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 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 of the absorption bands of the mid-infrared spectra is presented. The spectral changes detected in the mid-infrared region and the modifications in the XRD patterns at increasing salt content show that PEOnEu(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 vC-O spectral region provide conclusive evidence that the Eu3+ ions are coordinated to the oxygen atoms of the polyether chains over the whole range of compositions studied. The photoluminescence spectra of the PEOnEu(pic)3xH2O electrolytes indicate that the Eu3+/ether oxygen complexation occurs with concomittant partial substitution of the water molecules from the cation coordination shell. The luminescence data obtainedFundação para a Ciência e a Tecnologia (FCT

Chitosan membranes containing micro or nano-size bioactive glass particles : evolution of biomineralization followed by in-situ dynamic mechanical analysis

A newfamilyofbiodegradablepolymer/bioactiveglass(BG)compositematerialshas emergedbasedontheavailabilityofnano-sizedbioactiveparticles.Suchnovelbiocompo- sites canhaveenhancedperformance,intermsofmechanicalpropertiesandbioactivity, and theycanbedesignedtobeusedinboneregenerationapproaches. In thiswork,membranesofchitosan(CTS)andchitosanwithbioactiveglass(BG)both micron andnanosizedparticles(CTS/mBG,CTS/nBG,respectively)werepreparedby solvent casting.Microstructuralandmechanicalpropertieswereevaluatedinorderto compare theeffectsoftheincorporationofmicro(mBG) andnano(nBG)particlesinthe chitosan matrix. In vitro bioactivity testswereperformedtocharacterizetheapatitelayer that isformedonthesurfaceofthematerialafterbeingimmersedinsimulatedbodyfluid (SBF). Thebiomineralizationprocessonthebiomaterialswasalsofollowedusingnon- conventionaldynamicmechanicalanalysis(DMA),bothonlineandoffline.InsuchDMA experiments,thechangeinthestoragemodulus, E0, andthelossfactor,tan d, were measured asafunctionoftheimmersiontimeinSBF.TheresultsdemonstratedthatCTS/ nBG membranespossessenhancedmechanicalpropertiesandhigherbioactivityin comparisonwiththeCTS/mBG membranes.SuchresultssuggestthepotentialofnBGfor the developmentofbioactivecompositesforboneregenerationapplications.This work was financially supported by Foundation for Science and Technology (FCT) by the projects PTDC/QUI/69263/2006, PTDC/CTM-BPC/112774/2009 and, through the scholarship SFRH/BD/64601/2009 granted to Sofia G. Caridade. The authors acknowledge Dr D. Mohn and Prof. W. Stark (Em Zurich) for providing the nBG particles used

Sol-gel preparation of a di-ureasil electrolyte doped with lithium perchlorate

Solid polymer electrolytes (SPEs) synthesized by the sol-gel process and designated as ormolytes (organically modified electrolytes), have been prepared through the incorporation of lithium perchlorate, LiClO4 into the U(2000) organic-inorganic hybrid network. Electrolytes with lithium salt compositions of n (where n indicates the number of oxyethylene units per Li+ ion) between ∞ and 0.5 were characterized by conductivity measurements, cyclic voltammetry at a gold microelectrode, thermal analysis and spectroscopic techniques. The conductivity results obtained suggest that this system offers a quite significant improvement over previously characterized analogues doped with lithium triflate.Fundação para a Ciência e a Tecnologia (FCT) - POCI/QUI/59856/2004.Fundação Calouste Gulbenkian - MMS.Universidade do Minho.Universidade de Trás-os-Montes e Alto Douro

Spectroscopic and structural studies of di-ureasils doped with lithium perchlorate

Di-urea cross-linked POE/siloxane hybrid ormolytes (di-ureasils) doped with a wide concentration range of lithium perchlorate trihydrate (LiClO4·3H2O) (200 ≥ n ≥ 0.5, where n expresses the salt content in terms of the number of ether oxygen atoms per Li+ ion) have been analysed by Fourier transform infrared and Raman (FT-IR and FT-Raman, respectively) spectroscopies and X-ray diffraction (XRD). The results obtained lead us to conclude that the xerogels with n ≥ 5 are totally amorphous. At n ≤ 1 free salt is observed. “Free” ClO4− ions appear to be the main charge carriers at the conductivity maximum located within the 25 ≤ n ≤ 8 composition range of this family of ormolytes. At n = 15 ClO4− ions coordinated in mono/tridentate (C3v symmetry) and bidentate (C2v symmetry) configurations were detected. In salt-rich samples with n < 15 there is a marked tendency for ionic association. The resulting decrease that occurs in the concentration of “free” ions is consistent with the observed significant decrease of the ionic conductivity. The analysis of the “amide I” and “amide II” regions provided solid proof that the Li+ ions bond to the urea carbonyl oxygen atoms over the entire range of salt concentration studied.Fundação para a Ciência e Tecnologia (FCT

Study of sol-gel derived di-ureasils doped with zinc triflate

Prova tipográfica (In Press)A publicar em "Solid States Sciences".Zinc triflate (Zn(CF3SO3)2)-doped sol-gel derived di-urea cross-linked POE/siloxane ormolytes (designated as di-ureasils) with ∞ > n ≥ 1 (where the salt content is expressed as n, the molar ratio of oxyethylene moieties to Zn2+ ions) were investigated. The hybrids with n ≥ 5 are entirely amorphous; those with n > 10 are thermally stable up to approximately 305 ºC. The siliceous network of representative samples (n = 200 and 10) is essentially composed of (SiO)3Si(CH2)- environments and is thus highly branched. The distance between the structural units in samples with 200 ≥ n ≥ 10 and n ≤ 7 is 4.2 and 4.3 Å, respectively. The estimated interdomain distance is 11 and 13 Å for xerogels with 200 ≥ n ≥ 20 and n ≤ 10, respectively. At n = 1 a crystalline POE/Zn(CF3SO3)2 complex of unknown stoichiometry is formed. The conductivity maxima are located at n = 60 (3x10-6 S cm-1) and n = 20 (7x10-5 S cm-1) at 30 and 100 ºC, respectively.Fundação para a Ciência e a Tecnologia - POCTI/P/CTM/46780/03; SFRH/BD/13559/03

Di-ureasil ormolytes doped with Mg2+ ions : part 1: morphological, thermal and electrochemical properties

Poly(oxyethylene)(POE/siloxane-based materials incorporating magnesium triflate were prepared by the sol-gel process. The host Class II hybrid matrix (di-ureasil) employed was composed of a siliceous framework to which short POE chains were covalently bonded through urea linkages. Ormolytes with salt composition ranging from 500 to 1 were characterised. The nanohybrid with n = 20, thermally stable up to 360ºC, exhibited the highest ionic conductivity. The electrochemical stability of this material was found to span -3 to +2 volts.Fundação para a Ciência e Tecnologia - POCTI/P/CTM/33653/00; SFRH/BD/13559/03; POCTI/P/CTM/46780/03

Mg2+-doped poly(ε-caprolactone)/siloxane biohybrids

Electrolytes based on a poly(ε-caprolactone) (PCL)/siloxane organic/inorganic host framework doped with magnesium triflate (Mg(CF3SO3)2) were synthesized by the sol-gel process. In the biohybrid matrix short PCL chains are covalently bonded via urethane linkages to the siliceous network. In this study the salt content of samples was identified using the conventional n notation, where n indicates the number of (C(=O)(CH2)5O) PCL repeat units per Mg2+ ion. Materials with compositions ranging from n=∞ to 2 were prepared. The only composition prepared that is not entirely amorphous is that with n = 1. Xerogels with n ≥ 7 are thermally stable up to up to at least 200 ºC. The most conducting ormolyte of the series is that with n = 26 (5.9x10-9 and 9.8x10-7 Scm-1 at 24 and 104 ºC, respectively).Fundação para a Ciência e Tecnologi

Structure, thermal properties, conductivity and electrochemical stability of di-urethanesil hybrids doped with LiCF3SO3

Variable chain length di-urethane cross-linked poly(oxyethylene) (POE)/siloxane hybrid networks were prepared by application of a sol-gel strategy. These materials, designated as di-urethanesils (represented as d-Ut(Y’), where Y’ indicates the average molecular weight of the polymer segment), were doped with lithium triflate (LiCF3SO3). The two host hybrid matrices used, d-Ut(300) and d-Ut(600), incorporate POE chains with approximately 6 and 13 (OCH2CH2) repeat units, respectively. All the samples studied, with compositions ∞ > n ≥ 1 (where n is the molar ratio of (OCH2CH2) repeat units per Li+),, are entirely amorphous. The di-urethanesils are thermally stable up to at least 200 ºC. At room temperature the conductivity maxima of the d-Ut(300)- and d-Ut(600)-based di-urethanesil families are located at n = 1 (approximately 2.0x10-6 and 7.4x10-5 Scm-1, respectively). At about 100 ºC, both these samples also exhibit the highest conductivity of the two electrolyte systems (approximately 1.6x10-4 and 1.0x10-3 Scm-1, respectively). The d-Ut(600)-based xerogel with n = 1 displays excellent redox stability.Fundação para a Ciência e a Tecnologia (FCT

Di-urea cross-linked poly(oxyethylene)/siloxane ormolytes for lithium batteries

Poly(oxyethylene)( POE)/siloxane hybrids (di-ureasils) doped with a wide concentration range of lithium triflate were investigated. The host matrix of these materials (d-U(2000)) is a sol-gel derived siliceous network to which POE chains with about 40 repeat units are bonded through urea linkages. Xerogels with n between 500 and 5 (where n is the molar ration of OCH2CH2 repeat units to lithium íons) were obtained as amorphous monoliths thermally stable up to at least 340ºC. A crystalline POE/LiCF3SO3 complex was detected spectroscopically in samples with compositions of n less than 10. Below 90ºC the ormolyte with n = 20 exhibits the highest ionic conductivity of the series characterized. The redox stability of this material is about 4.1 volts

Sol-gel derived Li+-doped poly(ε-caprolactone)/siloxane biohybrid electrolytes

Electrolytes based on a poly(ε-caprolactone) (PCL)/siloxane organic/inorganic host framework doped with lithium triflate (LiCF3SO3) were synthesised through the sol-gel process. In this biohybrid matrix short PCL chains are covalently bonded via urethane linkages to the siliceous network. Samples with salt composition n (molar ratio of PCL repeat units per Li+ ion) ranging from ∞ to 0.5 were investigated. All the ormolyte materials analysed are amorphous. Xerogels with n > 0.5 are thermally stable up to about 300°C. The most conducting ormolyte of the series is that with n = 0.5 (1.6×10−7 and 3.2×10−5 Ω−1 cm−1 at 25 and 100°C, respectively). This sample is electrochemically stable between −1 and 6 V versus Li+.Fundação para a Ciência e Tecnologia - POCTI/P/CTM/33653/00, SFRH/BD/13559/03, POCTI/P/CTM/46780/03.Fundação para a Ciência e a Tecnologia (FCT