L. C. Rodrigues

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.

K+-doped poly(ε-caprolactone)/siloxane biohybrid electrolytes for electrochromic devices

Sol-gel derived KCF3SO3-doped di-urethane cross-linked poly(-caprolactone) (PCL(530))/siloxane ormolytes with  > n  0.5 (n indicates the number of (C(=O)(CH2)5O) repeat units per K + ion) have been studied. Xerogel samples with n ≥ 1 are thermally stable up to 235 oC. A minor proportion of PCL crystallites occur in some dilute-to-concentrated samples. At n ≤ 4 a crystalline PCL(530)/siloxaneKCF3SO3 complex with unknown stoichiometry emerges. At n ≤ 2 this complex coexists with pure salt. At temperatures higher than 40 oC the composition which exhibits the highest ionic conductivity is n = 21. “Free” anions, weakly coordinated CF3SO3 ions, contact ion pairs and several higher ionic aggregates emerge in all the * Phone: 00-351-259-350253; Fax: 00-351-259-350480; E-mail: vbermude@utad..pt

Study and Characterization of a Novel Polymer Electrolyte Based on Agar Doped with Magnesium Triflate

In the present work one host natural matrix – agar – has been doped with magnesium triflate (Mg(CF3SO3)2) with the goal of developing electrolytes for the fabrication of solid-state devices. The resulting samples have been represented by the notation AgarnMg(CF3SO3)2, where n represents the percentage of the magnesium triflate salt proportion in the electrolyte samples. The samples investigated, with n between 0.00% and 37.56%, have been obtained as transparent and thin films. The samples have been characterized by conductivity measurements, thermal analysis, cyclic voltammetry, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The agar-based electrolytes were also tested as ionic conductor in an electrochromic device with the following configuration: glass/indium tin oxide (ITO)/WO3/agar-based electrolyte/CeO2–TiO2/ITO/glass.

Electroactive Poly(Vinylidene Fluoride-Trifluorethylene) (PVDF-TrFE) Microporous Membranes for Lithium-Ion Battery Applications

Poly(vinylidene fluoride-trifluorethylene) porous membranes were prepared by solvent evaporation at room temperature. The morphology of the membranes reveals an interconnected porous structure with porosity ranging from 72% up to 80%. The conductivity of the membranes and the LiClO4 uptake increases with increasing porosity. After uptake, the increase of the electrical conductivity is larger for the less porous membranes and the thermal stability of the electrical conductivity is increased.

Functional novel polymer electrolytes containing europium picrate

Abstract Novel polymer electrolytes based on either di-ureasil ormolytes or gelatin and containing europium picrate [Eu(pic)3] were prepared, characterised and compared by conductivity measurements, thermal analysis and electrochemical stability, X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopies. Small electrochromic devices (ECDs) with gelatin–europium salt optimised composition were assembled and characterised. The obtained results confirmed that these materials may perform as satisfactory multifunctional component layers in the field of ECD based devices.

Vibrational analysis of d-PCL(530)/siloxane-based hybrid electrolytes doped with two lithium salts

The present study has been focused on environmentally friendly sol–gel-derived electrolytes based on a di-urethane cross-linked d-PCL(530)/siloxane network [where d represents di, PCL identifies the poly(ε-caprolactone) biopolymer, and 530 is the average molecular weight in grams per mole] doped with a wide range of concentration of lithium perchlorate and lithium bis(trifluoromethanesulfonyl)imide. Fourier Transform Infrared and Raman spectroscopies have been applied to evaluate the extent of ionic association. Characteristic bands of the PCL(530) segments, of the urethane cross-links, and of the anions have been examined to gain insight into the cation/biopolymer, cation/anion, and cation/cross-link interactions. In both electrolyte systems, “free” ions and contact ions have been identified. The addition of salt modifies the hydrogen-bonded array of the host matrix, causing the destruction/formation of the urethane/urethane aggregates.

Synthesis and thermal behaviour of an amorphous solid polymer electrolyte

In this study the synthesis of an amorphous polymer network, poly[oxymethylene-oligo(oxyethylene)], designated as aPEO, is described. This polymer has been characterized by gel permeation chromatography, thermal analysis, conductivity measurements, evaluation of electrochemical stability and nuclear magnetic resonance spectroscopy. The synthetic procedure developed permits partial fractionation of the product of the polymerization reaction. This linear macromolecule appears to be a promising polymer for application in batteries and electrochromic devices since it provides access to an amorphous polymer structure with good mechanical properties and promising electrochemical behaviour.

Light responsive multilayer surfaces with controlled spatial extinction capability

Multilayer systems obtained using the Layer-by-Layer (LbL) technology have been proposed for a variety of biomedical applications in tissue engineering and regenerative medicine. LbL assembly is a simple and highly versatile method to modify surfaces and fabricate robust and highly-ordered nanostructured coatings over almost any type of substrates and with a wide range of substances. The incorporation of polyoxometalate (POM) inorganic salts as constituents of the layers presents a possibility of promoting light-stimuli responses in LbL substrates. We propose the design of a biocompatible photo-responsive multilayer system based on a Preyssler-type POM ([NaP5W30O110]14-) and a natural origin polymer, chitosan, using the LbL methodology. The photo-reduction properties of the POM allow the spatially controlled disruption of the assembled layers due to the weakening of the electrostatic interactions between the layers. This system has found applicability in detaching devices, such as the cell sheet technology, which may solve the drawbacks actually found in other cell treatment proposals.

Natural Membranes for Application in Biomedical Devices

Polymers from natural sources are particularly useful as biomaterials for medical devices applications. In this study, the results of characterization of a gelatin network electrolyte doped with europium triflate (Eu(CF3SO3)3) are described. The unusual electronic properties of the trivalent lanthanide ions make them well suited as luminescent reporter groups, with many applications in biotechnology. Samples of solvent-free electrolytes were prepared with a range of guest salt concentration. Materials based on Eu(CF3SO3)3 were obtained as mechanically robust, flexible, transparent, and completely amorphous films. Samples were characterized by thermal analysis (thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC), electrochemical stability, scanning electron microscopy (SEM), and photoluminescence spectroscopy.

Interpenetrating Polymer Networks Based on Poly(trimethylene carbonate) and poly(ethylene oxide) Blends Doped with Lithium Salts

Fundacao para a Ciencia e a Tecnologia (FCT) - POCI/QUI/59856/2004, POCTI/SFA/3/686), bolsa SFRH/BD/22707/2005 and SFRH/BD/38616/2007