Concomitant reactivity of the m-Terphenylindium dihydroxide [2,6-Mes2C6H3In(OH)2]4 toward carbon dioxide and ethylene glycol

The stepwise reaction of [2,6-Mes₂C₆H₃In(OH)₂]₄ with carbon dioxide and ethylene glycol proceeded with the formation of (2,6-Mes₂C₆H₃In)₄(CO₃)₂(OH)₄(H₂O)₂ (1) and (2,6-Mes₂C₆H₃In)₄(OCH₂CH₂O)₂(OH)₄ (2), respectively, and eventually produced (2,6-Mes₂C₆H₃In)₄(CO₃)₂(OCH₂CH₂OH)₂(OH)₂ (3). Attempts to liberate ethylene carbonate upon heating of 3 were unsuccessful.

Enhancement of ion dynamics in PMMA-based gels with addition of TiO2 nano-particles

Solvent and ion dynamics in PMMA based gels have been investigated as a function of the loading of nanosized TiO₂ particles. The gels have a molar ratio of 46.5:19:4.5:30 of ethylene carbonate (EC), propylene carbonate (PC), lithium perchlorate and PMMA, respectively. A series of samples with 0, 4, 6 and 8 wt.% TiO₂ filler were investigated. The diffusion coefficients for the lithium ions and for the two solvents (EC and PC) were investigated by pfg-NMR. It was shown that the addition of filler to the gel electrolytes enhances the diffusion of the cations, while the diffusion of the solvents remains constant. Raman measurements show no significant changes in ion–ion interactions with the addition of fillers, while the ionic conductivity is seen to decrease. However, the sample with 8 wt.% TiO₂ had a conductivity close to that of the unfilled sample.

7Li NMR measurements of polymer gel electrolytes

Ion conducting polymer gels prepared from (ethylene oxide)_n grafted methacrylates, ethylene carbonate (EC), gamma butyrolactone (gBL), and lithium hexafluorophosphate are studied by means of nuclear magnetic resonance spectroscopy. This study shows that there are at least two possible lithium sites with different mobility. The lithium-ions with lower mobility dominate at room temperature, but this is changed as the temperature is increased. The NMR results also show that the ⁷Li spin–spin relaxation time decreases with increasing length of the grafted ethylene oxide side chains, indicating a stronger interaction between the polymer and the Li-ions, and hence, a lower mobility of the Li-ions.

Transport properties of ionic liquid electrolytes with organic diluents

Ionic liquids (ILs) form a novel class of electrolytes with unique properties that make them attractive candidates for electrochemical devices. In the present study a range of electrolytes were prepared based on the IL N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl) amide ([C₃mpyr][NTf₂]) and LiNTf2 salt. The traditional organic solvent diluents vinylene carbonate (VC), ethylene carbonate (EC), tetrahydrofuran (THF) and toluene were used as additives at two concentrations, 10 and 20 mol%, leading to a ratio of about 0.6 and 1.3 diluent molecules to lithium ions, respectively. Most promisingly, the lithium ions see the greatest effect in the presence of all the diluents, except toluene, producing a lithium self-diffusion coefficient of almost a factor of 2.5 times greater for THF at 20 mol%. Raman spectroscopy subtly indicates that THF may be effectively breaking up a small portion of the lithium ion–anion interaction. While comparing the measured molar conductivity to that calculated from the self-diffusion coefficients of the constituents indicates that the diluents cause an increase in the overall ion clustering. This study importantly highlights that selective ion transport enhancement is achievable in these materials.

Compositional effects on structure and transport properties in a polyelectrolyte gel

The copolymerization of lithium 2-acrylamido-2-methyl-1-propane sulfonate (LiAMPS) with N,N ′-dimethylacrylamide has yielded polyelectrolyte systems which can be gelled with an ethylene carbonate/N ′,N ′-dimethylacetamide solvent mixture and show high ionic conductivities. 7Li linewidth and relaxation times as well as 1H NMR diffusion coefficients have been used to investigate the effect of copolymer composition as well as copolymer concentration in the gel electrolyte with respect to ionic transport and polyelectrolyte structure. It appears that ion association is likely even in the case of low lithium salt concentration; however a rapid exchange exists between the associated and non-associated lithium species. Beyond 0.2 M of LiAMPS, both the conductivity and solvent diffusion reach a plateau, whilst lithium ion linewidth and spin-spin relaxation are suggestive, on average, of a less mobile species. The thermal analysis data is also supportive of this association effectively leading to a form of phase separation on the nanoscale, which gives a lower overall activity of lithium ions in the solvent rich regions beyond about 0.2 M of LiAMPS, thereby leading to an increase in the final liquidus temperature of the binary liquid solvent from –9 to +5°C.

Enhancement of ion dissociation in polyelectrolyte gels

High conductivity in single ion conducting polymer electrolytes is still the ultimate aim for many electrochemical devices such as secondary lithium batteries. Achieving effective ion dissociation in these cases remains a challenge since the active ion tends to remain in close proximity to the backbone charge as a result of a low degree of ion dissociation. A unique aspect of this dissociation problem in polyelectrolytes is the repulsion between the backbone charges created by dissociation. One way of enhancing ion dissociation in polyelectrolyte systems is to use copolymers in which only a fraction (<20%) of the mer units are charged and where the comonomer is itself chosen to be polar and preferably to be compatible with potential solvents. We have also found that certain dissociation enhancers based on ionic liquids or boroxine ring compounds can lead to high ionic conductivity. In the cases where an ionic liquid is used as the solvent in a polyelectrolyte gel, the viscosity of the ionic liquid and its hydrophilicity are critical to achieving high conductivity. Compounds based on the dicyanamide anion appear to be very effective ionic solvents; polyelectrolyte gels incorporating such ionic liquids exhibit conductivities as high as 10⁻² S/cm at room temperature. In the case of boroxine ring dissociation enhancers, gels based on poly(lithium-2-acrylamido-2-methyl-1-propanesulfonate) and ethylene carbonate produce conductivities approaching 10⁻³ S/cm. This paper will discuss these approaches for achieving higher conductivity in polyelectrolyte materials and suggest future directions to ensure single ion transport.

Gel electrolytes based on lithium modified silica nano-particles

In this work lithium modified silica (Li-SiO₂) nano-particles were synthesized and used as a single ion lithium conductor source in gel electrolytes. It was found that Li-SiO₂ exhibited good compatibility with DMSO, DMA/EC (a mixture of N,N-dimethyl acetamide and ethylene carbonate) and the ionic liquid, N-methyl-N-propyl pyrrolidinium bis(trifluoromethylsulfonyl) amide ([C₃mpyr][NTf₂]). Several gel electrolytes based on Li-SiO₂ were obtained. These gel electrolytes were investigated by DSC, solid state NMR, conductivity measurements and cyclic voltammetry. Conductivities as high as 10⁻³ S/cm at room temperature were observed in these nano-particle gel electrolytes. The results of electrochemical tests showed that some of these materials were promising for using as lithium conductive electrolytes in electrochemical devices, with high lithium cycling efficiency evident.

Boroxine ring compounds as dissociation enhancers in gel polyelectrolytes

In order to combine the advantages of both traditional gel electrolytes and polyelectrolytes, a novel polyelectrolyte which incorporates a boroxine ring-containing anion-trapping agent has been explored. Poly(lithium 2-acrylamido-2-methyl-1-propanesulfonate) (PAMPSLi), ethylene carbonate (EC) and tri(methoxyethoxyethoxyethoxy)boroxine (TME₃Bx) were combined to prepare various gel systems. The thermal properties and conductivities of these gels have been investigated. A conductivity of 10^−3.6 S cm⁻¹ at 20 °C has been achieved in a gel polyelectrolyte system with a molar ratio of [EC]:[TME3Bx]:[Li⁺]=24:1.7:1. Temperature-dependent NMR measurements indicated that a significant interaction exists between the boroxine ring and the polyelectrolyte.

The electrochemistry of lithium in ionic liquid/organic diluent mixtures

The electrochemistry of lithium is investigated in a number of electrolytes that consist of a lithium salt dissolved in a combined ionic liquid-organic diluent medium. We find that ethylene carbonate and vinylene carbonate improve electrochemical behaviour, while toluene and tetrahydrofuran are less promising.We also present insights into the electrode passivation caused by these diluents in an ionic liquid electrolyte during lithium cycling. We observe that during lithium cycling those electrolytes with carbonate based diluents are the most able to utilise their previously reported improved lithium ion diffusivities. Conversely, tetrahydrofuran, the most promising diluent of those studied in terms of its known ability to increase lithium ion diffusivity is found not to be as advantageous as a diluent. It appears that the poor electrochemical interfacial properties of the tetrahydrofuran electrolyte prevented the realisation of the benefits of the high solution lithium ion diffusivity.

Effect of flame-retarding additives on surface chemistry in Li-ion batteries

This study examined the properties of 1 wt.% vinylene carbonate, vinyl ethylene carbonate, and diphenyloctyl phosphate additive electrolytes as a promising way of beneficially improving the surface and cell resistance of Li-ion batteries. The additive electrolytes were dominant both in surface formation and internal resistance. In particular, electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy confirmed that diphenyloctyl phosphate is an excellent additive to the electrolyte in the Li-ion batteries due to the improved co-intercalation of the solvent molecules.

Nano-capsules of amphiphilic poly (ethylene glycol)-block-poly (bisphenol A carbonate) copolymers via thermodynamic entrapment

The synthesis of amphiphilic poly(ethylene glycol)-block-poly(bisphenol A carbonate) (PEG-b-PC) block copolymer is presented here using a simple bio-chemistry coupling reaction between poly(bisphenol A carbonate) (PC) with a monomethylether poly(ethylene glycol) (mPEG-OH) block, mediated by dicyclohexylcarbodiimide/4-dimethylaminopyridine. This method inherently allows great flexibility in the choice of starting materials as well as easy product purification only requiring phase separation and water washing. Collective data from Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and modulated dynamic scanning calorimetry (MDSC) confirmed the successful attachment of the poly(ethylene glycol) (mPEG-OH) and poly(bisphenol A carbonate) (PC) blocks. The preparation of nano-capsules was carried out by sudden addition of water to PEG-b-PC copolymers dispersed in THF, resulting in the controlled precipitation (i.e. thermodynamic entrapment) of the copolymer. Nano-capsules as small as 85 nm ± 30 nm were produced using this simple and fast methodology. We also demonstrate that encapsulating a water-insoluble bisphenol A diglycidyl ether (DGEBA) epoxy resin is possible highlighting the potential use of these capsules as a chemical delivery system.

Possible influence of Gondwanan glaciation on low-latitude carbonate sedimentation and trans-equatorial faunal migration: the lower Permian of South China

Peculiar Early Permian palaeontological and sedimentological features are reviewed from South China, including characteristic Early Permian cold-water Gondwanan brachiopod taxa and faunas from Sichuan and Guizhou provinces, widespread rosettes and irregular aggregates of calcite prisms ('Chrysanthemum Stones') within the Qixia limestones, and lack of significant Early Permian reef buildups. The occurrences of these features are at odds with the currently widely held view that South China was located in a palaeotropical, warm-water setting throughout the Permian and hence harboured a highly diverse shallow marine biota. In this paper, I propose a working hypothesis, suggesting that influence of at least cool water masses may have intermittently occurred in South China during the Early Permian, which facilitated the formation of the cool water-influenced palaeontological and sedimentological features and promoted the interchanges of cool to cold water marine faunas between the Gondwanan and Boreal Realms. These cool water masses may have been transported to low-latitude regions as deep currents from northern and eastern shelves of Gondwanaland and upwelled along the western coast of South China as well as within the relatively deep-water basins of central South China. Prevalence of these meridional, north-directed deep cold water currents during the Early Permian may have been related to the glaciation event of Gondwanaland. An alternative and/or additional source of cooling may have also originated from strong easterly palaeoequatorial boundary currents operating within the Palaeotethys at times during the Early Permian, inducing and/or enhancing upwelling of cool to cold water masses in the eastern Palaeotethys. This latter scenario is analogous to the occasional 'La Nina' effect (opposite to the 'El Nino' effect) at the equatorial belt of the modern Pacific Ocean.

Effect of synthesis parameters on the electrical conductivity of polypyrrole-coated poly(ethylene terephthalate) fabrics

The effects of pyrrole, anthraquinone-2-sulphonic acid (AQSA) and iron(III) chloride (FeCl3) concentrations, reaction time and temperature on the electrical conductivity of polypyrrole (PPy) - coated poly(ethylene terephthalate) (PET) fabrics were investigated. With an increase in both the AQSA and FeCl3 concentrations, resistivity decreased to a point beyond which higher concentrations led to increased surface resistivity. Erosion of the polymer coating, in dynamic synthesis from continual abrasion, manifested as an exponential increase in the resistance of the coated textile substrate. This was not encountered in static synthesis conditions. Temperature affected the degree of surface and bulk polymerisation. The effect of polymerisation temperature on conductivity was negligible. Conductive polymer coating on textiles through chemical polymerisation enabled a smooth coherent film to encase individual fibres, which did not affect the tactile properties of the host substrate. The optimum FeCl3/pyrrole and AQSA FeCl3/pyrrole molar ratios were found to be 2.22 and 0.40 respectively.

A dimeric tellurastannoxane carbonate cluster, tetra-tert-butyl-di-µ3-carbonato-tetrakis-[4-(N,N-dimethylamino)phenyl]di-µ-oxo-ditelluriumditin chloroform tetrasolvate

The title compound, [Sn₂Te₂(C₄H₉)₄(CO₃)₂O₂(C₈H₁₀N)₄]·4CHCl₃ or [(p-Me₂NC₆H₄)₂TeOSn^tBu₂CO₃]₂·4CHCl₃, contains an almost planar centrosymmetric inorganic Sn₂Te₂O₈C₂ core and hypercoordinated Sn and Te atoms. The structure features four secondary intramolecular Te...O contacts.

Phase behavior and crystallization in blends of a low molecular weight polyethylene-block-poly(ethylene oxide) diblock copolymer and poly(hydroxyether of bisphenol A)

The phase behavior, morphology and crystallization in blends of a low-molecular-weight (Mn = 1400) double-crystalline polyethylene-block-poly(ethylene oxide) (PE-PEO) diblock copolymer with poly(hydroxyether of bisphenol A) (PH) were investigated by differential scanning calorimetry, transmission electron microscopy and small-angle X-ray scattering. The symmetric PE-PEO diblock copolymer consists of a PH-miscible PEO block and a PH-immiscible PE block. However, PH only exhibits partial miscibility with the PEO block of the copolymer in the PH/PE-PEO blends; both macrophase and microphase separations took place. There existed two macrophases in the PH/PE-PEO blends, i.e., a PH-rich phase and a PE-PEO copolymer-rich phase. The PE block of the copolymer in the blends exhibited fractionated crystallization behavior by homogeneous nucleation. There appeared three crystallization exotherms related to the crystallization of the PE block within three different microenvironments in the PH/PE-PEO blends.