Effect of zwitterions on electrochemical properties of oligoether-based electrolytes

Solid polymer electrolytes show great potential in electrochemical devices. Poly(ethylene oxide) (PEO) has been studied as a matrix for solid polymer electrolytes because it has relatively high ionic conductivity. In order to investigate the effect of zwitterions on the electrochemical properties of poly(ethylene glycol) dimethyl ether (G5)/lithium bis(fluorosulfonyl) amide (LiFSA) electrolytes, a liquid zwitterion (ImZ2) was added to the G5-based electrolytes. In this study, G5, which is a small oligomer, was used as a model compound for PEO matrices. The thermal properties, ionic conductivity, and electrochemical stability of the electrolytes with ImZ2 were evaluated. The thermal stabilities of all the G5-based electrolytes with ImZ2 were above 150 °C, and the ionic conductivity values were in the range of 0.8–3.0 mS cm−1 at room temperature. When the electrolytes contained less than 5.5 wt% ImZ2, the ionic conductivity values were almost the same as that of the electrolyte without ImZ2. The electrochemical properties were improved with the incorporation of ImZ2. The anodic limit of the electrolyte with 5.5 wt% ImZ2 was 5.3 V vs. Li/Li+, which was over 1 V higher than that of G5/LiFSA.

Improvement of charge/discharge properties of oligoether electrolytes by zwitterions with an attached cyano group for use in lithium-ion secondary batteries

Zwitterions with a cyano group on the side chain (CZ) were synthesized. Although the addition of CZ caused a slightly negative effect on viscosity, ionic conductivity, limiting current density, and lithium transference number, the oxidation limit of PEGDME/lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) composites was improved to over 5 V. For charge/discharge testing using Li|electrolyte|LiCoO2 cells, the cycle stability of PEGDME/LiTFSA with CZ in the voltage range of 3.0-4.6 V was much higher than that of PEGDME/LiTFSA. Incorporating a small mole fraction of CZ into PEGDME-based electrolytes prevented an increase in the interface resistance between the electrolyte and cathode with increasing numbers of the cycle.

Novel polyvinylpyrrolidones to improve delivery of poorly-water soluble drugs; from design to synthesis and evaluation

Polyvinylpyrrolidone is a widely used in tablet formulations with the linear form acting as a wetting agent and disintegrant whereas the cross-linked form is a super-disintegrant. We have previously reported that simply mixing the commercial cross-linked polymer with ibuprofen disrupted drug crystallinity with consequent improvements in drug dissolution behavior. In this study, we have designed and synthesized novel cross-linking agents containing a range of oligoether moieties which have then be polymerized with vinylpyrrolidone to generate a suite of novel excipients with enhanced hydrogen-bonding capabilities. The polymers have a porous surface and swell in most common solvents and in water; properties which suggest their value as disintegrants. The polymers were evaluated in simple physical mixtures with ibuprofen as a model poorly-water soluble drug. The results show that the novel PVPs induce the drug to become “X-ray amorphous”, which increased dissolution to a greater extent than that seen with commercial cross-linked PVP. The polymers stabilize the amorphous drug with no evidence for recrystallization seen after 20 weeks storage.

Preparation and characterization of cross-linked starch polyurethanes

This study describes the preparation and characterization of new starch cross-linked polyurethanes produced by the reaction of native cornstarch with a propylene oxide toluene diisocyanate oligomer. Infrared analysis confirmed the occurrence of the reaction and solubility and swelling tests showed that it had led to cross-linked structures. These products were totally amorphous and displayed elastomeric properties associated with two T(g)s at -60 and 35 degrees C. (C) 2009 Elsevier Ltd. All rights reserved.