Mary Anne Mehta

The use of boroxine rings for the development of high performance polymer electrolytes

Abstract Boroxine ring containing additives, Bx( n )=B 3 O 3 [O(CH 2 CH 2 O) n CH 3 ] 3 , were found to be compatible with a wide variety of polymer hosts. Polymer electrolytes exhibiting room temperature conductivities of up to 10 −5 S cm −1 were obtained by incorporation of Bx( n ) and LiCF 3 SO 3 into poly(methyl methacrylate) and propylene oxide–ethylene oxide co-polymers. Polymers composed of inter-connecting networks of boroxine rings were also investigated as suitable hosts for the boroxine additives B 3 O 3 [O(CH 2 CH 2 O) n CH 3 ] 3 . Poly(methyl methacrylate) systems exhibited an electrochemical stability window in the region of 4.9 V, while transference number measurements indicated high Li + ion conductivity.

Boroxine ring containing polymer electrolytes

Abstract Anion trapping polymer electrolytes incorporating boroxine (B 3 O 3 ) rings and oligoether side chains have been demonstrated to combine high Li + ion transference numbers, thermal stability and an electrochemical stability window in the region of 4.9 V. Ionic conductivities of up to 1.6×10 −5 S cm −1 at 30°C and which exhibit Volger–Tamman–Fulcher (VTF) behaviour have been observed.

Molecular design of inorganic-organic hybrid polyelectrolytes to enhance lithium ion conductivity

Abstract Three types of inorganic–organic hybrid polymers containing the ate complex structure (e.g. aluminate, borate) were prepared as lithium ion conducting polymer electrolytes. The relationship between polymer structure and ionic conductivity was discussed from which it was shown that the concepts of molecular design used were very important. Ionic conductivity was enhanced by the introduction of Lewis acid groups, which reduced the charge density on the ate complex and weakened ion pairing between the lithium ion and the immobilized anion. Ionic conductivity was found to be dependent on the length and structure of the oligoether chain. In addition, introduction of bulky groups onto the polymer backbone in the region of the oligoether chain restricted the mobility of the latter.

Novel inorganic–organic polymer electrolytes – preparation and properties

Abstract Anion trapping polymer electrolytes were prepared from polymer hosts incorporating boroxine rings and pendant oligoether side chains. The materials exhibited high Li + transference numbers and high ionic conductivity. Evidence for anion interaction with the boroxine ring was obtained from solid 11 B-NMR spectroscopy.

Synthesis and characterization of aluminate polymer electrolytes and their blends with poly(ether)s

Abstract A series of single ion conducting aluminate polymer electrolytes were synthesized and their blends with poly(ether)s characterized. A great improvement of mechanical properties and processability was obtained upon blending with poly(ethylene oxide) or an ethylene oxide–propylene oxide copolymer. Enhancement of the ionic conductivity of blended polymer electrolytes was observed by adding LiCF 3 SO 3 and cationic transference numbers were determined to be about 0.56.

Application of the adsorption effect of optical fibres for the determination of critical micelle concentration

Abstract The critical micelle concentration (CMC) in surfactant solutions was detected by using an optical fiber. CMC detection is based on an adsorption effect in sample solutions consisting mainly of sodium dodecylbenzenesulfonate. An incident beam was reflected at the interface between the fiber core and the solution, passing through the sensing region along the fiber with repeating reflections. The change in adsorption condition leads to an effective change in refractive index at the surrounding surface of the core. The output signal suddenly increases at the CMC due to the reflectivity change caused by adsorption of surfactant molecules onto the surface of the fiber core. Two different types of fiber, plastic cladding silica fiber (PCS) with a silica glass core and a plastic optical fiber (POF) with a plastic core, were used for the experiments, where the cores were hydrophilic and hydrophobic, respectively. It was determined that the outputs from both PCS and POF fibers show a large change in output power at the CMC point as the surfactant concentration increases and also that adsorption onto the POF core occurs in a two-step process, that is some surfactant molecules have already started to adsorb onto the surface of the POF core even before CMC. CMC detection using an LED device is also proposed in the present paper.

Blended lithium ion conducting polymer electrolytes based on boroxine polymers

A new series of blended polymer electrolytes based on a boroxine polymer (BP) with poly(ethylene oxide) (PEO), an ethylene oxide–propylene oxide copolymer or poly(methyl methacrylate) were prepared. Good room temperature mechanical properties were exhibited by electrolytes containing in excess of 30% PEO. Cationic transference number measurements indicated that a slight improvement in lithium ion conductivity could be achieved by using a mixture of LiCF3SO3 and LiN(CF3SO2)2 as the electrolyte salt. Electrolytes incorporating significant proportions of BP exhibited reduced lithium–polymer electrolyte interfacial resistance.

Preparation and characterization of lithium ion conducting borosiloxane polymer electrolytes

Abstract A variety of lithium ion conducting borosiloxane polymers were prepared in high yield. The temperature dependence of ionic conductivity was fit well by the Vogel–Tammann–Fulcher equation, indicating that ion motion was strongly coupled to segmental motion of oligoether side chains. The borosiloxane electrolytes also exhibited large fractional free volume at the glass transition temperature, which led to enhanced ionic conductivity compared to electrolytes incorporating high molecular weight poly(ethylene oxide). The cationic transference number was enhanced due to anion interaction with the Lewis acidic sites on the polymer framework.

The Detection of Critical Micelle Concentration Based on the Adsorption Effect Using Optical Fibers

The structure of a surfactant molecule consists of two groups, a hydrophilic and a hydrophobic group. The possibility of detection of the critical micelle concentration (CMC) was examined using optical fibers, plastic cladding silica fiber (PCS) and plastic optical fiber (POF), with hydrophilic and hydrophobic core properties, respectively. The cladding was removed at the sensing region and the core was exposed to the sample solution. The output from both the PCS and POF increased drastically at the CMC of 3×10-3 mol/l. This was due to the rapid increase in the reflectance at the interface between the core and the sample solution as the surfactant molecules in the saturated solution began to adsorb onto the sensing region of the core surface.

Polymer electrolyte bilayer films with photorechargeable battery characteristics

Abstract Conversion of solar energy into chemical energy, storage and release upon discharge are photorechargeable battery characteristics. The preparation of polymer electrolyte bilayer films with photorechargeable battery characteristics formed by contact of two anionically conducting poly(ethylmethacryalate)/tributyl tin halide (Bu 3 SnX)/tetrabutyl ammonium halide (Bu 4 NX) films containing octylviologen and dibutylferrocene respectively are reported.