Preparation and characterization of highly proton-conductive composites composed of phosphoric acid-doped silica gel and styrene-ethylene-butylene-styrene elastomer

Citation
K. Hirata et al., Preparation and characterization of highly proton-conductive composites composed of phosphoric acid-doped silica gel and styrene-ethylene-butylene-styrene elastomer, J SOL-GEL S, 17(1), 2000, pp. 61-69
Citations number
17
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Material Science & Engineering
Journal title
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY
ISSN journal
0928-0707 → ACNP
Volume
17
Issue
1
Year of publication
2000
Pages
61 - 69
Database
ISI
SICI code
0928-0707(200001)17:1<61:PACOHP>2.0.ZU;2-C
Abstract
Highly proton-conductive elastic composites have been successfully prepared from H3PO4-doped silica gel and a styrene-ethylene-butylene-styrene (SEBS) block elastic copolymer. Ionic conductivities of the composites depended o n the concentration of H3PO4 and the heat treatment temperature of the H3PO 4-doped silica gel. It was found that H3PO4 added is present mainly as free orthophosphoric acid in the silica gel. The composite composed of H3PO4-do ped silica gel with a molar ratio of H3PO4/SiO2 = 0.5 heat-treated at tempe ratures below 200 degrees C and SEBS elastomer in 5 mass% showed a high con ductivity of 10(-5) S cm(-1) at 25 degrees C in an dry N-2 atmosphere. The water adsorption during a storage in 25% relative humidity at room temperat ure for 1 day enhanced the ionic conductivities of composites by about one order of magnitude. Lower conductivities obtained in the composite with the H3PO4-doped silica gel heat-treated at 250 degrees C for 1 h were due to t he formation of crystalline Si-3(PO4)(4). The temperature dependence of con ductivity of the composites was the Vogel-Tamman-Fulcher type, indicating t hat proton was transferred through a liquidlike phase formed in micropores of the H3PO4-doped silica gels. The temperature dependence of the modulus o f the composite was similar to that of the SEBS elastomer. The thermoplasti cally deforming temperature of the composite was around 100 degrees C, whic h was higher by 30 degrees C than that of the SEBS elastomer.