Biomedical subjects
Publications and source records attributed to Wesley A Henderson.
The crystal structures and thermal behavior of the 1-(2-methoxyethyl)-2,3-dimethylimidazolium chloride and hexa-fluorophosphate salts are compared with the analogous 1-butyl-2,3-dimethylimidazolium salts to examine the influence of the ether oxygen on salt thermal properties for a typical constituent cation used in the preparation of ionic liquids.
Phase diagrams are reported for glyme mixtures with simple lithium salts. The glymes studied include monoglyme (DME), diglyme, triglyme, and tetraglyme. The lithium salts include LiBETI, LiAsF6, LiI, LiClO4, LiBF4, LiCF3SO3, LiBr, LiNO3, and LiCF3CO2. The phase diagrams clearly illustrate how solvate formation and thermophysical properties are dictated by the ionic association strength of the salt (i.e., the properties of the anions) and chain length of the solvating molecules. This information provides critical predictive capabilities for solvate formation and ionic interactions common in organometallic reagents and battery electrolytes.
A new TFSI- anion disordering mode has been discovered in a supercooled plastic crystalline phase of Et4NTFSI, which may, in part, account for the low melting points of TFSI- salts with organic cations, thereby forming ionic liquids, and the intriguing properties of LiTFSI for lithium battery applications.
In this paper is reported an extensive NMR characterization of N-methyl-N-propyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR13TFSI) room-temperature ionic liquid and its mixtures with LiTFSI. NMR was used to investigate the interactions between the ionic liquid and lithium salt and the diffusion coefficients of all ionic species present in these mixtures. The results are compared with previous DSC, Raman, and electrochemical investigations.
The mechanisms by which ions are transported through polymer electrolytes are poorly understood. Structural information should greatly aid in the determination of such mechanisms and the optimization of the electrolyte properties. Ionic conductivity, however, predominates in amorphous polymer-salt phases, and characterization of amorphous solvate structures is difficult. The task is simplified by comparisons with crystalline poly(ethylene oxide) (PEO)-salt phases, but the structural determination of such phases is also difficult because single crystals have not been available. Here, it is demonstrated that single crystals of PEO-lithium salt phases may be prepared and characterized using low molecular weight PEO.
A procedure for the preparation of high-quality single crystals from concentrated glyme mixtures is presented. Anhydrous single crystals of LiNO(3) and LiClO(4) were prepared in this manner, and the single-crystal structure of LiClO(4) (orthorhombic, Pnma, a = 8.6447(12) A, b = 6.8512(10) A, c = 4.8254(7) A, Z = 4) was determined as an example. This procedure is expected to be widely applicable for not only salts but also a wide range of other materials solvated by glymes.
The title compounds, poly[[[bis(2-methoxyethyl) ether]lithium(I)]-di-mu(3)-trifluoromethanesulfonato-lithium(I)], [Li(2)(CF(3)SO(3))(2)(C(6)H(14)O(3))](n), and poly[[[bis(2-methoxyethyl) ether]lithium(I)]-di-mu(3)-trifluoroacetato-dilithium(I)-mu(3)-trifluoroacetato], [Li(3)(C(2)F(3)O(2))(3)(C(6)H(14)O(3))](n), consist of one-dimensional polymer chains. Both structures contain five-coordinate Li(+) cations coordinated by a tridentate diglyme [bis(2-methoxyethyl) ether] molecule and two O atoms, each from separate anions. In both structures, the [Li(diglyme)X(2)](-) (X is CF(3)SO(3) or CF(3)CO(2)) fragments are further connected by other Li(+) cations and anions, creating one-dimensional chains. These connecting Li(+) cations are coordinated by four separate anions in both compounds. The CF(3)SO(3)(-) and CF(3)CO(2)(-) anions, however, adopt different forms of cation coordination, resulting in differences in the connectivity of the structures and solvate stoichiometries.