Ionic conductivity in the crystalline polymer electrolytes PEO6:LiXF6, X = P,As, Sb

Ionically conducting polymers (salts dissolved in a polymer matrix) are of great interest because they uniquely exhibit ionic conductivity in a soft but solid membrane. As such, they are critical to the development of devices such as all-solid-state lithium batteries. The established view of ionic conductivity in polymer electrolytes is that this occurs in amorphous materials above their glass transition temperature and that crystalline polymer electrolytes are insulators. In contrast, we show that three crystalline polymer electrolytes, poly(ethylene oxide)(6):LiXF(6), X = P, As, Sb, not only conduct but do so better than the analogous amorphous phases! It is also shown that the conductivities of all three 6:1 complexes are similar, consistent with the dimension of the bottlenecks to conduction derived from their crystal structures. An increase in ionic conductivity with reduction of molecular weight of the crystalline polymer electrolyte (from 2000 to 1000) is reported and shown to relate to the increase in crystallite size on reducing molecular weight.     

Hadamard 2-(63,31,15) designs invariant under the dihedral group of order 10

All Hadamard 2-(63,31,15) designs invariant under the dihedral group of order 10 are constructed and classified up to isomorphism together with related Hadamard matrices of order 64. Affine 2-(64,16,5) designs can be obtained from Hadamard 2-(63,31,15) designs having line spreads by Rahilly’s construction [A. Rahilly, On the line structure of designs, Discrete Math. 92 (1991) 291-303]. The parameter set 2-(64,16,5) is one of two known sets when there exists several nonisomorphic designs with the same parameters and p-rank as the design obtained from the points and subspaces of a given dimension in affine geometry AG(n,p^m) (p a prime). It is established that an affine 2-(64,16,5) design of 2-rank 16 that is associated with a Hadamard 2-(63,31,15) design invariant under the dihedral group of order 10 is either isomorphic to the classical design of the points and hyperplanes in AG(3,4), or is one of the two exceptional designs found by Harada, Lam and Tonchev [M. Harada, C. Lam, V.D. Tonchev, Symmetric (4, 4)-nets and generalized Hadamard matrices over groups of order 4, Designs Codes Cryptogr. 34 (2005) 71-87].     

Structure, stoichiometry and transport properties of lithium copper nitride battery materials: combined NMR and powder neutron diffraction studies

A combined NMR and neutron diffraction study has been carried out on three Li(3-x-y)Cu(x)N materials with x=0.17, x=0.29 and x=0.36. Neutron diffraction indicates that the samples retain the P6/mmm space group of the parent Li(3)N with Cu located only on Li(1) sites. The lattice parameters vary smoothly with x in a similar fashion to Li(3-x-y)Ni(x)N, but the Li(2) vacancy concentration for the Cu-substituted materials is negligible. This structural model is confirmed by wideline (7)Li NMR spectra at 193 K which show three different local environments for the Li(1) site, resulting from the substitution of neighbouring Li atoms in the Li(1) layer by Cu. Since the Cu-substituted materials are only very weakly paramagnetic, variable temperature (7)Li wideline NMR spectra can be used to measure diffusion coefficients and activation energies. These indicate anisotropic Li(+) diffusion similar to the parent Li(3)N with transport confined to the [Li(2)N] plane at low temperature and exchange between Li(1) and Li(2) sites dominant at high temperature. For the intra-layer process the diffusion coefficients at room temperature are comparable to Li(3)N and Li(3-x-y) Ni(x)N, while E(a) decreases as x increases in contrast to the opposite trend in Ni-substituted materials. For the inter-layer process E(a) decreases only slightly as x increases, but the diffusion coefficients at room temperature increase rapidly with x.     

Copper(II) Complexes of Spirohydantoins. Synthesis,Quantum-Chemical,and Spectroscopic Study

A series of new Cu(II) complexes with important physiologically active cycloalkane-5-spirohydantoines are synthesized reacting as a result of CuCl₂ · 2H₂O interaction with the ligands in alkaline water medium. Their structures were studied using spectroscopic (IR and EPR) methods. For comparison, ab initio calculations of the structure and IR spectra of the corresponding Cu(II) complexes were also performed. It was proven that with cyclopentane-5-spirohydantoins, distorted (flattened) tetrahedral structure is realized Cu(L_–H)₂(H₂O)₂, while with the higher cycloalkane-5-spirohydantoins linear Cu(II) complexes of the type CuL_–H(OH) are formed.     

Anionically prepared poly(ε-caprolactam-co-ε-caprolactone) and poly(ε-caprolactam-co-δ-valerolactone) copolymers: Thermal and mechanical properties

Thermal and representative physico-mechanical properties of newly prepared poly[(ε-caprolactam)-co-(ε-caprolactone)] and poly[(ε-caprolactam)-co-(δ-valerolactone)] copolymers were studied. The copolymers were synthesized by anionic polymerization of ε-caprolactam activated by isocyanate end-capped oligomeric aliphatic polyesters designated as the macroactivators (MAs). Type, concentration and molecular weight of the MAs were varied, which resulted in copolymers with different structure and properties. The impact of the new MAs used in this study on the glass transition temperature and the melting temperature of poly-ε-caprolactam was investigated by DSC. DMTA was used to analyze the effect of copolymerization on the storage modulus (E^′) and tan δ of poly-ε-caprolactam. Conventional and high-resolution TGA data revealed that all the synthesized polyesteramides possess good thermal stability. Mechanical properties were studied by notched impact and tensile testing. According to the experimental data the impact toughness increase with the MA content, being six time higher compared to the poly(ε-caprolactam) in the best situation. Water absorption was also considered in relation to the composition of the copolymers.     

Crystal chemistry and electronic structure of the metallic lithium ion conductor, LiNiN

The layered ternary nitride LiNiN shows an interesting combination of fast Li+ ion diffusion and metallic behavior, properties which suggest potential applications as an electrode material in lithium ion batteries. A detailed investigation of the structure and properties of LiNiN using powder neutron diffraction, ab initio calculations, SQUID magnetometry, and solid-state NMR is described. Variable-temperature neutron diffraction demonstrates that LiNiN forms a variant of the parent Li3N structure in which Li+ ion vacancies are ordered within the [LiN] planes and with Ni exclusively occupying interlayer positions (at 280 K: hexagonal space group Pm2, a = 3.74304(5) A, c = 3.52542(6) A, Z = 1). Calculations suggest that LiNiN is a one-dimensional metal, as a result of the mixed pi- and sigma-bonding interactions between Ni and N along the c-axis. Solid-state 7Li NMR spectra are consistent with both fast Li+ motion and metallic behavior.     

Synthesis and characterization of fluorinated telomers containing vinylidene fluoride and hexafluoropropene from 1,6‐diiodoperfluorohexane

The synthesis of original fluorinated (co)telomers containing vinylidene fluoride (VDF) or VDF and hexafluoropropene (HFP) was achieved by radical telomerizations and (co)telomerizations of VDF (or VDF and HFP) in the presence of 1, 6‐diiodoperfluorohexane via a semisuspension process. tert‐Butyl peroxypivalate (TBPPi) was used as an efficient thermal initiator. The numbers of VDF and VDF/HFP base units in the (co)telomers were determined by ¹⁹F and ¹H NMR spectroscopy. They ranged from 10 to 190 VDF base units. Fluorinated telomers of various molecular weights (1200–12,600 g/mol) were obtained by the alteration of the initial [1,6‐diiodoperfluorohexane]₀/[fluoroalkenes]₀ and [TBPPi]₀/[fluoroalkenes]₀ molar ratios. The thermal properties of these fluorinated (co)telomers, such as the glass‐transition temperature and melting temperature, were examined. As expected, these telomers exhibited good thermal stability. They were stable at least up to 350 °C. The compounds containing more than 30 VDF units were crystalline, whereas all those containing VDF‐co‐HFP were amorphous with elastomeric properties, whatever the number was of the fluorinated base units. The structures of I–(VDF)_n–R_F–(VDF)_m–I and I–(HFP)_x(VDF)_n–R_F–(VDF)_m(HFP)_y–I (co)telomers were obtained, and the defects of the VDF chain and the ? CH₂CF₂I and ? CF₂CH₂I functionalities were studied successfully (where R_F = C₆F₁₂). The functionality in the iodine atoms was modified: the higher the VDF content in the telomers, the lower the normal end functionality (? CH₂CF₂I) and the higher the reversed extremity (? CF₂CH₂I). In addition, the percentage of defects increased when the number of VDF units increased. The molecular weights and molecular weight distributions of different telomers and cotelomers were also studied. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1470–1485, 2006     

Line spreads of PG(5, 2)

All line spreads of PG(5, 2) are constructed and classified up to equivalence by exhaustive generation considering the specific properties of the automorphism group, and the participation of the spread lines in the subspaces of dimension 3. There are 131,044 inequivalent spreads. The orders of the automorphism groups preserving the spreads, and the 2‐ranks of the related by Rahilly's construction affine 2‐(64,16,5) designs are also computed. © 2008 Wiley Periodicals, Inc. J Combin Designs 17: 90–102, 2009     

Plasmon microscopy and imaging ellipsometry of Artrobacter oxydans attached on polymer films

The attachment of Artrobacter oxydans 1,388 on a newly synthesized biodegradable copolymer of poly-(hexanlactam)-co-block-poly-(delta-valerolactone) is investigated by optical, microscopic and biochemical methods. The potentials of surface plasmon microscopy and imaging ellipsometry for detecting microorganisms when Al films are used to excite plasmons is assessed by comparing images obtained by these methods with dark field microscopy pictures. The experimental results demonstrate that in this case imaging ellipsometry and plasmon microscopy in transmission are promising methods and can be used in optical sensors for monitoring cell adhesion.