Michael John Smith

The effects of radiation-induced crosslinking on the conductance of LiClO4·PEO electrolytes

The conductance/temperature behaviour of poly(ethylene oxide)/LiClO4 electrolyte prepared under anhydrous conditions has been studied. Amorphous electrolyte samples have been crosslinked using γ-radiation from a Co-60 source. It is shown that light crosslinking cause a small reduction in the conductivity, probably due to restricted backbone segmental motion; however the tendency of electrolyte, treated in this way, to transform to a mixed crystalline/amorphous state of much lower conductivity, seems to have been comletely eliminated.

A novel class of luminescent polymers obtained by the sol–gel approach

A series of amorphous Eu3+-doped hybrid organic/inorganic materials prepared by the sol–gel process is presented. The host matrix of the so-called ureasils is a silica network to which oligopolyoxyethylene chains are grafted by means of urea bonds. Trivalent europium is present as a triflate salt, Eu(CF3SO3)3. Four different compositions of salt have been considered: n=184, 92, 55 and 37, where n represents the number of (OCH2CH2) polymer repeat units per ion group of Eu(CF3SO3)3. Infrared spectroscopic studies suggest that the doped ureasils contain both free and coordinated triflate ions. The lowest decomposition temperature (about 250°C) occurs with composition n=92. This composition also exhibits the highest conductivity at room temperature (approximately 10−5 Ω−1 cm−1). The photoluminescence spectra of these materials present a series of narrow lines assigned to 5D0→7F0,1,2,3,4 transitions. The high emission intensity observed is a promising property for application of the ureasils in technological luminescent devices.

Ionic interactions in MCF3SO3-polyether complexes containing mono-, di- and trivalent cations

Ion association has been investigated by Raman scattering from triflate salts M (CF 3 SO 3 ) x in PEO (400) for various cationic substitutions (M=li + , Ca 2+ , Cu 2+ , and Nd 3+ ) and for OH-capped, respectively CH 3 -capped, polymer chains. The ion-ion interaction shows different temperature behavior in different systems. The observations are discussed in terms of recent theories which consider volume changes (electrostriction) in the salt dissociation process

Preparation and characterization of a lithium ion conducting electrolyte based on poly(trimethylene carbonate)

Abstract In this paper, the results of preliminary studies of two new solvent-free polymer electrolytes based on poly(trimethylene carbonate), p(TMC), with lithium trifluoromethanesulphonate, (triflate), and lithium perchlorate are described. Thin films of these electrolytes were obtained by evaporation of solvent from homogeneous mixtures of known masses of host polymer and salt. Electrolytes with compositions of n between 1.5 and 85, where n represents the molar ratio of (OCOCH2CH2CH2O) units per lithium ion, have been prepared. These solvent-free electrolytes were characterized by measurements of total ionic conductivity, differential scanning calorimetry (DSC) and thermogravimetry (TGA). As expected from previous studies with these salts in poly(ethylene oxide), PEO, the triflate-based system showed superior thermal stability but with a lower total ionic conductivity than that of the perchlorate-containing electrolyte. The highest conductivity (approximately 3×10−4 Ω−1 cm−1) was found at 95°C with the electrolyte composition of (TMC)2LiClO4.

Sol-gel processing and structural study of europium-doped hybrid materials

The thermal, morphological and conducting properties of macromolecular organic-inorganic networks synthesized by the sol-gel process and containing a wide concentration range of europium trifluoromethanesulfonate, Eu(CF 3 SO 3 ) 3 , have been investigated. The hybrid matrix, U(2000), of these materials, classed as ureasils, includes a siliceous backbone and short polyether-based segments. The link between these components is made by urea bridges. The behaviour of the doped ureasils is significantly better than that of previously characterized electrolytes based on poly(ethylene oxide), PEO. The essentially amorphous character of the hybrid host contributes to an improved transparency and moderate conductivities of certain electrolytes at room temperature (ca. 5×10 –6 Ω –1 cm –1 ). DSC, XRD and FTIR measurements show that the formation of a high-melting crystalline complex results from the coordination of the Eu 3+ ions by the ether oxygens of the organic moieties at composition n=5 [where n represents the molar ratio of (OCH 2 CH 2 ) units per Eu 3+ ion]. The results obtained for samples with n≥20 suggest that in this range of composition the principal effect of the polyether chains is to exert a plasticizing influence, as the coordination of the cations by the urea linkages is favored.

An interesting ligand for the preparation of luminescent plastics: The picrate ion

Electrolytes formed with poly(oxyethylene), POE, and europium picrate, [Eu(pic)2(OH2)6]pic.6H2O (where pic denotes the picrate anion) or simply Eu(pic)3xH2O, have been investigated by infrared and photoluminescence spectroscopies. The complexes have been represented by POEnEu(pic)3xH2O (where n represents the molar ratio of (OCH2CH2) units per Eu3+ ion). Materials with n ranging from 133 to 11 have been examined. A tentative attribution for the absorption bands of the mid-infrared spectra is presented. The spectral changes detected in the mid-infrared region and the modifications observed in the XRD patterns at increasing salt content show that Eu(pic)3xH2O exerts an effective plasticizing role which leads to the complete supression of crystallinity at n=11. The emission spectra of the complexes and their signature in the νC–O spectral region provide conclusive evidence that the Eu3+ ions are coordinated to the oxygens atoms of the polyether chains over the whole range of compositions studied. The photolu...

Application of di-ureasil ormolytes based on lithium tetrafluoroborate in solid-state electrochromic displays

In this study the sol–gel synthetic strategy was used to prepare organic–inorganic hybrid electrolyte systems composed of a di-urea cross-linked poly(ethylene oxide) (PEO)/siloxane (di-ureasil) matrix with a wide concentration range of lithium tetrafluoroborate (LiBF4). The assembly and preliminary characterization of a prototype solid-state electrochromic device based on a four-layer sandwich structure incorporating these hybrid electrolytes doped with controlled quantities of LiBF4 are reported. The composition of hybrid xerogels was indicated using the notation d-U(900)nLiBF4 and d-U(600)nLiBF4. In this representation the average molecular weight of the host di-ureasil framework is identified as d-U(900) or d-U(600) and the subscript n expresses the salt content in terms of the number of ether oxygen atoms per Li+ cation. The most conducting electrolyte of these hybrid systems is the d-U(900)35LiBF4 composition (1.70 × 10−4 S cm−1 at about 95 °C). The lowest decomposition temperature was observed at a composition of n = 2.5 in both the d-U(900)nLiBF4 and the d-U(600)nLiBF4 electrolyte systems (250 °C and 243 °C, respectively). Electrochromic devices assembled with d-U(900)nLiBF4 and d-U(600)nLiBF4 electrolytes with compositions of 20 ≤ n ≤ 35 presented good color contrast, a maximum optical density of 0.23 and an encouraging performance in the coloring/bleaching process. The average transmittance in the visible region of the spectrum was above 74% for all the bleached samples analyzed.

Thermal properties and ionic conductivities of lanthanide-based ormolytes

Abstract Hybrid organic/inorganic networks doped with europium triflate, Eu(CF 3 SO 3 ) 3 , have been prepared by the sol-gel method and characterized by conductivity and thermal analysis techniques. The electrolyte films produced were obtained as transparent, amorphous monoliths with encouraging optical characteristics and moderate bulk conductivities.

Preparative effects on poly(ethylene oxide) based polymer electrolytes of lanthanide salts

Abstract A series of solid polymer electrolytes prepared from commercial poly(ethylene oxide) and lanthanide triflates (La 3+ , Nd 3+ and Eu 3+ ), in which the salt ions are solubilised by complexation with the oxygen atoms in the flexible polymer molecule, has been studied using ac conductivity and thermal analysis measurements. Two techniques, solvent casting and hot-pressing, were applied to produce a range of polymer electrolyte compositions. The differences in the behaviour of electrolytes produced using these two preparative techniques have been justified in terms of partial decomposition of the electrolytes, the effects of chain entanglement and the presence of residual solvent molecules increasing the free volume of the polymer chains.

Morphological and conductivity studies of di-ureasil xerogels containing lithium triflate

AbstractSol / gel derived poly(oxyethylene)/siloxane hybrids doped with lithium triflate, LiCF 3 SO ,have been investigated. The hosthybrid matrix of these materials, named di-ureasil and represented by U(600), is composed by a siliceous framework to whichpolyether chains containing 8.5 oxyethylene repeat units are covalently bonded through urea linkages. Xerogel samplesU(600) n LiCF 3 SO 3 with n (where n is the molar ratio of oxyethylene moieties per Li ion) between and 0.1 have beenexamined. X-ray diffraction and differential scanning calorimetry have provided conclusiveevidence that the xerogels analyzed areentirely amorphous. The salt-rich material with n / 1 exhibits the highest conductivity over the whole range of temperature analyzed(e.g. 4.3 6 / 10 and 2.0 / 10 4 V 1 cm , respectively, at 25 and 94 8C). # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Di-ureasils; Li ; X-ray diffraction; Differential scanning calorimetry; Ionic conductivity 1. IntroductionHighly conducting, thin, solvent-free electrolyte filmsmay be produced by dissolving salts in high molecularweight polymers carrying adequate coordinating species,such as ether oxygen atoms or amine nitrogen atoms [1