| 1. |
- Adebahr, Josefina, 1973, et al.
(författare)
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Lithium coordination and mobility in gel electrolytes based on an acrylate polymer with ethylene oxide side chains
- 2003
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501 .- 0959-9428. ; 13:4, s. 814-817
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Tidskriftsartikel (refereegranskat)abstract
- Multinuclear NMR has been used to investigate the structure and mobility of a series of polymer gel electrolytes. The co-polymers used as matrixes in the gels have acrylate backbones and side chains of ethylene oxide, where the length of the side chains has been varied, while the ratio of acrylate to ethylene oxide has been kept constant. The electrolyte is a mixture of lithium perchlorate and two solvents, ethylene carbonate and gamma butyrolactone. 13 C spectra of the different gel electrolytes shows that both solvents interact with the salt, and that the strength of the interaction increases with decreasing length of the polymer side chains. It also appears that the lithium ions show no selectivity between the two types of solvent. Furthermore, the lithium chemical shift moves progressively upfield with increasing length of the side chains, showing a gradual change in interaction from lithium-solvent to lithium-(ethylene oxide).
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| 2. |
- Dahlstedt, Emma, et al.
(författare)
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Synthesis of tetrathiafulvalenes suitable for self-assembly applications
- 2004
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 14:1, s. 81-85
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Tidskriftsartikel (refereegranskat)abstract
- A series of new tetrathiafulvalenes, with double alkylthiol or alkyldisulfide substitution, have been prepared with a synthetic procedure that allows variation of different substituents. The target compounds 6a-e and 15e-i are sparsely soluble in organic solvents, but TTFs 6d and 15g gave a relatively dense packed monolayer upon exposure to gold surfaces.
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| 3. |
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| 4. |
- Desroches, C, et al.
(författare)
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Synthesis, characterization and optical power limiting behaviour of phenylazo- and 4-nitrophenylazo-tetrahydroxytetrathiacalix[4]arene
- 2001
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Ingår i: Journal of Materials Chemistry. - 0959-9428 .- 1364-5501. ; 11:12, s. 3014-3017
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Tidskriftsartikel (refereegranskat)abstract
- p-Tetrakis(4-nitrophenylazo) tetrahydroxytetrathiacalix[4] arene and p-tetrakis(phenylazo) tetrahydroxytetrathiacalix[4] arene were prepared and fully characterized using H-1 and C-13 NMR, mass spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The solid-state structure of p-tetrakis(4-nitrophenylazo) tetrahydroxytetrathiacalix[4] arene was investigated by single crystal X-ray diffraction. It crystallized in the triclinic system (space group: P (1) over bar). z-Scan experiments were performed on the p-tetrakis(4-nitrophenylazo) tetrahydroxytetrathiacalix[ 4] arene showing non linear absorption due to two photon absorption with a TPA cross-section of about 50 x 10(-50) cm(4) s per photon. Optical power limiting measurements on the p-tetrakis( phenylazo) tetrahydroxytetrathiacalix[ 4] arene at 532 nm (48% linear transmission) was found to limit the energy to similar to9 muJ.
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| 5. |
- Every, Hayley A, et al.
(författare)
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Room temperature fast-ion conduction in imidazolium halide salts
- 2001
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Ingår i: Journal of Materials Chemistry Articles. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 11:3031-6
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Tidskriftsartikel (refereegranskat)abstract
- Fast-ion conduction has been observed in the iodide and bromide salts of 1-methyl-3-ethylimidazolium at ambient temperatures. The melting point of these two compounds is above 350 K and even at 273 K the ionic conductivity in the solid-state is greater than 10–3S cm–1. Cation diffusion coefficients have been measured using fringe field gradient and/or pulse field gradient 1H NMR techniques, which indicated cation diffusion coefficients of the order of 10–10 m2 s–1 in the solid-state. Remarkably, these values are up to an order of magnitude higher than the cation diffusion coefficient in the supercooled liquid at 293 K. The activation energy for diffusion in the solid-state is extremely small, as is typical of solid-state fast-ion conductors and indicates a change in transport mechanism from the melt to the crystal. The inability to detect an 127I signal together with the modelling of the conductivity using the Nernst–Einstein equation suggests that the solid-state conduction is primarily due to cation diffusion. The solid-state fast-ion conduction is most likely related to vacancy diffusion along the cation layers in the crystal. The temperature dependence of the NMR signal intensity indicates that the number of mobile species is increasing with increasing temperature with an activation energy of approximately 20–30 kJ mol–1.
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| 6. |
- Grins, J., et al.
(författare)
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Synthesis and magnetic susceptibility of the rutile phase MnTaO4
- 2000
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 10:9, s. 2197-2200
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Tidskriftsartikel (refereegranskat)abstract
- The Mn3+-containing oxide MnTaO4 was synthesized at 1050 degrees C and 2 kbar partial oxygen gas pressure. It has a rutile-type structure, space group P4(2)/mnm, with a = 4.7189(3), c = 2.9843(3) Angstrom, and a statistical distribution of Mn/Ta. The structure was refined by the Rietveld method using both X-ray and neutron powder diffraction. The refinements, and energy-dispersive X-ray microanalysis, indicate that the phase may contain a small amount of Mn4+ and have the actual composition Mn1.08(2)Ta0.92(2)O4. The magnetic susceptibility shows a maximum at 16 K and Curie-Weiss behavior at higher temperatures, with mu(eff) = 5.11(4) mu(B) per Mn atom. The susceptibility is consistent with spin-glass behavior: (i) the temperature at the susceptibility maximum is frequency-dependent and (ii) field cooled and zero-field cooled susceptibility curves differ below the maximum. Neutron powder diffraction data collected at 10 K does not show any sharp magnetic reflections, but a very broad reflection, with a full width at half maximum height of 7 degrees, at a position corresponding to the 100 reflection is seen.
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| 7. |
- Hotta, Y, et al.
(författare)
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Coated polystyrene particles as templates for ordered macroporous silica structures with controlled wall thickness
- 2003
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Ingår i: Journal of Materials Chemistry. - 0959-9428 .- 1364-5501. ; 13, s. 496-501
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Tidskriftsartikel (refereegranskat)abstract
- Polystyrene (PS) colloidal particles have been used as templates to produce ordered macroporous silica structures. The silica films were deposited from ethanol solution containing acidic water and tetraethyl orthosilicate. The silica-coated PS spheres were characterized using transmission electron microscopy, and the film thickness determined by scanning electron microscopy and calculated from the relative weight of silica remaining after calcination. We found that the thickness of the silica film increased rapidly with time and reached a maximum that varied from 40 to 15 nm at pH 1.5 and 3, respectively. The data could be fitted to a simple first-order equation and the reaction rate and maximum thickness were related to the hydrolysis and condensation rate, respectively. Ordered macroporous structures were formed by centrifuging silica-coated PS spheres. Calcination of the close-packed spheres yielded a continuous silica matrix consisting of a three-dimensional well-ordered network of monodisperse pores
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| 8. |
- Huang, Z. L., et al.
(författare)
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Novel heterocycle-based organic molecules with two-photon induced blue fluorescent emission
- 2003
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 13:4, s. 708-711
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Tidskriftsartikel (refereegranskat)abstract
- Two-photon absorption and two-photon induced blue emission characteristics of a series of heterocycle-based organic molecules are investigated experimentally and by quantum-chemical computations. The molecules consist of a typical A-pi-A' structure, where heterocycle, styryl and formyl groups are employed as A, pi-conjugated and A' moieties, respectively. Experimental results indicate that significant enhancements in the blue emission efficiency and two-photon absorption cross-sections can be achieved by replacing S and O atoms with an N atom in the heterocycle acceptor moiety, which is also supported by the quantum-chemical computations. Additionally, larger two-photon absorption cross-sections can be obtained by choosing appropriate solvents, as indicated by the computations.
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| 9. |
- Jankova, K, et al.
(författare)
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Ion conducting solid polymer electrolytes based on polypentafluorostyrene-b-polyether-b-polypentafluorostyrene prepared by atom transfer radical polymerization
- 2004
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501 .- 0959-9428. ; 14:19, s. 2902-2908
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Tidskriftsartikel (refereegranskat)abstract
- Novel triblock copolymers based on central poly( ethylene glycol) ( PEG) or poly( ethylene glycol-co-propylene glycol) (PEGPG) blocks with poly( pentafluorostyrene) (PFS) outer blocks were prepared by Atom Transfer Radical Polymerization (ATRP) with polydispersities on the order of 1.2 - 1.3. The bromoisobutyrate functionalized polyether macroinitiators with molecular masses (M-n) of approx. 10 000 enabled the addition of between 15 and 39 wt.% flanking PFS as found by H-1 NMR. In a similar fashion monomethoxy PEG ( MPEG, Mn 5 000) was added 50 wt.% PFS. Polymer electrolytes were prepared by complexing lithium bis( trifluoromethylsulfonyl) imide salt with the block copolymers and the liquid PEGPG precursor. The crystallinity and the melting points of the salted MPEG-b-PFS and triblock copolymers were found by DSC to be substantially suppressed. Short PFS blocks (T-g 33 degreesC) and the salted PEGPG blocks (T-g -65 degreesC) were immiscible and resulted in phase separation providing an elastomeric material in form of a physically cross-linked polyether network, even when the PFS block consisted of only about four monomer units. The salted triblock copolymers of PEGPG demonstrated conductivities of 10(-5.1) to 10(-4.9) S cm(-1) at 20 degreesC.
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| 10. |
- Jannasch, Patric
(författare)
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Porous polymaleimide networks
- 2001
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501 .- 0959-9428. ; 11:9, s. 2303-2306
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Tidskriftsartikel (refereegranskat)abstract
- Porous network structures were prepared by in situ polymerisation of a mixture of N-phenylmaleimide and 1, 1'-(methylenedi-4,1-plienylene)bismaleimide (95:5 w/w) in poly(vinylidene difluoride-co-hexafluoropropylene) (PVDH). The mixture of the maleimide monomers was found to form thermoreversible gels with PVDH. Thermodynamic analysis of the gelation process using calorimetry data indicated the formation of complexes of N-phenylmaleimide and vinylidene difluoride repeat units with a molar ratio of 1:2, respectively. PVDH formed optically clear solutions in the mixture above the gelation temperature, observed at 80-120 degreesC depending on composition. Polymerisation of the maleimides was induced by increasing the temperature to 250 degreesC. During polymerisation, the resulting polymaleimide phase separated from the PVDH melt. A morphological study by microscopy revealed that blends with 80 wt% PVDH contained continuous networks of crosslinked polymaleimide. The porous networks were collected after removing the PVDH by solvent extraction. Thermogravimetrical analysis of the polymaleimide networks under N-2 atmosphere showed that the onset of weight loss occurred at 380 degreesC. These networks may thus be used to prepare thermally stable membranes.
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| 11. |
- Johansson, Tomas, et al.
(författare)
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Electrochemical bandgaps of substituted polythiophenes
- 2003
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 13:6, s. 1316-1323
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Tidskriftsartikel (refereegranskat)abstract
- The electrochemical bandgaps for different soluble substituted polythiophenes have been measured by cyclic voltammetry. The effect of substituents on the oxidation/reduction potentials is discussed. Bandgaps obtained by cyclic voltammetry have been found to be in general higher than optical bandgaps. Among regioregular polymers substituted with a phenyl group at position 3 of the thiophene ring, examples are found that give very symmetric voltammograms. Rationalization for this behaviour is discussed from a conformational point of view.
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| 12. |
- Munch Elmér, Anette, et al.
(författare)
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Ion Conductive Electrolyte Membranes Based on Co-Continuous Polymer Blends
- 2003
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501. ; 13:9, s. 2168-2176
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Tidskriftsartikel (refereegranskat)abstract
- Solid electrolyte membranes based on comb-shaped poly(ethylene glycol) (PEG) doped with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt in blends with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) have been studied. Membranes containing between 70 and 100 wt% PEG were prepared by a convenient two-step process where films containing a mixture of mono- and dimethacrylate-terminated PEG macromonomers, PVDF-HFP, LiTFSI, and a photoactivator were cast from acetone solutions, followed by UV-initiated polymerization of the macromonomers. Microscopy of the membranes revealed a phase separated morphology with a microporous PVDF-HFP network embedded in comb-shaped PEG. The membranes were thermally stable at temperatures below the melting point of PVDF-HFP at 140 °C. Dynamic mechanical analysis (DMA) in the tension mode showed that the mechanical properties of the membranes were greatly improved both by the addition of PVDF-HFP and of dimethacrylate-terminated PEG macromonomer. For example, the storage modulus at 25 °C and 1 Hz showed a three-fold increase after increasing the percentage of dimethacrylate-terminated PEG from 0 to 10 wt% in the macromonomer mixture. A broad shoulder on tan as a function of temperature indicated the existence of a PVDF-HFP rich amorphous interphase. At room temperature, the membranes containing more than 80 wt% PEG reached ionic conductivities exceeding 10–5 S cm–1.
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| 13. |
- Peng, Hong, et al.
(författare)
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Reaction sequences occurring in dense Li-doped sialon ceramics : influence of temperature and holding time
- 2003
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Ingår i: Journal of Materials Chemistry. - 0959-9428 .- 1364-5501. ; 13:9, s. 2285-2289
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Tidskriftsartikel (refereegranskat)abstract
- Spark Plasma Sintering (SPS) has been used to consolidate a lithium-doped duplex α–β sialon with the overall composition Li0.5Si9.5Al2.5O2.0N14. The kinetics of densification has been studied, and the phase transformation, reactions and grain growth occurring in the dense compacts upon further heat treatment have been investigated. Two sources of Si3N4 powders were used, namely α- and β-Si3N4. Green bodies heated at a rate of 100 °C min−1 yielded fully dense compacts at 1450 °C (α-Si3N4) and 1500 °C (β-Si3N4) without holding, and these compacts consisted mainly of a locally formed liquid and precursor Si3N4 particles. Upon further heating it was observed that α-sialon is formed initially, irrespectively of whether α-Si3N4 or β-Si3N4 powder is used as Si3N4 source; and when α-Si3N4 is used as starting powder, almost monophasic α-sialon compacts are formed before any transformation to β-sialon takes place on further heating. When β-Si3N4 is used as starting powder the formation of β-sialon is kinetically promoted, and compacts containing α-sialon, β-sialon and β-Si3N4 are obtained before the equilibrium phase assemblage is reached, i.e. a lithium-doped duplex α–β sialon ceramic. These observations can be interpreted in terms of the Ostwald step rule. Grain growth does not occur until the equilibrium phase assemblage has been established. The separation of grain growth from densification and phase transformation has implications for preparing Si3N4-based nano-ceramics and provides possibility for further studies of the kinetics of grain growth in Si3N4-based ceramics.
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| 14. |
- Spiers, H, et al.
(författare)
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Self propagating high temperature synthesis of magnesium zinc ferrites (MgxZn1-xFe2O3): thermal imaging and time resolved X-ray diffraction experiments
- 2004
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501. ; 14:7, s. 1104-1111
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Tidskriftsartikel (refereegranskat)abstract
- Spinel ferrites of the form MgxZn1-xFe2O4 ( x = 0. 0.25, 0.50, 0.75, 1.00) were prepared by self-propagating high-temperature synthesis (SHS) from reactions of iron(III), zinc and magnesium oxides, iron powder and sodium perchlorate. The driving force for the reactions is the oxidation of iron powder. Reactions were carried out in the presence of an external magnetic field of 0.2 or 1.1 T. Reaction velocity and temperatures were obtained by thermal imaging camera. The transformation of reactants to products was studied by time resolved X-ray diffraction using Rietveld refinement for determination of phase percentages. Reactions typically reached temperatures in excess of 1150 degreesC with a timescale of complete conversion of reactant to products of 20 s. All materials were characterised by X-ray powder diffraction (XRD), energy dispersive X-ray analysis (EDXA), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Mossbauer spectroscopy and vibrating sample magnetometry (VSM).
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| 15. |
- Tosheva, Lubomira, et al.
(författare)
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Amorphous very high surface area silica macrostructures
- 2000
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 10:10, s. 2330-2337
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Tidskriftsartikel (refereegranskat)abstract
- A procedure for the preparation of amorphous silica spherical macroparticles using strongly basic anion exchange gel resins as shape directing macro-templates is presented. Resin beads were hydrothermally treated with either clear homogeneous TPA–silicate solutions containing tetraethoxysilane, tetrapropylammonium hydroxide and distilled water or with sodium silicate solutions. As a result of the ion exchange of silica species into the resin structure, resin–silicate composites were formed. After separation and drying of the resin–silicate composites, the resin was removed by combustion leaving solid spherical silica particles with surface areas exceeding 1000rm2rgm1. Two types of gel resins having different active groups and degrees of cross-linking were employed and the products obtained were characterised by SEM, Raman spectroscopy and nitrogen adsorption measurements. The type of the resin as well as the type of silicate solution used were of great importance for the pore structure of the final materials.
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| 16. |
- Wang, Z., et al.
(författare)
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Peroxo sol-gel preparation : Photochromic/electrochromic properties of Mo-Ti oxide gels and thin films
- 2000
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 10:10, s. 2396-2400
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Tidskriftsartikel (refereegranskat)abstract
- Metallic Mo powder and Ti(OBu(n))4 were separately dissolved in H2O2 solution and the solutions obtained mixed in different Mo/Ti atomic ratios to prepare precursor solutions. Fresh gels obtained from the precursor solutions with >40% Mo became blue upon exposure to ambient light. X-Ray photoelectron spectroscopy (XPS) was used to examine the chemical states and compositions of the resultant blue-tinged xerogel powders. Based on the XPS results, it is proposed that TiO2 particles and surface species, including adsorbed water and organic residue, all contribute to the photochromic effect of MoO3. Mo-Ti oxide films were spin-coated on ITO-coated glass substrates using a precursor solution containing 70% Mo. The cycling behaviours of the films annealed at 150°C for 1 h were studied using cyclic voltammetry (CV) in propylene carbonate solution containing I mol L-1 LiClO4. The electrochromic properties of the films upon lithium intercalation were investigated by in situ monochromatic transmittance measurements during the CV process, as well as ex situ in the UV/Vis region. The Mo-Ti oxide films were found to possess excellent electrochromic properties upon Li+ ion insertion/extraction.
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| 17. |
- Yilmaz, Ecevit, et al.
(författare)
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A facile method for preparing molecularly imprinted polymer spheres using spherical silica templates
- 2002
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 12:5, s. 1577-1581
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Tidskriftsartikel (refereegranskat)abstract
- A novel and facile preparation method for spherical molecularly imprinted polymer (MIP) beads is presented. Two types of beads were synthesized and investigated: (i) silica-MIP composites were obtained by filling spherical, porous C-4-coated silica beads with print molecule and monomers followed by polymerisation; (ii) spherical molecularly imprinted polymer beads were acquired mirroring the silica particles in size, shape and pore structure by removing the silica matrix from the silica-MIP composites. With regard to their chromatographic properties and yield of the materials both types of particle were more advantageous compared to irregularly shaped traditional MIPs. Also the work-up time to obtain imprinted spherical particles is greatly reduced compared to traditional methods using polymer monoliths, which have to be ground, sieved and sedimented. Generally, the described method may open new possibilities for synthesis of novel types of imprinted polymer formats such as membranes, bulk polymers, films or in-situ columns using appropriate support or sacrificial materials.
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