroblast clusters were identified by age, morphology, electrophysiological profile, BrdU incorporation, and nestin immunostaining. Single cells from cortical neuroblast cell lines were also examined. Whole-cell variation of the patch-clamp technique was used to record from nestin-immunoreactive cells after stimulation by local administration of ligands. After initial plating at embryonic day 11 (E11), cells responded only to LPA but not to GABA or L-glutamate. Continued growth in culture for up to 12 hr produced more LPA-responsive cells, but also a growing population of GABA- or L-glutamate-responsive cells. Cultures from E12 embryos showed LPA as well as GABA and L-glutamate responses, with LPA-responsive cells still representing a majority. Overall, >50% of cells responded to LPA with depolarization mediated by either chloride or nonselective cation conductances. These data implicate LPA as the earliest reported extracellular stimulus of ionic conductance changes for cortical neuroblasts and provide evidence for LPA as a novel, physiological component in CNS development.

Ion conductances related to development of repetitive firing in mouse retinal ganglion neurons in situ

In the retina, the ability to encode graded depolarizations into spike trains of variable frequency appears to be a specific property of retinal ganglion neurons (RGNs). To deduce the developmental changes in ion conductances underlying the transition from single to repetitive firing, patch-clamp recordings were performed in the isolated mouse retina between embryonic day 15 (E15) and postnatal day 5 (P5). Immature neurons of the E15 retina were selected according to their capacity to generate voltage-activated Na+ currents (INa(V)). Identification of P5 RGNs was based on retrograde labeling, visualization of the axon, or the amplitude of INa(V). At E15, half of the cells were excitable but none of them generated more than one spike. At P5, all cells were excitable and a majority discharged in tonic fashion. Ion conductances subserving maintenance of repetitive discharge were identified at P5 by exposure to low extracellular Ca2+, Cd2+, and charybdotoxin, all of which suppressed repetitive discharge. ω-Conotoxin GVIA and nifedipine had no effect. We compared passive membrane properties and a variety of voltage-activated ion channels at E15 and P5. It was found that the density of high voltage-activated (HVA) Ca2+ currents increased in parallel with the development of repetitive firing, while the density of Ni2+-sensitive low voltage-activated (LVA) Ca2+ currents decreased. Changes in density and activation kinetics of tetrodotoxin-sensitive Na+ currents paralleled changes in firing thresholds and size of action potentials, but seemed to be unrelated to maintenance of repetitive firing. Densities of A-type K+ currents and delayed rectifier currents did not change. The results suggest that HVA Ca2+ channels, and among them a toxin-resistant subtype, are specifically engaged in activation of Ca2+-sensitive K+ conductance and thereby account for frequency coding in postnatal RGNs. © 1999 John Wiley & Sons, Inc. J Neurobiol 38: 191–206, 1999

Ion conductances related to development of repetitive firing in mouse retinal ganglion neuronsin situ

In the retina, the ability to encode graded depolarizations into spike trains of variable frequency appears to be a specific property of retinal ganglion neurons (RGNs). To deduce the developmental changes in ion conductances underlying the transition from single to repetitive firing, patch-clamp recordings were performed in the isolated mouse retina between embryonic day 15 (E15) and postnatal day 5 (P5). Immature neurons of the E15 retina were selected according to their capacity to generate voltage-activated Na+ currents (I(Na)(v)). Identification of P5 RGNs was based on retrograde labeling, visualization of the axon, or the amplitude of I(Na)(v). At E15, half of the cells were excitable but none of them generated more than one spike. At P5, all cells were excitable and a majority discharged in tonic fashion. Ion conductances subserving maintenance of repetitive discharge were identified at P5 by exposure to low extracellular Ca2+, Cd2+, and charybdotoxin, all of which suppressed repetitive discharge. omega-Conotoxin GVIA and nifedipine had no effect. We compared passive membrane properties and a variety of voltage-activated ion channels at E15 and P5. It was found that the density of high voltage-activated (HVA) Ca2+ currents increased in parallel with the development of repetitive firing, while the density of Ni2+-sensitive low voltage-activated (LVA) Ca2+ currents decreased. Changes in density and activation kinetics of tetrodotoxin-sensitive Na+ currents paralleled changes in firing thresholds and size of action potentials, but seemed to be unrelated to maintenance of repetitive firing. Densities of A-type K+ currents and delayed rectifier currents did not change. The results suggest that HVA Ca2+ channels, and among them a toxin-resistant subtype, are specifically engaged in activation of Ca2+-sensitive K+ conductance and thereby account for frequency coding in postnatal RGNs.

Kinetics of the competitive response of receptors immobilised to ion-channels which have been incorporated into a tethered bilayer.

A competitive ion channel switch (ICS) biosensor has been modelled yielding ligand mediated monomer-dimer reaction kinetics of gramicidin (gA) ion-channels within a tethered bilayer lipid membrane. Through employing gramicidin A, functionalized with the water-soluble hapten digoxigenin, it is possible to cross-link gramicidin to antibody fragments tethered at the membrane/aqueous interface. The change in ionic conductivity of the channel dimers may then be used to measure the binding kinetics of hapten-protein interactions at the membrane surface. The approach involves measuring the time dependence of the increase in impedance following the addition of a biotinylated antibody fragment (b-Fab'), which cross-links the functionalized gramicidin monomers in the outer layer of the lipid bilayer to tethered membrane spanning lipid. The subsequent addition of the small molecule digoxin, (M(r) 781 Da), competes with and reverses this interaction. The model provides a quantitative description of the response to both the cross-linking following the addition of the b-Fab' and the competitive displacement of the hapten by a water-soluble small analyte. Good agreement is obtained with independent measures of the cross-linking reaction rates of the gramicidin monomer-dimer and the b-Fab: hapten complex. The rate and amplitude of the competitive response is dependent on concentration and provides a fast and sensitive detection technique. Estimates are made of the concentration of gramicidin monomers in both the inner and outer monolayer leaflets of the membrane. This is used in the calculation of the gramicidin monomer/dimer equilibrium constant, K2D3. Other considerations include the membrane impedance limit set by the membrane leakage which is also a function of the concentration of the gA monomer concentration, and the two-dimensional kinetic association constant k2D2, of the hapten: b-Fab' complex. The gA dimer concentration is dependent on both the concentration of gA-dig and of the tethered streptavidin: b-Fab' complexes. The model shows that the 2D dissociation constant k2D3(-1), must be at least 10 times faster than the 3D dissociation constant k3D2(-1) for digoxin to completely reverse the cross-linked hapten-receptor interaction at the membrane interface.

In Vitro Studies of the Ultrastructural Changes Induced by Guanidine in the Nerves, Muscle Fibers and Neuromuscular Junction of the Mouse Diaphragm

1. The incubation of mouse isolated diaphragm with guanidine for 60 min produced ultrastructural changes in the neuromuscular junction, the intramuscular fascicles of the phrenic nerve and the skeletal muscle fibers. 2. The main morphological characteristics of both the end terminals and the nerve fibers were a swollen appearance and an electron-lucent axoplasm. In addition, the mitochondria in these regions were markedly swollen and showed a rarefaction of their cristae as well as a “washed aspect” of their matrix. Occasional periaxonal vacuoles were present in the myelinated axons. There was a reduction in the number of synaptic vesicles, which was accentuated by the enlarged areas of the majority of the terminals. 3. Muscle cells underwent a range of morphological alterations in the myofibrils and mitochondria. The most drastic type of necrosis affecting these cells was complete dissolution of the myofibrils, which resulted in an apparently “empty” cell with only the sarcolemma and a few mitochondria remaining intact. 4. Tetrodotoxin was unable to provide total protection against these guanidine-induced changes. 5. We conclude that the ultrastructural effects evoked by guanidine may be associated with modifications in the permeability of the axolemmal and sarcolemmal membranes as a result of changes in ionic conductance. Such ionic disturbances also interfere with the metabolism of mitochondria and the sarcoplasmic reticulum and may account for the well-known inhibitory effect of guanidine on K + channels and consequently on Ca 2+ and Na + conductances. 6. It is also suggested that the guanidine-induced alterations in the presynaptic and postsynaptic sites could have independent mechanisms of action.

Ammonia-induced depolarization of cultured rat cortical astrocytes

Exposure of cultured rat cortical astrocytes to increased concentrations of ammonia has been shown to induce morphological and biochemical changes similar to those found in hyperammonemic (e.g., hepatic) encephalopathy in vivo. Alterations of electrophysiological properties are not well investigated. In this study, we examined the effect of ammonia on the astrocyte membrane potential by means of perforated patch recordings. Exposure to millimolar concentrations of NH 4Cl induced a slow dose-dependent and reversible depolarization. At steady state, i.e., after several tens of minutes, the cells were significantly depolarized from a resting membrane potential of −96.2±0.6 mV ( n=83, S.E.M.) to −89.1±1.6 mV ( n=7, S.E.M.) at 5 mM NH 4Cl, −66.3±3.6 mV ( n=9, S.E.M.) at 10 mM NH 4Cl and −50.4±2.5 mV ( n=12, S.E.M.) at 20 mM NH 4Cl, respectively. In order to examine the underlying depolarizing mechanisms we determined changes in the fractional ion conductances for potassium, chloride and sodium induced by 20 mM NH 4Cl. No significant changes were found in the fractional sodium or chloride conductances, but the dominating fractional potassium conductance decreased slightly from a calculated 0.86±0.04 to 0.77±0.04 ( n=9, S.E.M.). Correspondingly, we found a significant fractional ammonium ion (NH 4 +) conductance of 0.23±0.02 ( n=10, S.E.M.) which was blocked by the potassium channel blocker barium and, hence, most likely mediated by barium-sensitive potassium channels. Our data suggest that the sustained depolarization induced by NH 4Cl depended on changes in intracellular ion concentrations rather than changes in ion conductances. Driven by the high membrane potential NH 4 + accumulated intracellularly via a barium-sensitive potassium conductance. The concomitant decrease in the intracellular potassium concentration was primarily responsible for the observed slow depolarization.

Photoinduced switching of ionic conductivity by metal ion complexes of vinyl copolymers carrying crowned azobenzene and biphenyl moieties at the side chain

Vinyl copolymers carrying crowned azobenzene and biphenyl moieties at the side chain were synthesized and their photoresponsive ion-conducting behavior was investigated in the presence of sodium perchlorate. Any of the copolymers or the homopolymer of crowned azobenzene can undergo photochemical switching of ionic conductivity in composite films containing an ion-conducting carrier. UV-light-induced isomerization of the azobenzene moiety causes some disorder in the crown ether moiety (an ion-hopping site), in the liquid crystal state of the polymers, thus decreasing ionic conductivity, and this is reversed by subsequent visible-light irradiation. The highest magnitude in the photoinduced ionic-conductivity changes was attained in polymers containing the highest content of crowned azobenzene moiety, owing to the more efficient photoinduced phase transition. The polymers with the highest content of crowned azobenzene moiety also showed the fastest response in photoinduced switching.

Photorefractivity Based on Photoinduced Ionic-conductivity Changes with Crowned Spirobenzopyran

Abstract Significant light diffraction by photorefractive effect has been realized with composite films consisting of a nonlinear optical compound, crowned spirobenzopyran, a polymeric lithium salt, and poly(methyl methacrylate), based on a mechanism of photochemical ionic-conduction control by the photochromic crown ether.

Ion transport in glassy electrolytes

Experimental and theoretical advances involving electrochemistry and ion transport in glass are briefly and selectively reviewed. Particular attention is paid to the problems of incorporating glasses in solid state batteries, and to the way changes in ionic conductivity can either be predicted or modelled theoretically. It is suggested that recent developments in theory, which relate ion mobility to glass structure, could lead to the discovery of new phenomena and to future practical developments in “glassy ionics”.

The kinetics of the crystallization of barium chromate in presence of polyphosphate and phosphonates

The inhibiting effect of polyphosphate and phosphonates on the crystallization of barium chromate for both seeded and unseeded systems has been investigated using the changes in ionic conductivity of the lattice ions in supersaturated solutions containing stoichiometric concentrations of barium and chromate at 298 K. The inhibitors studied are sodium tripolyphosphate (STP), ethylenediaminetetramethylenephosphonic acid (ENTMP), and 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP). The effect of these inhibitors on the growth of crystals has been studied at several inhibitor concentrations. The influence of these additives on barium chromate crystallization could be interpreted in terms of aLangmuir type adsorption isotherm. The crystallization retarding effect due to inhibitors is in the orderHEDP>STP>ENTMP. The inhibitors studied can be used as effective compounds for scale formation control.

Properties of a slow nonselective cation conductance modulated by neurotensin and other neurotransmitters in midbrain dopaminergic neurons.

1. A widespread mechanism of slow excitation throughout the nervous system involves overlapping changes in nonselective ion conductance and K+ conductance. We used whole cell patch-clamp recording to characterize such a nonselective conductance induced by neurotensin (NT) and other neurotransmitters in immunocytochemically identified dopaminergic neurons cultured from the rat ventral tegmental area (VTA). 2. The NT-induced inward current consisted of an initial peak and later "hump." The response was blocked reversibly by the nonpeptide NT-receptor antagonist SR48692, suggesting that it resulted from activation of NT receptors. 3. The channel was almost equally permeable to Na+ and K+, as determined from the reversal potential shift upon switching from Na+- to K(+)-containing external solution. The permeability of Cs+ was similar to that of Na+, as determined from the zero-current equation and average reversal potential in the 75 mM Na+ solution. Cl- was not significantly permeable. 4. In Ca(2+)-free external solution, the NT-induced current showed a fourfold increase in amplitude, and in high Mg2+ (20 mM) external solution, the NT-induced current showed an 80% decrease in amplitude, suggesting that external Ca2+ and Mg2+ could block the nonselective conductance. 5. The NT response was unaffected by loading the neurons with either the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid or with 1 mM ca2+. The nonselective conductance was therefore not Ca2+ activated. 6. Loading the neurons with cyclic GMP or cyclic AMP (each with the phosphodiesterase inhibitor isobutyl-methylxanthine) did not affect the NT response. The NT-induced nonselective conductance was therefore not cyclic nucleotide-activated. 7. The latency of the NT response was long (> or = 185 ms, average 406 ms, 30 degrees C), indicating that NT did not induce the conductance through ligand-gated channels. Thus, NT activated a slow nonselective cation conductance. 8. Neurokinin B, a metabotropic glutamate agonist, and muscarine elicited responses similar to the NT response. The NT response could be elicited after desensitizing the responses to these other neurotransmitters, indicating receptor specificity in the activation of the nonselective conductance.

Composite protonic solid electrolytes in the CsHSO 4-SiO 2 system

Transport, thermal and structural properties of the composite solid electrolytes (1 − x)CsHSO 4xSiO 2 (where x = 0–0.8) were investigated. The composites were prepared by mechanical mixing of components followed by heating at temperatures near CsHSO 4 melting point (483 K). The dependence of low temperature phase conductivity on x has a maximum with a value 2.5 orders of magnitude higher than that of pure CsHSO 4 and conductivity is governed by protons. Heterogeneous doping is shown to change markedly the thermodynamic parameters of the ionic component. The phase transition temperature CsHSO 4 in the composites decreases from 414 to 350 K with the increase of the content of heterogeneous additive SiO 2 from 0 to 0.7. As x raises CsHSO 4 the amorphization takes place and the relative change of ionic conductivity at phase transition diminishes, the phase transition becomes diffusive and disappears for the 0.2CsHSO 40.8SiO 2 composite.

Synthesis of Vinyl Polymers Incorporating Different Crowned Azobenzene Moieties and Their Application to Photoresponsive Ion-Conducting System

Abstract Vinyl polymers carrying a crowned azobenzene side chain, which have a crown ether moiety and an azobenzene moiety in two different ways, were synthesized and their ion-conducting behavior investigated. The crowned azobenzene vinyl polymer carrying a crown ether moiety apart from its azobenzene moiety, 1, exhibited distinct liquid crystal phases, which were stabilized by the addition of alkali metal perchlorates. Ion-conducting composite films containing crowned azobenzene vinyl polymer 1 underwent remarkable photoinduced ionic-conductivity switching. The system of vinyl polymer 2, which carries a crown-ether ring in the vicinity of its azobenzene moiety, is greater in the magnitude of photoinduced ionic-conductivity change (ionic-conductivity ratio) than the system of vinyl polymer 1. X-Ray diffraction measurements suggested that the difference in the ionic-conductivity switching between the two crowned azobenzene polymers is derived from the difference in the order–disorder arrangement of the crown ether moiety on the photoisomerization of the azobenzene moiety from its trans form to the corresponding cis one.