resumo
The sol-gel process has been successfully combined with the "mixed cation" effect to produce novel luminescent and ion conducting biohybrids composed of a diurethane cross-linked poly(epsilon-caprolactone) (PCL530)/siloxane hybrid network (PCL stands for the poly(epsilon-caprolactone) biopolymer and 530 is the average molecular weight in gmol(-1)) doped with a wide range of concentrations of lithium and europium triflates (LiCF3SO3 and Eu(CF3SO3)(3), respectively) (molar ratio of ca. 50:50). The hybrid samples are all semicrystalline: whereas at n = 52.6 and 27.0 (n, composition, corresponds to the number of (C(=O)(CH2)(5)O) repeat units of PCL(530) per mixture of Li+ and Eu3+ ions) a minor proportion of crystalline PCL(530) chains is present, at n = 6.1, a new crystalline phase emerges. The latter electrolyte is thermally stable up to 220 degrees C and exhibits the highest conductivity over the entire range of temperatures studied (3.7 x 10(-7) and 1.71 x 10(-4) S cm(-1) at 20 and 102 degrees C, respectively). According to infrared spectroscopic data, major modifications occur in terms of hydrogen bonding interactions at this composition. The electrochemical stability domain of the biohybrid sample with n = 27 spans more than 7 V versus Li/Li+. This sample is a room temperature white light emitter. Its emission color can be easily tuned across the Commission Internationale d'Edairage (CIE) chromaticity diagram upon simply changing the excitation wavelength. Preliminary tests performed with a prototype electrochromic device (ECD) comprising the sample with n = 6.1 as electrolyte and WO3 as cathodically coloring layer are extremely encouraging. The device exhibits switching time around 50 s, an optical density change of 0.15, good open circuit memory under atmospheric conditions (ca. 1 month) and high coloration efficiency (577 cm(2) C-1 in the second cycle).
palavras-chave
ORGANICALLY MODIFIED SILICATES; ION-CONDUCTING ORMOLYTES; STATE LITHIUM BATTERIES; POLYMER ELECTROLYTES; POLY(ETHYLENE OXIDE); POLY(PROPYLENE OXIDE); THERMAL-PROPERTIES; HYBRID MATERIALS; METAL SALTS; ASSOCIATION
categoria
Science & Technology - Other Topics; Materials Science
autores
Fernandes, M; Nobre, SS; Rodrigues, LC; Goncalves, A; Rego, R; Oliveira, MC; Ferreira, RAS; Fortunato, E; Silva, MM; Carlos, LD; Bermudez, VD
nossos autores
Luís Carlos
Professor Catedrático
Maria Rute de Amorim e Sá Ferreira André
Professor Catedráticoagradecimentos
This work was supported by Fundacao para a Ciencia e a Tecnologia (FCT) and Projecto Estrategico - UI 686 - 2011-2012, PEst-C/QUI/UI0686/2011 and FEDER (PTDC/CTM/101324/2008). M.F., S.N., and L.C.R acknowledge FCT for grants (SFRH/BD/38530/2007, SFRH/BD/28739/2006, and SFRH/BD/38616/2007, respectively).