Anion Coordination Improves High-Temperature Performance and Stability of NaPF6-Based Electrolytes for Supercapacitors

Electrolyte stability can be improved by incorporating complexing agents that bind key decomposition intermediates and slow down decomposition. We show that hexamethyl-phosphoramide (HMPA) extends both the thermal stability threshold of sodium hexafluorophosphate (NaPF6) in dimethoxyethane (DME) electrolyte and the cycle life of double-layer capacitors. HMPA forms a stable complex with PF5, an intermediate in PF6 anion thermal degradation. Unbound, this intermediate leads to autocatalytic degradation of the electrolyte solution. The results of electrochemical impedance spectroscopy (EIS) and galvanostatic cycling measurements show large changes in the cell without the presence of HMPA at higher temperatures (≥60 °C). Fourier transform infrared spectroscopy (FTIR) on the liquid and gas phase of the electrolyte shows without HMPA the formation of measurable amounts of PF5 and HF. The complimentary results of these measurements proved the usefulness of using Lewis bases such as HMPA to inhibit the degradation of the electrolyte solution at elevated temperatures and potentially lead to improve cycle life of a nonaqueous capacitor. The results showed a large increase in capacitance retention during cycling (72% retention after 750,000 cycles). The results also provide evidence of major decomposition processes (0% capacitance retention after 100,000 cycles) that take place at higher temperatures without the additive of a thermal stability additive such as HMPA.

INFLUENCE OF THE SUBSTRATE ON THE CRYSTALLINE PHASE AND MORPHOLOGY OF POLY (VINYLIDENE FLUORIDE) (PVDF) THIN FILM

The effect of substrate on the crystalline phase and morphology of the poly (vinylidene fluoride) (PVDF) thin film has been investigated. The solution of PVDF/Hexamethyl phosphoramide (HMPA) was deposited on four different substrates, namely, silicon (Si), glass (SiO2), indium tin oxide (ITO) coated glass and silver (Ag) coated glass respectively by using the spin coating technique. The crystalline structure was investigated using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques. The morphology was determined using scanning electron microscopy (SEM). XRD demonstrated that the structure of PVDF thin films on each substrate is [Formula: see text]-phase with different orientations of the molecular chains. FTIR results confirmed XRD that the samples contain [Formula: see text]-phase. SEM shows spherulites structure, which is rough and porous, besides, the size of spherulites and the porosity are different for each sample. The size of spherulites is in average diameter range (1–6[Formula: see text][Formula: see text]m) and this range is attributed to the [Formula: see text]-phase. The nucleation process of [Formula: see text]-phase on the various substrates attributed either to the match of polymer-substrate or to the electrostatic interaction. Among the substrates used, the ITO substrate exhibited a greater tendency for [Formula: see text]-phase formation.

Synthesis, characterisation and reactions of cationic complexes of Arylantimony (III) chlorides ArnSbCl3-n with perchlorate and tetrafluoroborate anions

Several hitherto unreported cationic complexes of the general formula [Ar2SbL][Y] and [ArSbL2][Y]2 [ Where, Ar = C6H5, L = α-Picoline, Pyridine, Ph3AsO, hexamethyl phosphoramide (HMPA), thiourea (TU) and Y = ClO4− BF4− ] have been synthesized and characterized by solid state IR, 1H NMR, elemental analysis, conductance and molecular weight measurements. The physico-chemical data, cations [Ar2SbL]+1 and[ArSbL2]+2 are assigned a pyramidal structure.DOI: http://dx.doi.org/10.3126/ijasbt.v1i2.8204 Int J Appl Sci Biotechnol, Vol. 1(2): 42-49

Two methods of estimating competitiveness of chemosterilized males of Musca domestica (Diptera: Muscidae)

Mating competitiveness and sexual or total competitiveness of males of the house fly, Musca domestica Linnaeus, treated with 1.0% hexamethyl phosphoramide (hempa) were measured quantitatively from direct observations and ratio test methods, respectively. From direct observations, treated males of Cooper and Boxted strains of M. domestica were found to obtain more first matings than untreated males (P <0.01 and P <0.05, respectively) when competing for untreated females, whilst by using the ratio test method under laboratory conditions, total competitiveness values (C) of treated males of the two strains were estimated to be 0.72–0.89 and 0.75–0.97, respectively, at three different ratios from 1:1:1 to 3:1:1.

Total synthesis of tetracyclic sesquiterpenoids: (±)-ishwarone

A stereoselective total synthesis of the racemic modification of the tetracyclic sesquiterpenoid ishwarone (2) is described. Treatment of the known ketal aldehyde 19 with dibromomethylenetriphenylphosphorane gave the dibromo alkene 20, which was transformed efficiently into the propargylic alcohol 21. The latter compound was converted via the intermediates 22–24 into the octalone 12, which in turn was transformed by standard methodology into the corresponding ketal 7. Treatment of 7 with bromoform–aqueous sodium hydroxide in the presence of a phase-transfer catalyst, followed by acid hydrolysis of the resultant crude product, gave the crystalline keto dibromide 27. When a solution of the corresponding ketal 26 in tetrahydrofuran–hexamethyl-phosphoramide containing methyl iodide was treated with tert-butyllithium, the monobromo ketals 28 (58%) and 29 (38%) were formed. Compound 28 was converted by means of conventional reactions into the keto alcohol 32. Attempts to transform the latter substance into (±)-ishwarone (2) proved unsuccessful. When the olefinic ketal 7 was allowed to react with dimethyl diazomalonate in the presence of copper bronze, the diester 44 was produced in good yield. The latter intermediate was converted via standard methodology into the keto dimesylate 47 which, upon reaction with lithium chloride in ether–hexamethylphosphoramide, gave the corresponding dichloride 48. Treatment of 48 with potassium tert-butoxide in tetrahydrofuran resulted in an intramolecular alkylation to provide the tetracyclic keto chloride 50. Reduction of 50 with lithium triethylborohydride in tetrahydrofuran afforded (±)-ishwarol (51) which, upon oxidation with pyridinium chlorochromate in dichloromethane, furnished (±)-ishwarone (2).