title: Quenched microemulsions: a new route to proton conductors.
abstract: Solid-state proton conductors operating under mild temperature conditions (T < 150 °C) would promote the use of electrochemical devices as fuel cells. Alternatives to the water-sensitive membranes made of perfluorinated sulfonated polymers require the use of protogenic moieties bearing phosphates/phosphonates or imidazole groups. Here, we formulate microemulsions using water, a cationic surfactant (cetyltrimethyl ammonium bromide, CTAB) and a fatty acid (myristic acid, MA). The fatty acid acts both as an oil phase above its melting point (52 °C) and as a protogenic moiety. We demonstrate that the mixed MA-CTA film presents significant proton conductivity. Furthermore, bicontinuous microemulsions are found in the water-CTAB-MA phase diagram above 52 °C, where molten MA plays both the role of the oil phase and the co-surfactant. This indicates that the hydrogen-bond rich MA-CTA film can be formulated in the molten phase. The microemulsion converts into a lamellar phase upon solidification at room temperature. Our results demonstrate the potential of such self-assembled materials for the design of bulk proton conductors, but also highlight the necessity to control the evolution of the nanostructure upon solidification of the oil phase.
authors.affiliation: CEA, IRAMIS, NIMBE, CNRS, UMR3299 SIS2M CEA-CNRS, Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire, F-91191 Gif-sur-Yvette, France. david.carriere@cea.fr.
authors.forename: Cecile
authors.initials: C
authors.lastname: Noirjean
authors.forename: Fabienne
authors.initials: F
authors.lastname: Testard
authors.forename: Jacques
authors.initials: J
authors.lastname: Jestin
authors.forename: Olivier
authors.initials: O
authors.lastname: Taché
authors.forename: Christophe
authors.initials: C
authors.lastname: Dejugnat
authors.forename: David
authors.initials: D
authors.lastname: Carriere