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

• Main Author: Gonçalves, M. C.
• Publication Date: 2010
• Other Authors: Zea Bermudez, V. de, Silva, Maria Manuela, Smith, Michael John, Morales, Enrique, Ferreira, R. A. Sá, Carlos, L. D.
• Format: Article
• Language: eng
• Source: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Download full: http://hdl.handle.net/1822/11645
• topic: Diurethanesils; Llthium triflate; Thermal analysis; Complex impedance spectroscopy; Cyclic voltammetry; Electrochromic devices; Lithium triflate; DSC; TGA; XRD; Complex impedance; Science & Technology

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.