G.Z. Żukowska

A basic investigation of anhydrous proton conducting gel electrolytes

Abstract The aim of this paper is to summarize recent trends in the studies on nonaqueous proton conducting gel electrolytes. The physical–chemical properties of these systems are described and their relation to the type and concentration of polymer matrix, proton donor as well as the solvent used is discussed. This analysis is performed on the basis of electrochemical (impedance spectroscopy, cyclic voltammetry), spectroscopic (NMR, PFG NMR, FT-IR), and thermogravimetric (DSC) experiments. The proton conduction mechanism is postulated and its dependence on the sample composition is discussed. The possibility of application of proton conducting gels in electrochromic devices is presented.

Proton conducting polymer gel electrolytes

Abstract Novel proton conducting gel electrolytes from poly(vinylidene fluoride)-dimethylformamide-H 3 PO 4 system are synthesized and characterized by impedance spectroscopy, infra-red spectroscopy and differential scanning calorimetry. Highly conducting (5×10 −4 S/cm at 20°C) colorless polymeric membranes are obtained in a relatively narrow component concentration range. The gel electrolytes studied are thermally stable up to 70–120°C as shown by the DSC experiments.

Influence of the substituents on the structure and properties of benzoxaboroles.

Benzoxaboroles possessing aryl substituents in the oxaborole ring were synthesized, and their structures were determined by single-crystal X-ray diffraction. Structures in the solid state are centrosymmetric dimers with two intermolecular hydrogen bonds. These compounds were investigated using a combination of the spectroscopic and the computational approach, comparing their properties with the unsubstituted compound. Investigated compounds were characterized by (1)H, (13)C, and (11)B NMR spectroscopy in solution. Assignment of (1)H and (13)C signals was made on the basis of HSQC and HMBC spectra. The molecular structure of 1,3-dihydro-1-hydroxy-3-phenyl-2,1-benzoxaborole was calculated by the density functional (B3LYP) method with the extended 6-311++G(d,p) basis set. The calculated geometrical parameters were compared with experimental X-ray data, and the differences between experimental and calculated values were found to be of the order of experiment standard deviation, confirming a good description by this level of theory. The harmonic frequencies, potential energy distribution (PED), and IR intensities of this compound and its deuterated analogue were calculated with the B3LYP method. The assignment of the experimental spectra was made on the basis of the calculated PED. The consequence of dimer formation is the splitting of the vibrational modes into symmetric and antisymmetric vibrations. The structure modification resulting from the hydrogen bonded dimers formation is presented.

Nonaqueous gel electrolytes doped with phosphoric acid esters

Abstract Highly conducting anhydrous gels doped with phosphoric acid esters have been obtained by entrapping ester solutions in polar aprotic solvents into the poly(vinylidene fluoride) or poly(methyl methacrylate) matrices. The dependence of the physical–chemical properties of these materials on the type and concentration of proton donor, as well as solvent used, are described. It is found that use of propylene carbonate- N , N -dimethyl formamide solvent mixture allows to obtain transparent gels in a wide (5–40 mass%) ester concentration range. Conductivities exceeding 5×10 −4 S cm −1 (PVdF-based systems) and 1×10 −3 S cm −1 (PMMA-based gels) are reported. The mechanism of proton conduction is discussed on the basis of impedance spectroscopy and PFG NMR experiments.

Structural and spectroscopic properties of an aliphatic boronic acid studied by combination of experimental and theoretical methods

Boronic acids have emerged as one of the most useful class of organoboron molecules, with application in synthesis, catalysis, analytical chemistry, supramolecular chemistry, biology, and medicine. In this study, the structural and spectroscopic properties of n-butylboronic acid were investigated using experimental and theoretical approaches. X-ray crystallography method provided structural information on the studied compound in the solid state. Infrared and Raman spectroscopy served as tools for the data collection on vibrational modes of the analyzed system. Car-Parrinello molecular dynamics simulations in solid state were carried out at 100 and 293 K to investigate an environmental and temperature influence on molecular properties of the n-butylboronic acid. Analysis of interatomic distances of atoms involved in the intermolecular hydrogen bond was performed to study the proton motion in the crystal. Subsequently, Fourier transform of autocorrelation functions of atomic velocities and dipole moment was applied to study the vibrational properties of the compound. In addition, the inclusion of quantum nature of proton motion was performed for O-H stretching vibrational mode by application of the envelope method for intermolecular hydrogen-bonded system. The second part of the computational study consists of simulations performed in vacuo. Monomeric and dimeric forms of the n-butylboronic acid were investigated using density functional theory and Moller-Plesset second-order perturbation method. The basis set superposition error was estimated. Finally, atoms in molecules (AIM) theory was applied to study electron density topology and properties of the intermolecular hydrogen bond. Successful reproduction of the molecular properties of the n-butylboronic acid by computational methodologies, presented in the manuscript, indicates the way for future studies of large boron-containing organic systems of importance in biology or materials science.

Controlling the stereoselectivity of rac -LA polymerization by chiral recognition induced the formation of homochiral dimeric metal alkoxides

Using dimeric dialkylgallium and dialkylindium alkoxide catalysts for the polymerization of rac-lactide (rac-LA), we have shown for the first time that the formation of homochiral dimeric species [Me2MOR]2 (M = Ga, In), induced by chiral recognition of monomeric Me2MOR units in the presence of Lewis base, leads to an increase of the heteroselectivity of the ring opening polymerization (ROP) of rac-LA, and therefore provides a new tool for controlling the stereoselectivity of the polymerization of heterocyclic monomers. To explain the origin of the heteroselectivity of the [Me2Ga(μ-OCH(Me)CO2Me)]2/Lewis base system in the ROP of rac-LA, structure of (S,S)-[Me2Ga(μ-OCH(Me)CO2Me)]2 ((S,S)-1) and rac-[Me2Ga(μ-OCH(Me)CO2Me)]2 (1) in the absence and presence of tertiary amines and pyridines was investigated. Studies were further extended by analysis of the structure/activity data for both (S,S)-[Me2In(μ-OCH(Me)CO2Me)]2 ((S,S)-2) and rac-[Me2In(μ-OCH(Me)CO2Me)]2 (2). Contrary to gallium complex 1, which exists in a solution as equimolar mixture of homo- and heterochiral diastereomers, an excess of homochiral (R*,R*)-2 species was observed in the case of 2. For both the Ga and In complexes, the interaction of amines with the metal center increased the tendency for the formation of homochiral species with retention of the dimeric structure in the solution. This tendency was additionally demonstrated by the structure of model dialkylgallium (3) and indium (4) complexes with monoanionic ligands possessing chiral centers in the α-position to the alkoxide oxygen and pyridine functionalities. The polymerization of rac-LA with gallium and indium catalysts (S,S)-1 and (S,S)-2 resulted in the formation of heterotactically enriched polylactide (PLA) (Pr = 0.50–0.85) and (Pr = 0.54–0.72), respectively. The heteroselectivity of the investigated systems was in line with the excess of the homochiral catalytic species. The higher activity of homochiral species activated by amines resulted in a positive non-linear effect between an excess of homochiral (R*,R*)-1 or (R*,R*)-2 catalysts and the heterotacticity of the obtained PLA. The observed dependence of stereoselectivity of rac-LA polymerization on the excess of homochiral species was similar to the asymmetric amplification in enantioselective organic catalysis; however, it is exceptional in polymerization processes.

Characterization of perdeuterated H3PO4-doped nonaqueous gel electrolytes using 31P nuclear magnetic resonance spectroscopy

Abstract Proton conducting gel electrolytes based on a network of various polymer matrices such as methyl methacrylate (MMA) and glycidyl methacrylate (GMA) containing perdeuterated H 3 PO 4 have been synthesized using propylene carbonate (PC), dimethylformamide (DMF) and dimethylacetamide (DMA) as entrapped solvents. These systems have ionic conductivities as high as 10 −4 S cm −1 at ambient temperatures. The operating range of these electrolytes is from 220 to 370 K. In an attempt to understand their structure and dynamic properties, we report 31 P ( I =1/2) spectroscopic and self-diffusion coefficient ( D ) measurements of mobile phosphorus species for these materials at room temperature, using pulsed field-gradient Hahn spin-echo techniques. The 31 P NMR signal in some systems was found to have multiple peaks indicating the presence of o -phosphoric acid, charged dissociated species, and condensed phosphates. It is estimated that condensed phosphates comprise up to 40% of the phosphate species in GMA based electrolytes. As expected 31 P diffusion coefficients of the different phosphate species present are determined to be dependent on the size of the moving phosphate species.

Fluorine-free electrolytes for all-solid sodium-ion batteries based on percyano-substituted organic salts

A new family of fluorine-free solid-polymer electrolytes, for use in sodium-ion battery applications, is presented. Three novel sodium salts withdiffuse negative charges: sodium pentacyanopropenide (NaPCPI), sodium 2,3,4,5-tetracyanopirolate (NaTCP) and sodium 2,4,5-tricyanoimidazolate (NaTIM) were designed andtested in a poly(ethylene oxide) (PEO) matrix as polymer electrolytes for anall-solid sodium-ion battery. Due to unique, non-covalent structural configurations of anions, improved ionic conductivities were observed. As an example, “liquid-like” high conductivities (>1 mS cm−1) were obtained above 70 °C for solid-polymer electrolyte with a PEO to NaTCP molar ratio of 16:1. All presented salts showed high thermal stability and suitable windows of electrochemical stability between 3 and 5 V. These new anions open a new class of compounds with non-covalent structure for electrolytes system applications.

Ambient and subambient temperature proton-conducting polymer gel electrolytes

Abstract Nonaqueous proton-conducting polymer gels have been synthesized and characterized by impedance spectroscopy and cyclic voltammetry. Special emphasis has been put to the subambient temperature characteristics of the samples studied with respect to their possible application in electrochromic devices. The gels studied exhibit ambient temperature conductivities exceeding 10 −3 S/cm, which remains higher than 10 −4 S/cm even at −50 °C. The electrochemical stability of the studied protonic gels depends mainly on the type of solvent used and is the highest for samples plasticized with propylene carbonate.

Ternary mixtures of ionic liquids for better salt solubility, conductivity and cation transference number improvement

We hereby present the new class of ionic liquid systems in which lithium salt is introduced into the solution as a lithium cation−glyme solvate. This modification leads to the reorganisation of solution structure, which entails release of free mobile lithium cation solvate and hence leads to the significant enhancement of ionic conductivity and lithium cation transference numbers. This new approach in composing electrolytes also enables even three-fold increase of salt concentration in ionic liquids.